The Fisheries Blog

Through the Ears of a Fish

2014-01-13T07:23:00.000-05:00

by Ed Kluender, guest blogger

Ask a fish its age or where it's been and what it ate for lunch, and chances are it couldn't tell you. It could probably hear your question, though, with the help of its inner ear bones, called otoliths. Otoliths are one of the most useful tools in a fish biologist’s toolbox. When removed and studied, otoliths can reveal a fish’s age, growth rate, and some history of where it’s been.

Otoliths are similar to the bones in human inner ears. They are three pairs of small stone-like structures, called the lapilli, sagittae, and asterisci (singular: lapillus, sagitta, asteriscus). Otoliths are suspended in fluid-filled sacs, and as in humans, help with balance and orientation.

Inner ear structure and otolith location in typical teleost fish. The sagittae and lapilli are the two typically used for aging fish. Source: David Secor, University of Maryland.

Otoliths grow throughout a fish’s life, and are formed by layers of calcium carbonate that are laid down at different rates, depending on metabolic rate. Slower metabolic rates during the winter form denser layers (the opaque zone), while high metabolic rates in spring and summer form less dense layers (the translucent zone). This makes the otoliths look like an onion, with the opaque bands corresponding to slower growth appearing as dark rings.

Because each opaque band represents a year of growth, scientists can use otoliths to estimate a fish’s age. Then, using the fish’s total length and proportional diameters of each opaque zone to the total diameter of the otolith, we can estimate the fish’s length at any age and thus its growth rate.

Left: Alternating opaque and translucent zones reveal a fish’s age. Right: To determine the age of a fish in years, otoliths are cut into thin wafers, mounted on a slide, and the rings are counted like tree rings. This cross-section from a Freshwater Drum reveals the fish to be about 74 years old.

But age and growth is just one of many uses of otoliths. Because different types of food items and aquatic environments contain unique isotopic signatures, the chemical structure of otoliths can reveal where a fish has been and what it has eaten at any point in its life. This field of study is called microchemistry, and can also reveal other environmental conditions at any life stage, like salinity and temperature.

The size and shape, or morphology, of otoliths can reveal more information about population structure and environmental conditions. Otoliths have even been useful in recent climate change research . Some research even shows that fish can hear quite well with their otoliths, and sense the direction and nature of the sound.

Otoliths contain all of this information, even in larval fishes. The metabolism of a larval fish fluctuates on a daily basis in response to water temperature and daylight. At night, metabolism slows, which causes the formation of a minute opaque zone. With the aid of a microscope, we can look at the tiny otoliths – some as small as 0.1 mm – and count the number of daily rings to estimate the day at which the larvae hatched. After that, we can estimate the fish’s daily growth rate since hatching.

A larval Flannelmouth Sucker before otolith extraction. Precise total length measurements are necessary to calculate the most accurate growth rate possible. In fish this small, the tiny otoliths must be extracted with very fine tools under a microscope. Source: Colorado State University.

From there, based upon the knowledge of how long different species must incubate as eggs, we can back-calculate the exact day the eggs were spawned and fertilized and how fast they have developed since then. Daily records of weather, temperature, and hydrology create a context that tells us quite a lot about the needs of different fish species, and the effects they have had on growth.

Otolith extracted from the larval Flannelmouth Sucker pictured above. At 17 days old, a total length of 15.96 mm tells us that this fish was growing 0.94 mm per day during this critical stage in development. This fish was part of a sample collected from a stream in which water is diverted for irrigation. Source: Colorado State University

This information is very valuable to scientists and land managers. Because the habitats and water conditions in which fish spawn, incubate, and rear their young are very important to successful recruitment into the population, care must be taken to keep that habitat suitable for optimum growth rate.

Seemingly simple actions like diverting water for agriculture or power plant cooling result in the water returning to its source with a very different temperature, turbidity, and chemistry that can prevent successful reproduction.

Please see an earlier post by The Fisheries Blog for more information about otoliths.

Be sure to like The Fisheries Blog on Facebook, follow us on Twitter (@FisheriesBlog), and feed the fish at the bottom of the page.

References

Campana, S. E. 1999. Chemistry and composition of fish otoliths: pathways, mechanisms and applications. Marine Ecology Progress Series. 188:263-297

Popper, A. N. and Z. Lu. 2000. Structure-function relationships in fish otolith organs. Fisheries Research. 46:15-25

Q-tip anyone?

2014-01-06T02:04:00.000-05:00

By Dana Sackett

You may have come across a video or two (or ten) of sharks munching down on dead whales and it’s easy to understand how a few sharks may get excited over encountering all that easily acquired energy-rich blubber. However, sharks are not the only ones that can benefit from these large dead mammals. Scientists can benefit too, but less so from their blubber than from their earwax. Now your initial reaction may be, “eww” but this is a true boon for scientists; especially because recent finding show how plugs of earwax can tell us about the whale’s lifetime exposure to pollution and more.

Dead blue whale. Source

Scientists have routinely used plugs of whale earwax to determine a whale’s age. This process is possible because earwax is laid down seasonally in layers that occilate between dark and light each representing 6 months of life; dark during the feeding season and light during the fasting season when whales migrate.

Recently, however, scientist have discovered that whale earwax is even more useful than they originally thought because pollutants in the whales body are archived with each new layer of fat and wax that is laid down in their ear. With this new discovery scientists can determine which pollutants the whale had been exposed to over its lifetime and at what age it was exposed.

This diagram shows an earplug in a blue whale skull. The bacon-like image (D) is a close-up of the earplug. Images courtesy Michelle Berman-Kowalewskic, Santa Barbara Museum of Natural History. Source

In the recent groundbreaking study that discovered this new method the authors sampled a 10in long plug of earwax (panel B in the picture above) from an endangered blue whale that was hit by a ship off the coast of California in 2007. The results showed that the male was approximately 12 years old and had been exposed to high levels of persistent organic pollutants (like DDT) and pesticides in the first 6 months of life; likely passed on from the mother in the womb and though nursing. Many marine mammals have been known to pass contaminants built-up over time to offspring, with the highest concentrations going to the first born. This whale accumulated 20% of its lifetime burden from its mother.

The male blue whale whose earwax was used in the discussed study. Source

Mercury was also noted to show high spikes in years 5 and 10 and the authors suggested that these spikes may coincide with migration that brought the whale close to the west coast of the US where contamination would have been higher than in the open ocean or along other less polluted land masses.

Even more, contaminants are not the only chemicals recorded in these massive earplugs, hormones are also sequestered in the wax. Increased testosterone, in the blue whale mentioned above, suggested that he reached sexual maturity around 10 years of age. This increase also coincided with an increase in stress hormones, which could be linked to the stress of finding or fighting for a mate among much larger and older males.

The earplug from a female bowhead whale extracted in 1964. Analyzing earwax from older samples will help show how contaminant levels have changed in our oceans over time. Source

With super earwax that can record so much information over the lifetime of an animal and even provide information on the general health of our oceans, I am tempted to skip the “eww” factor and move on to “oooo” ….. for whale earwax at least.

References:

http://www.newscientist.com/blogs/shortsharpscience/2012/04/whale-ears.html

http://www.nbcnews.com/science/whales-life-story-recorded-its-ear-wax-8C11167240

Krahn MM, Hanson MB, Schorr GS, Emmons CK, Burrows DG, Bolton JL, Baird RW, Ylitalo GM. 2009. Effects of age, sex and reproductive status on persistent organic pollutant concentrations in “Southern Resident” killer whales. Marine Pollution Bulletin 58:1522-1529.

Trumble SJ, Robinson EM, Berman-Kowalewski M, Potter CW, Usenko S. Blue whale earplug reveals lifetime contaminant exposure and hormone profiles. PNAS 110:16922-16926.

Ylitalo GM, Matkin CO, Buzitis J, Krahn MM, Jones LL, Rowles T, Stein JE. 2001. Influence of life-history parameters on organochlorine concentrations in free-ranging killer whales (Orcinus orca) from Prince William Sound, AK. The Science of the Total Environment 281:183-203.

Yordy JE, Wells RS, Balmer BC, Schwacke LH, Rowles TK, Kucklick JR. 2010. Life history as a source of variation for persistent organic pollutant (POP) patterns in a community of common bottlenose dolphins (Tursiops truncates) resident to Sarasota Bay, FL. Science of the Total Environment 408:2163-2172.

Reflections on 2013

2013-12-30T08:29:00.001-05:00

It has been a great 2013 for The Fisheries Blog as we've seen our audience grow, largely as our topics and writers have increased. To finish up the year, we will borrow a concept from others and give you what you are truly craving—the best of 2013!

But before we hit the highlights, listen to Patrick Cooney, a writer with The Fisheries Blog, give a presentation about how we approach scientific communication. This was presented at the American Fisheries Society conference in September 2013.

Click Here to watch the Presentation!

And once you are done with the video and looking for more before the New Year's ball drops, take a look at some of your favorite stories we covered in 2013!

Nemo Causes a News Uproar
"Leave it to a scientist to ruin Finding Nemo!" These were actually some of the kinder words we received regarding Patrick Cooney's discussion on how a real life Finding Nemo might play out...

Fish on Fire
With the increases of wildfire in the news, Steve Midway explained how these burning landscapes impacted stream inhabitants to many interested readers.

Antibiotics
Just when antibacterial claims are again making the news, our very own Dana Sackett provided us with a thoroughly interesting look at the dangers of antibiotics.

The Importance of Fish
Ok, we know you all don't need to be reminded how important fish are...but once more won't hurt. Especially when the reminder comes in the form of this excellent overview by our brand-new blogger Abby Lynch.

Val Kells Stops By
Among all of Brandon People's excellent reporting from this past year, it's hard to beat his interview with one of the best fish illustrators in the business.

And thanks again to all our guest blogger that have contributed over the past year: Tobey Curtis, Craig Springer, Ed Kluender, Erin Miller, Dr. Lindsay Campbell, Gus Engman, Leigh Anne Harden, Kristine Stump, and Byron Levan.

Once again, have a great New Year, everyone, and we look forward to more fisheries news in 2014!
Dana, Abby, Brandon, Patrick, and Steve

Happy Holidays from The Fisheries Blog!

2013-12-23T01:51:00.002-05:00

Happy Holidays from The Fisheries Blog!

Dr. Abigail Lynch, Patrick Cooney, Brandon Peoples, Dr. Dana Sackett, and Dr. Steve Midway thank you for another great year! Please check in next Monday for highlights on our articles and guests from 2013.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

Dolphin Deaths a Boon for Sharks?

