It has been almost four decades since Chris Newbert’s portrait of a long-armed oceanic octopus took my breath away. More than captivating, the magical image gracing his 1984 classic Within a Rainbowed Sea, proved transformative, opening my mind to the previously unimaginable idea of searching for pelagic animals in open ocean at night. Unfortunately, envisioning Chris drifting in open ocean at night somewhere off the coast of Kona, tempered my enthusiasm. There just seemed to be too many unknowns.

In the mid-1990s Anna and I attempted a less courageous workaround for photographing larval fish for the first edition of Reef Fish Behavior. The venture took place during our three years in Bimini where we had access to a boat and an oceanside cottage. Along with three friends from the mainland we headed for the edge of the Gulf Stream at sunset equipped with lights encased in Styrofoam, two long-handled pool nets, an assortment of buckets, dusty jelly jars from the cottage cupboard and a 12-volt car battery to power the enterprise. Surprisingly our scheme worked! 

Within minutes of connecting the alligator clips to the battery, a flurry of larvae and settling fishes fluttered around the floating lights. In no time at all a dozen strange little fishes buzzed inside our bucket. Happy with the haul, we headed to the shallows where we took individual hostages to the bottom and set them free with the hope of taking their pictures. The tiny translucent butterflyfish, quarter-sized surgeonfish, and the prize of the catch, a blunt headed flying gurnard, cooperated nicely bouncing around in a daze while the more hydrodynamic captives fled in a flash, the instant the lid was unscrewed.

Thinking back now some 25 years later, I find it disappointing that even with a boat and an able crew at hand, the idea of drifting at night like Chris was never considered. Making our lack of vision even more nettling, we were well aware that blackwater charters had been safely operating out of Kona on the Big Island for some time. We just couldn’t make the leap. What a pity.

Blackwater diving picked up its game in 2014 when two boat charters began scheduling open water night drifts off Palm Beach, Florida—less than a half-day’s drive from our front door! After a few fledgling dives it became apparent that diving in calm night seas with an experienced operator at the helm—whether tethered or untethered—turned out to be far less dangerous than perceived. We became hooked. Branching out we began visiting overseas concessions that have taken up the challenge of providing safe access to a new frontier (see our 2020 post about our blackwater diving in Anilao).

Riding the crest, Anna and I took a Covid test in early June and joined Steven Kovacs, a talented blackwater photographer from Palm Beach, for a week of night drifting off Kona, where it all began. We were there at the invitation of Al Rector, who had caught the blackwater diving bug and had access to a boat that could accommodate our nightly multi-dive schedule.

One of the first things we did after unpacking was trim a 40-foot line with lights staged at ten-foot intervals. Al had prearranged with our boat captain to have a rope, a large orange float and a ten-foot metal chain to stabilize the line, ready and waiting. Steve added a suitcase full of underwater lights, adjustable clamps and tie-wraps. Two hours later, what looked like an erector set on a rope was carefully wound into a plastic tub. Steve’s glowing mother ship worked like a charm, allowing us to swim freely with confidence while searching for scattered bits of larval life designed not to be found.

In Kona, like most destinations, we were carried by currents that were at times so strong we traveled five miles during an hour’s dive. Surprisingly, we were only vaguely aware that we were moving at all—the untethered divers, the line, the ball and the boat, all subjected to the same flow rate, calmly sailed along as a unit. With so much light power deployed, the captain could easily keep tabs on the lighted line and each diver’s position. A primary concern for blackwater divers is rough seas. Anything above a 3- to 4-foot chop makes it difficult to climb back aboard a bouncing boat. Strong surface winds that accelerate the movement of the floating surface ball and attached line are also avoided. Fortunately, Kona is known for exceptionally calm waters. Our group didn’t miss one of the 21 scheduled night dives during our ten-day stay.

On our first dive the first night, we were over the side with a splash and down to 40 feet within seconds, where we stabilized and began glancing around. The lighted line hung thirty feet away glowing reassuringly through a shadowy, seventy-seven degree sea, peppered with distracting particles of marine snow (suspended organic detritus) and pulsing jelly plankton of every description. The animals we were after were out there somewhere hiding like ghosts among a profusion of reflective debris and streaming tentacles. Our job was to find them. 

As luck would have it, we struck gold on our first dive in the form of five paralarval Ornate Octopuses —Chris’s inspirational long-armed sensation of 1984, which proved to be the progeny of a wide ranging Indo-Pacific inshore species. The first octopus appeared right away hanging as still as a painting and staring straight into my eyes. The others materialized at intervals over the course of the hour-long dive. 

Finally eye-to-eye with the icon of my dreams, so bold, so wary, approaching and withdrawing again and again, vacillating between curiosity and fear. Realizing our fortune, we stayed with and worked each in turn as long as they allowed. Our decision to give our dive over to a single species proved right and a lesson relearned. On our remaining 20 drifts in Kona we only encountered one other Ornate—just one of many treasures we would never have encountered without stretching our wings and flying off to Kona.

What else were we hoping to find at night in Kona? The short answer: dramatic, seldom-seen forms of marine life. Many of the most outrageous are the larvae of deep-sea dwellers feeding in the fertile upper reaches of the ocean during their formative weeks of life—Steve’s forte. These otherworldly oddities are few and far between and require a lot of time to track down. An intriguing assortment of larval shore fishes and invertebrates, primarily the offspring of coral reef dwellers, were more common, and often every bit as ornate. We also kept a lookout for the paralarvae (larvae maturing into adults without metamorphoses) of squid and octopuses. Several of the most exquisite species nimbly weaved their elastic arms into a high state of symmetrical art when bathed in our hand lamps.

While small, solitary oceanic squid are coveted for their photographic appeal, the larger and more numerous shoaling species often become distractions. On several dives, teeming shoals of excitable, eight-to nine-inch Purpleback Flying Squid, disoriented by our array of lights, torpedoed past at the edge of darkness. The phantom throngs often left in their wake a topsy-turvy seascape of unnerving clouds resembling flak fields from antiaircraft fire. These masses of melanin and mucus—a