2013-12-16T09:45:00.003-05:00

By Tobey Curtis, Guest Blogger

It's been a tough year to be a dolphin. The Miami NFL football players aren’t the only dolphins making headlines lately. Over the last year there have been hundreds of mysterious dolphin deaths along the US Atlantic coast. By late summer, the National Oceanic and Atmospheric Administration (NOAA) had declared two “Unusual Mortality Events” for bottlenose dolphins, one in the Mid-Atlantic (New York to South Carolina), and one in Florida’s Indian River Lagoon. To date, nearly 800 dolphin deaths have been confirmed in the Mid-Atlantic region, and over 70 in the Indian River Lagoon.

Number of dolphin strandings by state for 2013 (red) and the 2007-2012 average (blue). Source: NOAA Fisheries Service

While investigations are still underway, possible culprits in the mass mortality events have been identified. A rare viral infection called cetacean morbillivirus seems to be behind most of the dolphin deaths in the Mid-Atlantic, and the epidemic now appears to be spreading to the southeast coast. However, the causes of the mortalities in the Indian River Lagoon have been harder to identify.

Regardless of the cause, there’s been a heck of a lot of dead and dying dolphins scattered along the coast this year. Now this may sound tragic (and smelly) to some, but to sharks…it’s been a bonanza! Sharks love dolphins...like football fans love chicken wings. Dolphin flesh is full of high-calorie fatty tissues – the kind of fuel that can meet a shark’s metabolic demands for weeks.

A half-dolphin carcass that washed ashore in South Carolina in November is likely a victim of both morbillivirus and a white, tiger, or bull shark. Photo credit: Mark Gray via Southern Fried Science.

Due to their size, agility, and intelligence, dolphins are typically a challenge for sharks to hunt. Only a handful of larger shark species are considered regular predators of dolphins, including tiger, bull, dusky, and white sharks. And even these sharks will tend to target easier prey like juveniles and sick or injured individuals. Other shark species don’t tend to hunt live dolphins, but will certainly scavenge their carcasses when available. Despite the caloric benefits of eating a dolphin, sharks can only expect to have occasional opportunities to successfully consume them. That is, unless there is a widespread mortality event that creates a sick dolphin buffet. And when that happens, you can expect to find a lot of fat and happy sharks.

A hefty (not pregnant) sub-adult bull shark caught and released near an Indian River Lagoon inlet during Fall 2013. It’s very possible that this fat shark had been chowing on deceased bottlenose dolphins. Photo credit: Matthew Scripter.

Reports from South Carolina to Florida indicate that sharks are taking full advantage of the Unusual Mortality Events. According to biologists at the Hubbs-SeaWorld Research Institute in Florida, the majority of stranded dolphins they examined this year showed indications of shark bites. The prevalence of shark bites was much higher than in previous years. Some dolphins have been simply bit in half. Research is ongoing to help differentiate between dolphins that were scavenged by sharks after they died, and those that were bitten while still alive.

The major areas where white sharks have been documented to bite dolphins ranked from most common (1) to least common (6). Sharks will tend to attack live dolphins from below and/or behind, avoiding the range of the dolphin’s sonar field. Source: Long and Jones (1996).

While marine mammal lovers may mourn the losses of these dolphins, many sharks, with full bellies, are thankful for their sacrifice. This unusual abundance of high-quality food will likely support increased survival and growth of the sharks fortunate enough to capitalize on the event. Though a temporary phenomenon, sharks will take advantage of these opportunities as long as they continue. The ocean’s circle of life may be harsh at times, but sharks are doing their part to recycle the remnant carbon and stored energy of these ex-dolphins back into the marine food web. This is all part of a shark’s role in helping maintain healthy coastal ecosystems.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

Tobey is a PhD Candidate, School for Marine Science and Technology, University of Massachusetts-Dartmouth

Follow Tobey on Twitter @Mojoshark

References:

Heithaus, MR. 2001. Predator-prey and competitive interactions between sharks
(order Selachii) and dolphins (suborder Odontoceti): a review. Journal of the Zoological Society of London 253:53-68.

Hubbs-SeaWorld Research Institute.

Long, DJ and RE Jones. 1996. White shark predation and scavenging on cetaceans in the eastern North Pacific Ocean. Pp. 293-307 in Klimley, AP and DG Ainley (eds), Great White Sharks: The Biology of Carcharodon carcharias. Academic Press, San Diego.

NOAA Fisheries Service Office of Protected Resources Unusual Mortality Event information.

One Fish, Two Fish, Where Fish for Whitefish?

2013-12-09T08:37:00.002-05:00

by Abigail Lynch

Designing a climate change decision-support tool for Great Lakes Lake Whitefish
Imagine you are playing a game of Monopoly and are investing wisely for the future. You have numerous hotels on “Boardwalk” and are raking in the dough any time another player lands on your valuable property. Then, the rules of the game unexpectedly change. “Baltic Place” is the hot commodity and all of your painstaking investments in “Boardwalk” are for naught. Now, imagine this is not a game and your actual livelihood and family depend on your success.

Currently, the Great Lakes Lake Whitefish fishery is the most economically valuable commercial fishery in the upper Great Lakes. But, like the modified Monopoly, this fishery could face new “rules of the game” from climate change. My dissertation research developed a decision-support tool to ensure that the fish, the fishery, and the livelihoods dependent upon them remain sustainable in the face of climate change.

“A better fish cannot be eaten!”
Lake Whitefish, a member of the salmon family, are found in coldwater lakes throughout much of northern North America. Like many salmon species, they are highly valued as food fish: fresh fillets, smoked fillets, frozen fillets, fish cakes, spread, and sausage. Lake Whitefish have been a staple of native communities in the Great Lakes for thousands of years and were a particular favorite of early French explorers—one even wrote that “a better fish cannot be eaten!” They are a favorite still today; over 15 million pounds of Lake Whitefish are consumed each year in the Great Lakes region alone.

Aiming for 20/20 vision of lake whitefish recruitment
To reach someone’s dinner plate, a Lake Whitefish must survive a treacherous journey from an egg to a larvae to a juvenile and, finally, recruit to the fishery. Ultimately, we want to know how many Lake Whitefish enter the fishery so that we can determine how many can be harvested without negatively impacting future populations and harvest. But, it is next to impossible to know how many Lake Whitefish are actually out there. So, we estimate the population size using mathematical modeling.

You can think of mathematical modeling of fish populations like a visit to the eye doctor. For many of us, perfect 20/20 vision is as unobtainable as knowing true population abundance is for fishery managers. But, with corrective lenses and modeling approaches, we can get pretty close to estimating (or seeing) those realities. Like adjusting the lenses in an eye exam, including biologically relevant variables in the model can often improve our ability to predict fish populations.

My dissertation research did just that. I examined climate factors, specifically temperature, wind, and ice cover, which have been shown to influence recruitment of Lake Whitefish to the commercial fishery. Because Lake Whitefish spawn in the fall and hatch as larvae in the spring, these time periods are particularly critical to the survival of Lake Whitefish. I used historical data to model how changes in these climate variables affected recruitment.

Could warmer temperatures be good for a coldwater fish?

Earlier research has observed positive relationship between recruitment and spring temperatures and ice cover and a negative relationship between recruitment and fall temperatures and fall wind speed. My research confirmed these same patterns. Warmer spring temperatures may improve survival of larval Lake Whitefish, if food resources are available, and increase Lake Whitefish production in the Great Lakes. However, warmer fall temperatures, more wind, and less ice cover may inhibit egg survival and, consequently, Lake Whitefish production.

The relationship between climate variables and Lake Whitefish recruitment has significant implications for the fishery in the context of climate change. By the end of this century, the Great Lakes region will be warmer, windier, with less ice cover. Surface temperatures for the Great Lakes, for example, are expected to increase by as much as 7°F. So, is this just another “doom and gloom” climate change story where a species will be ousted by habitat changes? Or, perhaps could warmer temperatures be good for this coldwater fish?

Using the climate-recruitment model, I was able to project anticipated impacts on Lake Whitefish recruitment using my climate-recruitment model and a downscaled climate model developed for the Great Lakes for the 1836 Treaty Waters of Lakes Huron, Michigan, and Superior. The 1836 Treaty Waters sustain a highly productive Lake Whitefish fishery, approximately 25% of the whole fishery in the upper Great Lakes. Recruitment projections varied between management units; some had up to a 50% decline and others had as much as a 220% increase. Overall, my research suggests that there is potential for increased Lake Whitefish recruitment in the Great Lakes with climate change and some shift in the distribution of the fishery.

Predicting the Monopoly board
These potential changes in Lake Whitefish populations have significant repercussions for fishermen and the communities dependent upon this fishery. Returning to the Monopoly analogy, if you could predict changes to the game, you would change your strategy and invest differently. Likewise, my research aims to help the Lake Whitefish fishery adapt to anticipated climate change. I hope my climate-recruitment model and projections will serve as a decision-support tool to assist fishermen and fishery managers. This tool, which is housed on the Michigan Sea Grant website, will tell fishermen if it’s better to give up on the “Boardwalk” fishery locations and focus their investments on “Baltic Place” for a more sustainable and prosperous fishery. Because, ultimately, who doesn’t want to win Monopoly?

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

For more information
-Abby's dissertation defense webinar (Adobe Connect or YouTube)
-Michigan Sea Grant Lake Whitefish-climate change website

Sympathy for the ugliest animal in the world

2013-12-02T07:19:00.001-05:00

by Brandon Peoples

Meet the blobfish, one of my favorite underwater underdogs. The blobfish lives in incredibly deep water (up to 4,000 feet!) off the coast of Australia, where it whiles away the days hovering over the bottom and eating whatever drifts in front of it.

Blobfish aren't exactly the most charming fish in the sea. Source

The blobfish has a face only a mother could love. In fact, it’s downright ugly.

Its thick, fleshy lips are curved into a constant frown and its body looks like it’s made out of bleached-out cherry Jell-O. On top of that, it’s got small beady eyes, stubby little pectoral fins, and a nose that looks like a dripping extension of its forehead.

Everyone loves to hate the blobfish. Its sappy looking image is plastered all over the internet as the subject of countless ridiculous memes. I won’t give them the dignity of a link, but you can Google them.

Press for the blobfish hasn’t been all bad, however. It was recently voted World’s Ugliest Animal, and is now the mascot for the Ugly Animal Preservation Society—a group dedicated to raising awareness for the conservation of low-profile threatened species.

Positive attention for the blobfish is coming at a good time, too. This species is on the decline due to bycatch from deep sea trawling. Although blobfish are basically inedible, they are often captured and inadvertently killed in the hunt for food fish.

Michael Hearst wrote a song for the blobfish on Songs for Unusual Creatures. Source

But because this fish’s charm is an acquired taste, society has been slow to jump on the “save the blobfish” bandwagon. So, below I list a few of the blobfish’s more deplorable traits, and make the case that this fish is actually an impressive gem of natural history that should be protected.

It’s just a blob of goo. That’s because the blobfish is built to minimize its energy usage in an environment where pressure can be a dozen times that of sea level. The blobfish has very little muscle…and that’s a good thing. Blobfish flesh is actually a gelatinous mass, just slightly more dense than water. This enables the blobfish to hold its vertical position without investing in a swim bladder.

That pale pink skin gives me the creeps. That’s camouflage! Red light is the first in the visible spectrum to be filtered by water. In the darkness of the deep, the blobfish is virtually invisible.

How about spreading a more endearing blobfish meme?

I don’t trust those beady little eyes. In the deep sea, eyes are overrated. Blobfish spend most of their time in the dark, so they can rarely see their prey. Instead, they rely on other senses to catch a meal.

But it’s so lazy—it just sits there. Hey, why spend all that energy chasing down prey when you can just sit back and wait for it to come to you? What do you expect from a fish with hardly any muscle mass?

So, next time you see one of those silly memes, think of how well the blobfish is adapted to its deep sea environment. Hopefully, we can keep this fish on the “World’s Ugliest Animals” list, and off the list of extinct species.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

Thanksgiving Fish: The Missing Ingredient

2013-11-25T08:08:00.000-05:00

By Steve Midway

As many of us in the U.S. prepare for the Thanksgiving holiday later this week, a litany of traditional foods comes to mind: turkey, stuffing, mashed potatoes, cranberry sauce, pumpkin pie. Indeed—in some form or another—many of these foods were present at the first Thanksgiving. However, conspicuously absent from both the traditional shopping list and holiday table are fish and shellfish, which were most certainly featured prominently at the first Thanksgiving.

Pass the eel, please. (Source)

While perhaps not the centerpiece of the first Thanksgiving, fish and shellfish were abundant in coastal Colonial waters and relatively easy to harvest—meaning they were already part of the historic diet. Mussels and clams were a simple collect, and a number of other nearshore and shallow-water shellfish, including lobster, likely made the table. Middens—mounds of old shells—have been dated for archaeological purposes and indicate that shellfish consumption predates any colonists.

Colonists may have brought with them some nets, but it's less clear how much (deep-water) fishing early settlers did. In his book Cod: A Biography of the Fish that Changed the World, Mark Kurlansky discusses the the importance of cod fishing in the founding and settling of North America, so it's clear that fishing was taking place nearby even if Cod didn't make the Thanksgiving menu. Daniel Schmidt summarizes fishing efforts in colonial Virginia and provides evidence for seines and hook-and-line fishing, which may likely have also been used in New England.

Fishhooks found at Fort James, dating back to colonists. (Schmidt 2006)

One method of capturing fish that was particularly effective was taught to the colonists by the Native Americans. This method is often referred to as a fish trap or fish weir. The premise is simple: create an enclosure (often baited) that funnels fish in, but from which fish typically cannot escape. Large, old stone weirs are still visible on some rivers, and pound net fishing is just a larger and slightly more elaborate version of the same principle. For a basic idea of how a simple fish trap works, check out the video below!

As you can see, fishing was a well-developed activity by the time the colonists arrived in North America, and they quickly took it up. Spearfishing, fish traps, and shellfish collection likely resulted in plenty of eels, sturgeon, and bivalves being served at the first Thanksgiving. By all means, continue the tradition of turkey and stuffing, but why not add a little smoked eel for that authentic Thanksgiving experience?

If you have fish at your traditional Thanksgiving feast, in the comments below let us know what you serve!

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

Top 5 Most Poisonous Fish!

2013-11-18T01:40:00.001-05:00

By Dana Sackett

Many TV shows and nature guides have been dedicated to educating the public on the most poisonous and venomous spiders, snakes and even frogs, but what about fish? Unlike spiders or snakes, we rarely hear about which fish are the most poisonous (or venomous). This week we are dedicating our blog post to these hazardous fish.

(Cooney)

First though let’s clarify some terminology. Poisonous and venomous are terms often used interchangeably but they have different meanings. A venomous animal has a means of injecting their toxin into another animal, whereas a poisonous animal can only deliver their toxin in a more passive manner (by being touched or eaten). A common example given to clarify this difference is that frogs are poisonous while snakes are venomous. It is also important to note that the affects from a venomous fish sting can often be relieved by immersing the wound in hot water (~105–115F) because these toxins are heat labile (meaning they can be destroyed or altered by heat).

1. Pufferfish (some species are also called toadfish) have been given the title ‘Most Poisonous Fish’ and have also been labeled the second most poisonous vertebrate in the world. The toxin responsible for ranking this fish so high in the “danger zone” is called tetrodotoxin. Tetrodotoxin is neurotoxic and inhibits neural transmission leading to weakness, paralysis, and even death at relatively low concentrations (~2mg). This toxin is found in the fish’s liver, ovaries, intestines and skin, leaving muscle tissue with relatively low and somewhat safe levels to eat. However, only highly trained and certified chefs are allowed to prepare this fish for consumption; a common practice in Japan where pufferfish are considered a delicacy.

Inflated Pufferfish (Source)

Pufferfish (Source )

2. Stonefish have usurped the title of ‘Most Venomous Fish’ in recent years. They often resemble encrusted stones (hence the name), blending into their natural environment with ease. They deliver their venom through a row of spines on their back that can be extended when threatened (or stepped on). Venom is involuntarily expelled when pressure is placed on the fish and the more pressure the more venom. They reside in the Indo-Pacific region and northern Australia. A sting from one of these fish can cause excruciating pain, rapid swelling, tissue death, muscle weakness, temporary paralysis, and in very rare cases death.

Stonefish (Source)

3. Lionfish were thought to be the most venomous fish until recent years when stonefish stole the title. These conspicuous fish have venomous dorsal, anal, and pelvic spines covered by a loose sheath that moves down and compresses venom glands when the spine punctures tissue. A sting from these fish can cause extreme pain, swelling, and in very severe cases, cardiovascular collapse. Most lionfish naturally reside in the Indo-Pacific but they have become an invasive species in recent years; most notably along the Atlantic coast of the United States where they are having a major impact on Atlantic coral-reef communities. Lionfish were likely introduced along the Atlantic coast through aquarium releases.

Lionfish (Source)

4. Stingrays are one of the most common groups of fish responsible for human envenomations; largely because many rays bury themselves on the seafloor where people unintentionally step on them. Stingray venom is generally cardiotoxic. The Bluespotted (native to the Indo-Pacific) and Southern (native to the southeastern US) stingrays are some of the most venomous of all stingrays. As a form of warning others, the Bluespotted stingray generally displays its bright blue colored spots as a warning to predators of its highly venomous sting.

Bluespotted stingray (Source)

5. Boxfish and trunkfish are closely related to pufferfish. While these fish are not nearly as poisonous as puffers, they do have an impressive way of defending themselves with poison. When threatened or stressed, they excrete a toxin from specialized skin cells into the water, poisoning marine life in their vicinity. The Hawaiian boxfish in particular excretes a toxin called ostracitoxin or pahutoxin that is known to breakdown or destroy red blood cells.

Boxfish (Source)

Some other venomous fish to check out are other scorpionfish (besides the stonefish and lionfish mentioned above), stargazers, which have two venomous spines in addition to organs near their eyes that cause electric shocks, and striped eel catfish.

Stargazer (Source)

If you know of any other venomous or poisonous fish not mentioned here or have experience with a species listed here please share your knowledge and experience below.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

References:

Auerbach PS. 2007. Marine envenomations. Adapted from the 5th edition of the textbook wilderness Medicine by Mosby-Elsevier.

Barss P. 1984. Wound necrosis caused by the venom of stingrays: pathological findings and surgical management. Med J Australia. 141: 854-855.

Boylan DB, Scheuer PJ. 1967. Pahutoxin: a fish poison. Science. 155:52-56.stingrays

Diaz JH. 2008. The evaluation, management, and prevention of stringray injuries in travelers.

Fenner PJ. 1998. Dangers in the Ocean: the traveler and marine envenomation. II. Marine Vertebrates. J Travel Med. 5:213-216.

Gwee MCE, Gopalakrishnakone P, Yuen R, Khoo HE, Low KSY. 1994. A review of stonefish venoms and toxins. Pharmacology and Therapeutics. 64:509-528.

Vetrano SJ, Lebowitz JB, Marcus S. 2002. Lionfish envenomation. The Journal of Emergency Medicine. 23:379-382.

Yang CC, Liao SC, Deng JF. 1996. Tetrodotoxin poisoning in Taiwan: an analysis of poison center data. Vet Hum Toxicol 38:282-286

http://ocean.nationalgeographic.com/ocean/photos/toxic-sea-creatures/

The Swimming Dead: Videos of Zombie Fish

2013-11-11T01:46:00.000-05:00

By Patrick Cooney

Like an underwater horror show, I filmed dead fish swimming amongst the living last week in a coastal river of western Washington. Or at least, the zombie fish looked like they were dead.

Nowhere is the "Circle of Life" more apparent than in a river during salmon spawning season. Years after leaving the comforts of freshwater as a juvenile fish for a massive journey to the ocean, adult salmon return to the exact same stretch of stream where they were born in order to spawn and die. That's right...one and done. Swimming back into freshwater is a one way ticket for salmon. Those fish lucky enough to make it to the spawning grounds are often on the edge of death, with flesh rotting from their bodies and bones protruding from fins.

In the process of swimming upriver, the radical transformations that salmon go through are nothing shy of remarkable. The jaws on males extend into large hooks, called kypes, with rows of sharp teeth to fight off other male challengers. Additionally, they change color from their oceanic shiny silver phase into deep reds or abstract streaks of blacks and purples, like an artist tripped and spilled their palette. Their flesh and muscle begin to soften and deteriorate as they jump waterfalls, fight river currents, and rub on rocks.

Salmon metamorphose as they migrate from saltwater into freshwater to spawn (Graphic: Cooney; Art: Tomelleri)

A portion of the migrating salmon will die along the route and will never make it to the spawning grounds. The bodies of the fallen end up littering the bottom of the river with dead carcasses that decompose their ocean derived nutrients and energy into the freshwater environment.

So, the next time you turn on the television or go to a movie and zombies are the central theme, you can share the truth with your friends. The living dead do exist, they have made a long journey across the ocean and up the river, and all they want to do is spawn.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog).

Song of Summers Past

2013-11-04T07:49:00.000-05:00

By Craig Springer, Guest Blogger

With this autumn’s leaves shedding, it gives one pause for all those summers that have slipped downstream. Sun-drenched memories are joyful like an Allman Brothers song.

Don’t fly mister bluebird, I’m just walking down the road. Early morning sunshine tells me all I need to know.

In memory, the buzz of bugs floated onto the flat and still waters, coming to my ears gentle and sporadic like soft waves splashing on a shoal. I creel-clerked at Caesars Creek Lake for the Ohio Division of Wildlife, checking angler harvest in what now seems like a lifetime ago. From the maples and hickories, and the box elders and dogwoods on shore, masses of cicadas droned incessantly. If sound had color, theirs would be a monochromatic shrill. It seemed like they were serious about their future—the bugs looked to mate, breed and die in a span of days. The summer air was memorable, stock still, and thick like an over-cooked pot of stew.

Fall Fishing (Source)

I killed the engine and walked forward. Standing on the gritty plywood bow of a short, well-used Jon boat, I watched the water surface turn into froth in a flurry of feeding fish. A school of white bass boiled the surface in a feeding frenzy, probably picking off luckless gizzard shad that would seize up at the sight of a mirror. This ball of white bass was easy pickings for a pair of anglers who I had approached. I stood by on my bow as an observer, as the two anglers participated in the food chain.

White bass have a sterling look about them, and a sterling quality on the end of a line. They will take a bright jig with iron tenacity, and make a run that pumps your forearm. A white bass is aptly named, for a fish pulled fresh from the water in summer sun looks intense, like polished chrome. The bluish-olive tinge, the color of good lake water on top of their back protects them from being seen by predators from above, like herons and ospreys and kingfishers. They transcend into broad silvery sides with tinges of gold on the bottom. Thin pencil-lead stripes, sometimes six of them, sometimes eight, run the lateral length. Below the lateral line, the stripes are faint, obscured. The whole fish in fresh condition looks like it is was cast in light steel, like a well-worn shotgun that needs re-blued.

White Bass, Morone chysops (NYDEC)

The white bass is to the striped bass what a rainbow trout is to a cutthroat—really close kin. Save for seasonal spring movements up the St. Lawrence, the two basses didn’t overlap much in nature. Some archaic thought professed that the white bass was a relic of a land-locked striped bass population, the artifact of being separated from a parent stock for an epic amount of time. The thought runs not too dissimilar to land-locked kokanee and its sea-run sister, sockeye salmon. The white bass co-occurs in some waters in its southern parts with other kin, the yellow bass and white perch. They’re all part of the marine grouper family of the Atlantic that includes the goliath.

Only a matter of miles away from where memory takes me, the glimmer of science shone on the white bass in 1818, just one of scores of plants and animals and fossils described for the first time by the picturesque Constantine Rafinesque. The Turkish-born, Kentucky professor of the natural sciences collected his white bass by hook-and-line at the falls of the Ohio near present-day Louisville.

They are called Morone chysops still to this day; there’s no known referent for the genus other than maybe “moron,” and with the recalcitrant Rafinesque, there might be something to that, he in his mind giving “acknowledgment” to a detractor. But that’s pure speculation on my part. The manic genius did have a large and hostile body of critics. The backend of the scientific name relates to the fish’s golden eye, as Rafinesque called his new fish, the “golden-eyed perch.” The cataract falls in the Ohio River where Rafinesque picked up his white bass are as extinct as the passenger pigeon, waylaid by locks and dams.

More recent vintage, the white bass has been planted in reservoirs across the country where the waters are clear and deep. The white bass didn’t get much attention as a game fish until dams on rivers proliferated in the U.S., post-1930s, and have since been stocked well outside their natural home waters.

And regarding home, it is astounding this trait of the human mind, that how the air decorated with a single sight, a sound or scent, can transcend years and miles and give you a pull to place.

Good old Sunday morning, bells are ringing everywhere. Going to Carolina, it won’t be long, and I’ll be there.

Yellow cottonwood leaves wafting to the forest floor at my New Mexico home in an instant send my mind sailing back to summers past. I’m on a Jon boat, the air is close and the heat intense, the bugs are buzzing and I’m watching a white bass boil on glassy water more than two decades ago.

Craig Springer is a fish biologist and the editor of Eddies magazine. He recently co-authored Spearfish National Fish Hatchery: Images of America in partnership with The Booth Society.

Find out more about US Fish and Wildlife Service Fisheries on Facebook. Be sure to "Like" The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

Scary stuff!

2013-10-28T06:43:00.000-04:00

by Brandon Peoples

It’s a quiet autumn night. The full moon barely penetrates the thick, low-hanging fog. An unsuspecting group is returning home from their evening activities. They’re in a dangerous area, but they know they’ll be safe if they stick together and move quickly. They’ve been lulled into a false sense of security …little do they know that just out of eyeshot, they’re being stalked by a killer.

The group finally makes it back to familiar territory. But as they slow down, the killer makes his move. Before they can make sense of the commotion, the killer is among them, striking with frightening speed. Amid the confusion, three comrades disappear instantly into darkness. But the killer miscalculates his attack on the fourth victim, who escapes injured. The group instantly realizes what is happening and is gone in a flash. The attack is over in a matter of seconds, and the killer finds himself alone in a sea of blood, dismembered bodies and scales.

As a member of Cyprinidae, the minnow family, this freaky-looking koi can emit schreckstoff when injured. Source.

Scales? Yes, scales—this is The Fisheries Blog, isn’t it! That scene wasn’t from a Halloween slasher flick…it’s played out by piscivorous fishes and their prey on a daily basis in a waterbody near you!

One reason the prey fish got away so easily—the focus of this week’s article—is a compound called schreckstoff. Many fish species excrete schreckstoff when they are injured. This alerts the rest of the school that danger is near. In a sense, fishes can actually smell fear.

Schreckstoff was first documented in 1938 by Austrian ethologist Dr. Karl von Frisch. Because he didn’t know the chemical makeup of the compound, he simply called it schreckstoff—German for “scary stuff”.

Chemical structure of chondroitin sulfate. Source.

Through a series of very clever experiments, a group of researchers from Singapore and Switzerland recently discovered that the active ingredient in schreckstoff is a molecule called glycosaminoglycan chondroitin. Click here to read up on their groundbreaking study, and check out this video of how fishes respond to shreckstoff in the lab.

For decades, many researchers believed that schreckstoff functioned only as an alarm cue. Within that context, they debated on whether its purpose was to prevent kin from suffering the same fate as the injured individual, or if it served to attract additional predators and confuse the original one, allowing the school time to escape.

It is now known that schreckstoff actually functions as an immune system response to parasites and pathogens such as molds, trematodes and solar radiation. Thus, schreckstoff probably functions only secondarily as a response to predators.

So next time you’re out on the water and see a group of predators decimating a bait ball, just think of all that liquid fear that’s floating around...happy Halloween!

Schreckstoff won't save these fish....

Paid to go fishing

2013-10-21T07:16:00.002-04:00

by Ed Kluender, Guest Blogger

It’s happened to most of us in fisheries field research, whether loading up the shock boat at a ramp, stopped at a gas station for tater wedges and bad coffee, or on the river when you run into someone who’s paying a guide to be there for nearly the same reason we’re there on the clock.

It starts with the initial, “What are you doing with all that weird gear?” Upon explanation is the inevitable, “Man, it must be nice to get paid to go fishing!”

I’ve seen a range of attitudes after this. Oddly enough, one of the more common responses is an uncomfortable mixture of resentment, cynicism, and anger that one could actually make a career of being on the water studying fish.

Humpback Chub are an endangered species native to the Grand Canyon. As a tourist, you can pay upwards of $1000 to visit this spot. As a fish biologist, you can make overtime pay there. Photo: Kristen Pearson

We often find ourselves audience to someone who is irate that the government (or, for the last 5 years, Obama) would stoop so low as to pay scientists to study and work to conserve the very resource the indignant angler is enjoying. When they find out that we’re out there after “trash” fish or anything other than trout or bass, it’s usually too late for a positive outcome to the conversation.

Sometimes, though, we’re lucky enough to be approached by someone who is genuinely interested in our work and open to a dockside education on habitat conservation and species diversity. And just often enough to keep our spirits up is the citizen who is so enthusiastic about it that they hang around to watch or even volunteer to help. Many of the people we meet in the field during work, regardless of their personal attitude towards us, have a general ignorance about what our work as fisheries field scientists actually is and why we do it.

It’s more likely to find a fisheries biologist pulling a seine through a muddy farm ditch with 95-degree water. Photo: Lindsey Lewis, US Fish and Wildlife Service.

At a recent departmental social, I introduced myself to the mostly wildlife (non-fish) group as a “professional fish bum.” It struck me as the most accurate title for myself now, as I’ve taken the last year and some to step back in my salary and career to work as a field and lab technician, mostly assisting graduate students with their studies. I’ve been all over Colorado and more, from the trickly plains streams full of cowpies to big desert gorges to alpine streams to tribal land in the Grand Canyon. It’s the kind of work that draws in most field biologists early and keeps us around later on. The work is exciting, rewarding in the short term, and keeps you traveling and working hard outside.

Most of us start out because we grew up fishing, hunting, camping, or otherwise getting an intimate practical education in nature. Taking a summer field job fresh out of high school is a good way to get to continue that uninterrupted. At a personal level, I think many of us fish squeezers are generally happier in our jobs than the average person since we’re not always working for the weekend. The line between our recreational time and work is fuzzier than for most careers. It’s not uncommon for us to finish the last site of the day and break out the rods and fish for a few extra hours before heading home or throw on the mask and snorkel and look for madtoms. Camping on wilderness gravel bars comes with the contract.

Some days, one of your most important research subjects gets stranded and dies and you spend the night doing a necropsy on a giant rotting fish. Photo: Clint Johnson

Somewhere along the line, though, we start to understand and care about the resources, the habitat, and the species. Maybe it’s in school where a professor points out how rapidly fish populations worldwide are declining. Maybe it’s witnessing the aftermath of an irresponsibly managed bowfishing tournament or seeing our favorite smallmouth stream being gradually silted in by a gravel mine. At some point, we realize that to keep our streams and lakes healthy, it takes not just knowledge, but the special kind of love that we have to protect our water for the rest of the world.

Anyone has the capacity to learn and understand why humans and all other animals depend on rivers and streams. It’s a different type that takes on a low-paying jobs and the Sisyphean career of trying to protect fish and their habitats for their own sake as well as ours.

Every now and then, we really do get paid to go fishing. Photo by Brian Avila and Colorado Parks and Wildlife

So to those of you we meet at the river that encourage us and want to learn, we do it for you. And to those of you who think government money would be better spent putting more trout in the river, we do it for you too. On the days you don’t see us, we may be slogging around in wastewater effluent at your local treatment plant or doing necropsies on a thousand rotten shad that inexplicably died yesterday. We may be on all fours in a cottonmouth-infested farm ditch getting rid of invasive species that threaten native sunfish or pulling in hoop nets full of irate snapping turtles.

On some days, it is getting paid to run whitewater and go fishing. But every day, it’s work that we chose because we have the desire to take care of a resource that’s precious to everyone.

Ed Kluender (kluender@rams.colostate.edu) is a research associate in the USGS Cooperative Fish and Wildlife Research Unit at Colorado State University.

Be sure to like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to to have us email you our weekly article. right of this page to have us email you our weekly article.

When the quick cure causes long-term danger: Who knew antibiotics could be such a problem?

2013-10-14T03:05:00.001-04:00

by Dr. Dana Sackett

Whether for an ear infection or something more serious, chances are we have all had to take antibiotics at one point in our lives. Despite this regular use of antibiotics, few people know where they come from or that our overuse of these drugs are causing some serious problems in our aquatic environment.

Antibiotics come from the chemical warfare that occurs between microscopic organisms that have developed natural defenses to protect themselves from other microscopic organisms. For example, penicillin, one of the earliest and most widely used antibiotics, was discovered when Sir Alexander Fleming observed that mold (Penicillium notatum) produced a natural substance that destroyed bacteria (Staphylococcus aureus) in 1928. Since this discovery, hundreds of these bacteria-killing substances have been discovered and many are synthesized and mass produced as our own personal weapon against disease causing bacteria.

(Source)

The problem with this widespread use is that a large portion of the antibiotics consumed by people, or those used in fish farming and agriculture, make their way into our lakes, rivers, and oceans. At first glance, this may not seem like a big deal; the more antibiotics there are, the more the protection from those disease causing bacteria, right? Not exactly.

Not all bacteria are bad. Bacteria play a crucial role in the breakdown of waste when water is treated in our sewer system. Antibiotics can prevent useful bacteria from “cleaning” wastewater properly before it is released into the environment. For example, nitrification, a process which requires bacteria, is an important step in wastewater purification that eliminates toxic ammonia. The presence of antibiotics in wastewater can inhibit this process and may lead to the accumulation and release of a toxic form of nitrogen into the aquatic environment, potentially poisoning local aquatic species.

Wastewater treatment plants provide the perfect environment for antibiotic-resistant "superbugs" to be created and eventually released into streams and lakes. (Credit: Image courtesy of University of Michigan).

Unpurified sewage water isn’t the only problem for aquatic species. Antibiotics can also cause collateral damage by killing microorganisms other than bacteria. Algae, particularly bluegreen algae, are frequently killed when antibiotics are released into the environment. Because algae often make-up the base of the food chain, even slight decreases in algae may affect aquatic ecosystems.

Another major concern with antibiotics in our water is resistance. Because many bacteria multiply rapidly (many can double their numbers every 20–30 minutes), continuous exposure to low levels of antibiotics can allow bacteria with a mutation to resist or survive the antibiotic to grow quickly and even share those resistant genes with other bacteria.

Commercial antibiotics are easily available for aquariums (Source)

As a result, bacteria resistant to antibiotics have been seen in the environment with the potential to harm aquatic species and people. In particular, wastewater treatment plants and fish farming (aquaculture, mariculture) have been associated with the development of antibiotic resistance. Fish farming, where fish are frequently treated with antibiotics and kept enclosed with water that circulates to and from a local water source (e.g. river, ocean), is a specific concern because antibiotics can enter the environment directly without undergoing any kind of purification process.

A new system for aquaculture where water is not circulated to and from a local water source (traditional approach), but operates without any water exchange from the environment, preventing the release of antibiotics into local waterbodies. (Source)

With an estimated 100,000 to 200,000 tons of antibiotics being used each year to combat disease in people, livestock, pets, and fish, how do we prevent these chemicals from killing those good microorganisms necessary to ecosystem function or creating "superbugs" that cannot be treated with antibiotics? The answer is to use antibiotics sparingly (not insisting on antibiotics for ailments they don’t treat, such as a cold, and not flushing unused drugs down the toilet).

(Source)

Fewer antibiotics in the natural environment ensures minimal collateral effects on other species and fewer opportunities for bacteria to develop resistance to the currently used antibiotics. With the prevalence of resistant bacteria spreading, scientists are searching for new antibiotics to combat the "superbugs", but with very few new antibiotics being discovered and produced since the 1970’s, the race is on to find new drugs.

Be sure to Like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

References and more:
http://phys.org/news/2012-11-antimicrobial-resistance-fish-pathogenic-bacteria.html

http://www.sciencedaily.com/releases/2009/05/090512193238.htm

http://www.earthtimes.org/going-green/hope-aquaculture-eco-clean-fish-farms/1188/

http://www.bbc.co.uk/news/health-21739378

http://www.phdcomics.com/comics/archive.php?comicid=1635

Kummerer K (2009) Antibiotics in the environment – A review – Part I. Chemosphere 75:417-434.

Kummerer K (2009) Antibiotics in the environment – A review – Part II. Chemosphere 75:435-441.

Tacao M, Correia A, Henriques I (2012) Resistance to broad-spectrum antibiotics in aquatic systems: anthropogenic activities modulate the dissemination of blaCTX-M-Like genes. Appl Environ Microbiol 78:4134.

The Four "Fs" of Fish

2013-10-07T00:45:00.000-04:00

We recently had the distinct pleasure of meeting Abby Lynch, a fisheries research scientist with Michigan State University. Please read her great story below and look for more from her on The Fisheries Blog in the coming months.

Some time ago, on my way back home after an international trip, I was asked by the immigrations officer at passport control what my profession was.

I said, “I am a fisheries scientist.”

“Huh,” he said. “I’ve never heard that one before. So, you work with fish?”

“Yes; I study how environmental factors and fishing pressure influence fish populations.”

I suppose my answer was sufficient for him; he just stamped my passport and moved on to the next person in line. But, reflecting on the event, it was a missed opportunity for me to explain why fish are important to him, even if he had never thought about fish before. Fish are valuable for a lot of reasons; but, in the 30 seconds I spent with that immigrations officer, I could have boiled it down to the four “Fs” of fish: food, finances, fun, and function.

Food: Three billion people (> 40% of global population) depend directly upon fish as an important source of nutrition;
Finances: 540 million people (8% of global population) depend upon fishery industries for livelihood and income;
Fun: In the U.S. alone, anglers spend over $40 billion in support of fishing activities annually; and,
Function: Fish comprise more than half of all vertebrate animal species and occupy all major aquatic habitats.

Food

How's the fish?
Fish meal is often used in feed for other livestock.
So, eating that turkey leg is possible thanks to fish.

Capture fisheries are the last large-scale wild food resource in the world and aquaculture is a quickly growing sector. Both provide essential protein and nutrients to many across the globe. According to the Food and Agriculture Organization of the United Nations (FAO), fish directly provide more than 1.5 billion people with almost 20% of their animal protein and another 3.0 billion with at least 15%. Combined, that means fish are directly feeding more than 40% of the world’s human population. Fish are also an important indirect source of protein for many others who generally do not realize it. Fish meal and oil is often an important component of feed for livestock. So, choosing between chicken and fish as meal options may, in fact, be choosing between fish…and reprocessed fish.

Finances
FAO estimates that global first-sale value of capture fisheries and aquaculture is $192.3 billion, annually. That’s the equivalent of one-seventh of the U.S. Gross Domestic Product. And, it’s only the first-sale value of the fish – only the first step in a potentially long supply chain. In terms of jobs, 44.9 million people are employed by fisheries or aquaculture systems, according to FAO. All of these FAO estimates are likely to be gross underestimates because of difficulties with reporting in many countries and many fisheries. Even still, at minimum, fisheries employ more than 20 times more people than Walmart, the world’s largest private employer.

Fun
Fish are also fun. From watching fish in the dentist office waiting room to fish on the end of a fly rod, people enjoy many fishy hobbies. While these personal experiences are extremely important to the people who have them, they can be appreciated even by folks that don’t in terms of money. The U.S. Fish & Wildlife Service estimates that Americans spend $41.8 billion on angling activities alone. That’s a massive industry and the estimate doesn't even include others involving fish, such as SCUBA diving and the aquarium trade.

Function
Fish are the most diverse group of vertebrates on earth – almost 28,000 species -- more than half of all living vertebrate species. They also inhabit almost every aquatic ecosystem on the planet. They are often equated to aquatic “canaries in a coal mine” because they are indicators of ecosystem health and, in some cases, a litmus test for potential impacts of environmental change on humans.

So, the next time I go through passport control, I might meet an immigrations officer who eats fish or is a recreational angler. For him or her, the importance of fish will be an easy sell. But, if I meet another officer that doesn’t have any direct contact with fish, I’ll be ready with a better answer -- the four Fs of fish: food, finances, fun, and function!

By Abby Lynch

For more information, please refer to:
Lynch, A. J. and W. W. Taylor 2013. The Four Fs of Fish: Communicating the Public Value of Fish and Fisheries. Fisheries 38(1): 43-33.

Be sure to Like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

The Other Side of Fall Leaves

2013-09-30T01:52:00.000-04:00

By Steve Midway

Around this time of year throughout much of the northern hemisphere, we take pause to notice the beautiful spectrum of colors presented in fall foliage. Have you ever wondered what happens to all of those leaves, where they go, and what types of animals may benefit from this fall bounty?

Leaves change from green to yellow to red before being deposited
in rivers and fueling a long-term food chain. (Source)

As a quick refresher, throughout the fall the green chlorophyll that photosynthesizes energy for trees all spring and summer is being replaced by other pigments in the leaves in a predictable sequence. The yellow pigments appear first, as the yellow compounds are actually present in the leaves along with the green chlorophyll all year long—just not enough to overcome the green pigments. Next come the orange, then the red pigments, which, unlike the yellow, are actually created in the fall. Rainfall, temperature, sunlight, and a host of other factors influence the timing of fall leaf color change, but ultimately photoperiod (hours of sunlight in the day) is the main driver causing leaves to change and fall regardless of other conditions.

Not all leaves change at once, but rather, they
change over a period of weeks. (Source)

Okay, now that we are all up to speed on leaf colors, what does all this have to do with fish? Actually, a lot. Following the dark red colors, the trees no longer need the leaves, so they are released. As useless as these leaves may seem to the tree, they are still chock-full of organic matter and other potential foodstuffs for others to enjoy! When they fall in our yards, we rake them and collect them, but when they fall in or near a stream, they represent a huge addition of nutrients to the system.

Fallen leaves entering flowing waters represent
the start of a stream-wide feast. (Source)

For tree-lined waterways, the annual leaf-dump initiates a chain reaction of feeding that helps sustain all levels of biological diversity and abundance through the tough winter months. When leaves first enter the water, they leach out dissolved organic matter, DOM. This is the brown stuff that stains puddles the color of tea, or that brown leaf-stamp that imprints on your car (for those of us who forget to wash our cars in the fall). The DOM is mainly available to bacteria and fungi, but this is only the beginning of the process; the ecosystem-wide meal is still to come.

One of the best ways to see the fall color is along a stream or river. (Levan)

Both the bacteria and fungi and the now-decomposing leaves serve as a major food source for the aquatic invertebrate community. This can include a wide range of species—for example many anglers will be familiar with stonefiles and caddisflies. As the leaves continue to break down, both shredder and collector insects further process the leaves for food and shelter. In turn, these aquatic insects are the main food source for a healthy fish population.

Stream invertebrates like these caddisfly larvae are happy to shred up
decomposing leaves and make them into homes. (Source)

You don't have to look far to realize that invertebrate diversity and abundance is a near-critical requirement for stream fish. Of course some fish eat other fish, but at the lowest level, fish need a healthy supply of aquatic insects. And this food supply is largely dictated by the quantity and quality of the annual leaf fall. So as you take a moment to enjoy this year's autumn foliage, consider the importance of the leaves not only while they are on the tree, but also their importance after they fall, and all the hungry little fish that are eagerly staring up into the orange and red sky along with you.

After months of leaf processing, the improved health of the
aquatic insect population directly benefits fish. (Source)

Note: Numerous studies have confirmed the importance of leaf matter to stream ecosystems. For those interested in more information, the links below represent a sample of some of these studies.

Wallace et al.—declines in abundance and biomass of invertebrates.

Graca—a review of invertebrates and leaf litter.

Woodward et al.—using leaf litter to evaluate stream health.

Be sure to Like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

Check out the video below, where some fish, like grass carp that are native to Asia, actually eat the leaves as they fall onto the water:

The Role of Social Media in Fisheries Science

2013-09-23T00:53:00.001-04:00

Brandon Peoples (@FisheriesBlog)

Let me tell you a little secret: I don’t have a smart phone or keep up with Game of Thrones. As a matter of fact, for a younger guy, I’m pretty old-school. Accordingly, I was a huge skeptic of online social media…but I’ve always seen the value of non-technical communication in science. In fact, some people (e.g. M*A*S*H's Alan Alda) would even argue that communicating with the public is a scientist's foremost responsibility.

With success stories like Deep Sea News, Science Sushi, Southern Fried Science, and The Fisheries Blog, it’s hard to ignore the value of social media in fisheries science. Even chapters of the American Fisheries Society are getting in on the action. Hell, even this fish found value in the use of a smart phone!

Despite my initial skepticism, I recently began to understand the necessity to use social media or run the risk of quickly losing scientific relevancy. That is why I started writing for The Fisheries Blog.

Melissa Marshall asks scientists to talk nerdy to her!

Plenty of others are beginning to agree. Many of them recently convened in Little Rock at the 143rd Annual AFS Meeting in a symposium dedicated to sharing ideas about using social media to better communicate fisheries science. The symposium was hosted by the Fisheries Information and Technology Section of AFS (FITS).

Instead of summarizing each talk myself, I asked several speakers to give us their “take-home” message…

Anne McElhatton (@bcsanswers), who writes the blog Beach Chair Scientist, outlined the different platforms fisheries scientists can use to communicate more effectively: “...A general rule of thumb is to ask “Is this essential to the core message?” Blogging can be an effective way to share additional information to those interested in further details.”

Julie Claussen of the Illinois Natural History Survey convinced us that Twitter is an incredibly useful source for job seekers in fisheries. Julie (@FishConserve) encouraged us to “Get out of your science comfort zone and broaden your community using Twitter. As in any community, you can stand back and listen, or jump right in and interact... and you might just find a job!”

The Fisheries Blog's very own Patrick Cooney (@FisheriesBlog) compared readership of research published strictly in traditional scientific journals versus those promoted through online media: “Publishing is only the first step in properly disseminating scientific research. Recent analytics show that without using social media to share your work, you and your co-authors will most likely be the only people that end up reading about your hard work.”

The Fisheries Blog, AFS-FITS and others kept members who couldn't attend the conference updated with their Twitter and Facebook accounts.

Julie Defilippi (@DefilippiJulie), a session moderator presented on a recent survey of social media use in AFS. The survey was designed to “…help AFS parent society, sections, divisions, chapters and individuals communicate better.” The results of the survey are soon-to-be published in Fisheries magazine.

State management agencies also had a nice showing. Tom Lang of Texas Parks and Wildlife spoke about how TPWD uses its Facebook page as a fisheries management tool. According to Tom, “When it comes to fisheries management, leaving people out is like playing a football game and leaving your defense in the locker room…Social media is how the public is communicating and if we don't embrace this societal change then we are greatly risking the erosion of our own social relevance.”

Thom Litts of the Georgia DNR gave a nicely quantitative presentation on the effectiveness of GDNR’s social media communication strategies. GDNR uses Facebook, Twitter, Blogs, and automated license renewal notices. Thom studied the influence of these communications on angler license buying behavior. The presentation described some of the methods and limitations encountered while trying to answer this question.

So all you scientists out there, I understand your hesitation to jump into the mix of social media. But take it from an old-school guy like me who has seen the results: there is a huge return in scientific relevancy with a very small investment in the use of social media. As for all you non-scientists out there...be ready for us to talk nerdy to you!

Check out 2 recent articles on social media in fisheries science in the August 2013 issue of Fisheries.

Be sure to "Like" The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

Topless Mermaid Protestor Misunderstands Scientists

2013-09-16T09:22:00.000-04:00

By Patrick Cooney

Mermaids misunderstand scientists that are presenting in hotel behind (source).

In the 1980s box office hit titled Splash, a scientist nearly goes mad while attempting to advance his cause by exploiting a mermaid. As if making a reference to the movie, but in a complete reversal of roles, a topless mermaid took to
the streets of Little Rock, Arkansas last week to advance her cause by exploiting scientists.

Source

The 143rd Annual Meeting of the American Fisheries Society (AFS) convened last week in Little Rock. More than a thousand scientists from around the globe shared more than 700 presentations about ongoing aquatic science projects. Scientists in attendance hailed from Brazil, Canada, England, Ireland, Japan, Mexico, Puerto Rico, Scotland, South Africa, South Korea, Taiwan, and from all 50 of the United States of America.

People for the Ethical Treatment of Animals (PETA) caught wind of the international conference, and in a rush to judgment they set up a small protest of the event to promote the agenda of their organization. PETA often uses dramatic events to promote their message, but the protest was most likely a misunderstanding rather than a disapproval of what AFS scientists represent.

The American Fisheries Society is the oldest and largest professional society for fisheries scientists in the world, and is comprised of over 9,000 members from government agencies, academic institutes, and private industries. AFS scientists advance sound science and disseminate science-based fisheries information for the global protection, conservation, and sustainability of fisheries resources and aquatic ecosystems. AFS and its members support six professional peer-reviewed journals, and hold continuing education classes to promote up-to-date techniques and analyses in the fisheries science profession.

With global fish stocks under immense fishing pressure, perhaps viral protests like the one used by PETA are a way to attract immediate attention. However, considering that AFS has 143 years of experience, maybe the protestors should have come inside to learn how AFS is successfully using real science to support the conservation and sustainability of fish and habitat rather than simply protesting on a sidewalk for a few minutes posing as mythical mermaids.

Be sure to Like The Fisheries Blog on Facebook and follow us on Twitter (@FisheriesBlog). Also, be sure to enter your email at the top right of this page to have us email you our weekly article.

Source

Is the Kiddie Pool Safe? Pollution in Coastal Fish Nurseries Affects Offshore Populations

2013-09-09T09:42:00.000-04:00

By Tobey Curtis

Do you take your young kids to a daycare or nursery? These are places where we expect our children to be, at minimum, safe and nurtured. Nurseries help ensure survival and growth to a well-adjusted adulthood. It turns out that many ocean-going fish use the same strategy for their young.

It has long been recognized that numerous offshore fish, including important recreational and commercial species like bluefish, flounders, snappers, and sharks, are dependent on shallow coastal bays, lagoons, and estuaries as juveniles. These shallow, protected waters offer habitats like seagrass beds, mangroves, or marshes that can shield young fish from predators and provide abundant food. Then, as fish eventually outgrow their shallow nursery habitats, they transition to offshore areas where they mix with the adult population.

Shallow fish nursery areas, like this mangrove habitat, provide food and protection for young fish. Photo: Brian Skerry.

This is why it is so troubling to hear about ongoing habitat destruction and degradation in coastal zones. Any habitat alterations that reduce the abundance of prey or take away shelter from potential predators can reduce the “nursery effect,” and may eventually reduce adult fish populations (i.e., through loss of recruits). Nearshore habitat degradation, therefore, can directly affect the offshore environment.

A recent example of the consequences of pollution and habitat degradation in a nursery area is the Indian River Lagoon (IRL) along Florida’s Atlantic coast. The IRL is considered the most biologically diverse estuary in North America, and is home to over 400 species of fish, many of which use the lagoon as a juvenile nursery. The lagoon is world famous for its sport fisheries for snook, red drum, spotted sea trout, and tarpon, and is a well-studied nursery area for bull sharks.

Over the years, the IRL shoreline has experienced obvious habitat alterations including construction and urbanization, dredging, altered water flows, and removal of marshes, seagrass, and mangroves. These alone have reduced suitable nursery habitat. But there are also less obvious, and more insidious, sources of degradation that have come to a head in recent years. Due to years of population growth in the region, but no real upgrades in wastewater management and sewerage, the lagoon has experienced dramatic declines in water quality. This has, in turn, led to a variety of negative impacts on the IRL's fish and wildlife.

Tracking positions of juvenile bull sharks in the Indian River Lagoon nursery area. These young sharks at times seem to prefer altered habitats like dredged boat marinas, which exposes them to high levels of pollution. (From Curtis et al. (2013), Marine and Coastal Fisheries)

The growing additions of nutrients like nitrogen and phosphorus from fertilizers and stormwater runoff contributed to more frequent harmful algal blooms (e.g., toxic "red" and "brown tides") which directly killed thousands of fish. In 2011, there was an unprecedented "superbloom" of algae which choked the oxygen out of the lagoon, cut off sunlight, and killed tens of thousands of acres of productive seagrass beds. Fish kills, and the deaths of hundreds of dolphins, manatees, and birds have become common in the last year. Even though it is often difficult to identify the direct causes of these deaths, years of declining water quality set the stage for these environmental catastrophes.

Seagrass coverage in the IRL has crashed in the last few years, but we don't yet know what the full consequences may be for local fish populations. Source: St. Johns River Water Management District (sjrwmd.com)

In addition to nutrient loading, IRL fish have been documented to carry high loads of toxic contaminants like mercury, pesticides, PCBs, and flame retardant chemicals. They are also exposed to common pharmaceuticals and personal care products (e.g., prescription and non-prescription drugs, perfumes, soaps, cosmetics), which are not typically extracted by water treatment facilities. We don't yet know if these contaminants are negatively affecting the health of these animals, but they could collectively reduce the survival rates of juvenile fish.

Source: FloridaToday.com

Many people believe that overfishing is still the primary threat to the sustainability of valuable fish stocks. But we can’t rebuild depleted adult fish populations without a healthy crop of juveniles. For fish dependent upon coastal nursery areas, pollution and habitat destruction may be surpassing the negative effects of fishing in some places. These impacts need more research attention. Effective fisheries management must consider human-induced impacts on essential fish habitat, especially nursery areas.

Habitat restoration, upgraded wastewater management practices, and mitigation of these various types of degradation are needed to help regions like the IRL recover. The IRL has an estimated annual value of over $3.7 billion (with a “B”) to the regional economy. Therefore, reducing our impacts on coastal habitats is not just about our appeasing our environmental conscience and rebuilding fisheries – it’s about dollars and cents, and sustaining entire coastal economies. And now it’s probably going to be much more expensive to repair the catastrophic damage done, than it would have been to take preventative measures a few years ago.

Tobey is a PhD Candidate, School for Marine Science and Technology, University of Massachusetts-Dartmouth

Follow Tobey on Twitter @Mojoshark

References

Beck, MW, et al. 2001. The identification, conservation, and management of estuarine and marine nurseries for fish and invertebrates. BioScience 51:633-641.

Curtis, TH, et al. 2013. Use of human-altered habitats by bull sharks in a Florida nursery area. Marine and Coastal Fisheries 5:28-38.

Kennish, MJ. 2002. Environmental threats and environmental future of estuaries. Environmental Conservation 29(1):78-107.

Lotze, HK, et al. 2006. Depletion, degradation, and recover potential of estuaries and coastal seas. Science 312:1806-1809.

St. Johns River Water Management District: The Indian River Lagoon: An estuary in distress.

Come see our presentation

2013-09-07T12:48:00.002-04:00

If you are going to be at the American Fisheries Society meeting this coming week in Little Rock Arkansas, be sure to see our presentation:
Communicating Fisheries Science to an Internet Audience
Tuesday morning (10:40am, 09/10/2013)
Fulton Room

How Obama's fish made me question my view of "species"

2013-09-02T07:48:00.000-04:00

By
Brandon Peoples

Just what "is" a fish species? Etheostoma clinton may say, "...it depends on your definition of 'is'."

Last year, researchers Steve Layman and Richard Mayden discovered five new species of darter—tiny colorful fishes in the perch family. They named the new species after "environmentally-minded" politicians, most notably Barack Obama (Teddy Roosevelt and Al Gore also made the list). These “new” species had been hiding from us in plain sight—the southeastern US.

Five new species of Etheostoma were recently described in the southeastern US. Photos by J. Tomelleri. Source.

Wait…how did five unknown fish species go undetected for so long right under our noses?

Originally, all five species were thought to be one and the same—the speckled darter E. stigmaeum. This “species complex” represents a case of cryptic diversity.

Traditionally, taxonomists relied solely on morpho-meristics—comparative ratios or counts of body parts—to distinguish species from one another. But with the molecular tools available to modern ichthyologists, variation among species can be examined in ways not possible before the mid-1970s. So basically, Layman and Mayden found genetic variation within the speckled darter complex similar to what is typically seen among described species. That, accompanied with noticeable coloration differences in breeding males, warranted their consideration as new species. Black bass in the southeastern US are currently being studied in a similar way.

Widely distributed species like the speckled darter are often "split" into separate species. Source

In the past three decades, scores of new species have been described through this process of “splitting” species from one another.

Not all biologists agree with every new species designation. Some may argue that distinct morphological differences are only visible during the breeding season. Others contend that because the new species seldom co-occur, the primary thing that makes them distinguishable (other than genetics) is the river in which they were captured…so what if they became introduced in other systems?

These differences have divided some biologists into two camps: splitters (those that split into different species) and lumpers (those that lump all into one species).

In reality, whether or not you drink the proverbial splitting Kool Aid will most likely depend on which species concept (how a species is defined) you identify with. Three main concepts are described below…which one makes the most sense to you?

Biological species concept: Possibly the most widely taught, this concept stresses the importance of separate breeding populations. Basically, if the groups do not interbreed with one another, they are separate species.

But if geographic isolation caused the speciation, then how could they ever have the chance to naturally interbreed?

Ecological species concept: This concept focuses on the species’ niche or role in the environment. Species are delineated based on their function. Species are further identified by whether or not they would compete for resources (since similar species require similar resources).

But what if they use different resources throughout their geographic range or lifespan?

Genetic species concept: Under this concept, species are organisms that share the same evolutionary fate through time. For headwater fishes, this is often through isolation.

But how do you convince lawmakers all these very similar species deserve unique protection?

This is more than a matter of systematics—defining species can clearly have significant regulatory impact (think of the Endangered Species Act). Throw in classifications of subspecies and stocks, and things can get confusing.

So before you go pick sides, your best bet is to educate yourself…how would you define a “species”?

The Fate of Released Aquarium Fish

2013-08-26T08:29:00.000-04:00

It's been estimated that close to 10% of US households have aquariums. And why not—aquariums are an inexpensive and interactive way to observe a variety of fish, often with minimal upkeep for a pet. Yet despite the ease with which you can purchase and possess a wide range of fish species, there is a growing list of ecological concerns that accompany the aquarium industry.

Home aquariums can range from the classic fish bowl, to just about anything. (L, R)

Earlier this month in Science, Magalhães and Vitule reminded us that most introductions from aquaria come from (1) intentional release, (2) unintentional release (often at breeding facilities), and (3) discarding of unnoticed juveniles. Because intentional release is likely the most common type of release, I would like to review some of the scenarios we have seen play out following release of aquarium pets.

Lake Tahoe, on the border of California and Nevada, is one place that is no stranger to introduced species. Recent estimates place over 50% of the Lake's freshwater fish as introduced species. Obviously, some of these species were put there on purpose—like many trout species—to increase angling opportunities. However, some goldfish in Lake Tahoe have acclimated well, and are weighing in at several pounds. Biologists are concerned that as the Lake warms with the climate, warmwater goldfish will have an increasing advantage over native species.

Large goldfish sampled in Lake Tahoe. (California Department of Fish and Wildlife)

California Department of Fish and Wildlife

On the east coast of the US, many people are familiar with the growing range and increasing density of the Indo-Pacific lionfish. The source of the introduction(s) of lionfish is not known, but some attribute the introduction to ballast water from cargo ships. Others claim that lionfish were introduced when Hurricane Andrew (1992) damaged a beach-side aquarium, and subsequently released fish into the nearby water. Although both of these introductions could be considered unintentional, others suspect that lionfish are continually introduced when they outgrow a home aquarium. And based on the popularity of aquariums and lionfish in Florida, these intentional releases are likely. What is known about lionfish in the Atlantic is that they lack a natural predator and that their establishment and successful reproduction is negatively impacting native species. In fact, lionfish are doing so well in the Atlantic, they have become overweight.

Lionfish are established throughout the southeast US Atlantic. (Source)

Of course, aquarium releases of invertebrates and even algae—not just fish—can cause extensive ecosystem damage. A variery of snails and algae have similarly negative stories surrounding their release into non-native waters. Many developing countries now have regulations concerning importation of aquarium species, but of course, many countries do not have regulations and illegal importing goes on everywhere.

We're not against aquariums by any means—we just want to help people become responsible aquarium owners, which includes preventing your investment from invading and degrading a nearby ecosystem. And if you still want to flush or dump your goldfish, please consider following some of the American Veterinary Medial Association's guidelines on euthanizing your beloved pet (page 67 for fish). (If you have a native fish aquarium, good for you, but due to often unnoticed diseases, please don't release your fish back into the wild!)

Steve Midway

Additional reading:
Lake Tahoe Goldfish
Lionfish Invasion
Lionfish: Worst Case Scenario
Review of Aquarium Releases

Finding Nemo lied to your kids, and they will do it again in the sequel: Finding Dory!

2013-08-19T01:12:00.000-04:00

By Patrick Cooney

The Disney film, Finding Nemo, lied to your kids! Disney would simply argue that they altered reality to create a more entertaining storyline, but read below for the true story, and you tell me which you think is a more entertaining.

Disney forced them to hide the truth!

How Finding Nemo started:

Father and mother clownfish are tending to their clutch of eggs at their sea anemone when the mother is eaten by a barracuda. Nemo is the only surviving egg and he grows up in his father’s anemone before getting lost on a crazy adventure!

Video of the opening scenes:

How Finding Nemo should have started if it were biologically accurate:

Father and mother clownfish are tending to their clutch of eggs at their sea anemone when the mother is eaten by a barracuda. Nemo hatches as an undifferentiated hermaphrodite (as all clownfish are born) while his father transforms into a female now that his female mate is dead. Since Nemo is the only other clownfish around, he becomes a male and mates with his father (who is now a female). Should his father die, Nemo would change into a female and mate with another male. Although a much different storyline, it still sounds like a crazy adventure!

Video of the truth:

As you can see, the first minute of Finding Nemo, outside of the talking fish part, is the only biologically accurate part of the movie. Considering that they demonstrate reproduction and the killing of the mother in the first minute of the movie, how did they decide that a natural sex change is outside the bubble of viewable material?

Fish reproduction is complicated, and it is especially complicated in cases like the clownfish where species are sequential hermaphrodites. These fish are born as hermaphrodites that develop as one gender before changing to the other gender at some point in their life.

Unlike clownfish that start life as males and transform into females, there are other species, like the California Sheephead, that start as females and transform into males. These opposing forms of sequential hermaphrodites are called protandrous hermaphrodites for male to female changing species, and protogynous hermaphrodites for those that change from female to male.

The truth!

A sequential hermaphrodite life history strategy can be extremely detrimental if harvest of fish is allowed prior to male or female reproductive sizes. Should all males be harvested before turning into females at a certain size (or vice versa), a rapid decline would occur in the population. Understanding the triggers and sizes at which fish shift from one sex to the other greatly enhances the ability of fisheries managers to set proper length limits for long term fish population health.

More lies and deception?

In the end, the storyline for Finding Nemo was obviously entertaining for children, but as a fisheries scientist, I must admit, I find the biologically accurate storyline a bit more entertaining. With the announcement of a sequel called ‘Finding Dory’ coming in 2015, Disney still has a chance to redeem themselves, but I am not keeping my small 'lucky' fin crossed. Which storyline do you think Disney should show in the sequel?

Be sure to check out The Fisheries Blog on Facebook and Twitter (@FisheriesBlog). If you want to receive our weekly blog through email, leave your email address in the open space at the top right of the page (scroll up!). Also, check out an article we wrote a year and a half ago about how birth control in the water is causing fish to display both male and female gonads at the same time.

(Source)

Scientists group fishes to improve prediction

2013-08-12T07:08:00.001-04:00

Brandon Peoples

Most scientists share the gripping compulsion to place things into tidy categories. Fish ecologists are no exception.

Why group?

Grouping species helps improve our understanding and management of aquatic ecosystems. Because local fish diversity can be quite high, predicting responses of individual species to environmental change or nonnative introductions can be difficult. Grouping fishes based on biological or ecological similarities can help reduce that complexity because species in the same group often respond similarly to same threats.

Didn’t we already have groups?

By the time we finish elementary school, we’re all familiar with the hierarchical Linnaean classification system that groups organisms by their common ancestry. Of course, this system is one of the greatest contributions to the natural sciences, and is the basis for phylogenetic analysis.

However, closely-related species often perform starkly different ecological functions. For example, darters are much more closely related to walleye (they’re in the same family, Percidae) than they are to sculpins. Yet, darters eat, behave and function much more similarly to sculpins than to walleye.

Thus, in ecological analyses, phylogenetic groupings may not always be as effective as other types of groups.

Redfin darter (left) and banded sculpin (right) are small benthic insectivores that inhabit riffle habitats; walleye (center) are large pelagic predators. Source

What types of groups?

Fishes are often grouped according to guilds—species that exploit the same resources typically in similar ways. Guilds can be based on any ecological requirement (some of these include flow, habitat type, etc…). The two most commonly applied guilds are trophic (feeding) and reproductive.

Trophic. Trophic guilds are classified by what fishes eat and are subdivided by how they eat it (modes of feeding). A well-accepted classification system* of freshwater fishes recognizes five trophic guilds and 26 feeding modes. For example, there are 10 different feeding modes that invertivores use. A few of these include surface drift feeding, grazing and digging.

Carmine shiners are drift-feeding insectivores, and can be affected by riparian deforestation. Source

Reproductive. Reproductive guilds are firstly classified by what is done after eggs are laid—they are either guarded, unguarded, or born on/inside the fish. Within this scheme, classifications are subdivided based on the substrate needed for spawning**. A few examples include lithophils (requiring gravel), psammophils (requiring sand), and speleophils (requiring cavities).

How do fish ecologists use groups?

Human impacts. Groupings have greatly improved our understanding of the impacts of human development on fishes. In fact, groupings are the basis of community-level bioassessment. For instance, abundances of lithophilic fishes predictably decrease with increasing sedimentation from human development.

Simple lithophils like this blacktip jumprock are vulnerable to sedimentation. Photo by Brandon Peoples.

Indirect effects. Groupings help us to conceptually simplify food webs to improve fisheries management. Many fisheries-related problems, especially in smaller systems, are related to unbalanced food webs. Understanding which group’s biomass needs to be increased or decreased can help us solve the problem.

Improving our groups

Groupings are only as good as the information used to build them. Oftentimes information on a species’ feeding or reproduction only comes from one study. However, species traits are plastic—they can vary through space and time. For widely-distributed species, scant life history information may lead to poor classifications.

As we continue to learn more about the basic biology of fishes, our groupings will become more precise so that we can better predict fishes’ response to environmental change and nonnative introductions.

*Goldstein, R. M. and T. P. Simon. 1999. Toward a united definition of guild structure for feeding ecology of North American freshwater fishes. Pages 123-220 in T. P. Simon, editor. Assessing the Sustainability and Biological Integrity of Water Resources using Fish Communities. CRC Press, Boca Raton.

**Balon, E. K. 1975. Reproductive guilds of fishes - proposal and definition. Journal of the Fisheries Research Board of Canada 32:821-864.

What’s So “Great” About the Great White Shark, Anyway?

2013-08-05T06:50:00.001-04:00

Don’t you hate it when radio stations play a song that you really like so much that eventually you can’t stand to hear it anymore? What may have been a legitimately great song gets over-played to the point that its quality becomes diminished somehow. That’s how I feel when it comes to Shark Week and the Great White Shark. Is it possible that the perennial hype and focus on this one particular species is diminishing its “greatness?”

But before we go any further, some technical clarification is needed. Most shark scientists refer to Carcharodon carcharias by its official common name, “White Shark.” I think calling them “Great Whites” was something that stuck in the public’s mind when that’s how fictional marine biologist Matt Hooper referred to the shark in JAWS. There is no “Lesser” White Shark, so there really is no need for a “Great” White Shark. Do you call Great Blue Herons, “Great Blues?” I didn't think so. So from here on out, they are just White Sharks. If you must, “Great White Shark” is still acceptable, but the “Great White” reference has to go.

Now that that’s settled, what is so great about the White Shark that makes it the centerpiece of Shark Week and so many other ocean documentaries? Well, you can start by asking anyone who has actually seen a White Shark up close. They can typically attest to its “greatness.” Any fisherman who has had a White Shark circle their boat considers the encounter one of the most memorable of their lives. If they took pictures, chances are they ended up on the evening news.

White sharks have a number of unique characteristics of scientific and public interest. To begin with, they are the largest predatory fish in the sea (up to ~20 feet in length). They eat big, fast-moving prey, including seals, small whales and dolphins, turtles, smaller sharks, tunas, and a variety of other fish and invertebrates. They are also warm-blooded, so can actively hunt in cooler waters than most other sharks. White sharks also occasionally bite people (averaging 1–2 fatalities per year worldwide), which unfortunately tends to dominate the public and media’s perception of these animals.

I’ve been fortunate to have participated in research on White Sharks off California, South Africa, and Massachusetts, and every close encounter is memorable in some way. They are just impressive animals. They make you feel small. They have a presence and air of confidence that is unrivaled in the marine realm. White sharks can also be legitimately terrifying if you don’t respect them, or don’t have any understanding of their true nature. An additional bonus for filmmakers is that they can be predictably observed performing dramatic predatory behaviors in several hot-spots around the globe. Therefore, maybe it shouldn’t be a big surprise that they are the superstar headliner of every Shark Week.

A large White Shark a few seconds before it nibbled the propeller of my 22-foot research boat off Point Reyes, California (Credit: Tobey Curtis)

However, does this disproportionate focus on one particularly charismatic species cloud our understanding of other sharks, and marginalize the conservation challenges they face? White Sharks have a number of spectacular behaviors (as we have now seen ad nauseam on Shark Week), but they are by no means representative of the numerous other sharks in the ocean. Other species also display astonishing natural behaviors. Many other species have serious conservation concerns, and could benefit from public support. As Shark Week has been criticized in the past for a lack of balance in education vs. fear-inducing entertainment, it could probably also benefit from more balance in the species it focuses on year after year.

A school of socially-interacting basking sharks (left, Credit: Wayne Davis, OceanAerials.com) and surface-feeding whale sharks (right, Credit: Steve De Neef) are just a couple examples of other large, charismatic sharks that would make for entertaining TV-viewing.

The White Shark is not the biggest shark in the ocean (the plankton-feeding basking and whale sharks are larger). Nor is it the most-threatened from a conservation perspective (a recent petition to list White Sharks under the US Endangered Species Act was rejected by NOAA). The White Shark is actually one of the most highly-protected fishes in the world, and it appears to be responding to conservation efforts in some places. Contrary to frequent claims, the White Shark is also not poorly-understood. Far from it. A quick search on Google Scholar indicates that since 1984, over 500 scientific publications have focused on White Sharks. The White Shark is now arguably the BEST-studied shark in the world! Therefore, shouldn’t it be about time to shift our collective focus on to some of the numerous “data-poor” fish species that have legitimate conservation needs?

It doesn’t have to be “Great White” Shark Week! A number of closely-related rays are impressive and charismatic, like this breaching Manta (left, Credit: Brian Skerry, National Geographic) and Smalltooth Sawfish (right, Credit: Tobey Curtis, FLMNH). These remarkable species are considered to have much higher conservation concerns than White Sharks.

Many of us still agree: White Sharks are pretty great in a lot of ways. They will continue to captivate the public, and legitimate scientific mysteries remain to be solved by researchers. But there are a lot of other fish in the sea (including at least 500 other shark species) that are worthy of more research and public attention. Many have higher conservation priority, and could greatly benefit from even an iota of attention on Shark Week and other TV programming. It is not necessarily Discovery’s responsibility to deliver this message, but it is a tremendous opportunity that continues to be squandered due to the false perception that the US public is incapable of absorbing legitimate educational material. But unless something changes, be prepared for more and more White Shark shenanigans, half-assed “experiments,” attack re-enactments, and “extreme” encounters, until all of the White Shark’s inherent greatness is diminished to no more than a carnival sideshow.

Although Discovery Channel will argue to the contrary, there is really no legitimate scientific purpose to swimming with White Sharks. It’s showboating for the cameras (Photo credit: Daniel Botelho).

What sharks would you like to see featured on Shark Week? Or better yet, what other fish do you think is deserving of its own special week on TV?

Tobey H. Curtis
PhD Candidate, School for Marine Science and Technology, University of Massachusetts-Dartmouth

Follow Tobey on Twitter @Mojoshark

References

Compagno, LJV and S Fowler. 2005. Sharks of the World. Princeton University Press, Princeton. 368 pp.

Domeier, ML (ed). 2012. Global perspectives on the biology and life history of the white shark. CRC Press, Boca Raton. 543 pp.

Klimley, AP and DG Ainley. 1996. Great white sharks: The biology of Carcharodon carcharias. Academic Press, San Diego. 517 pp.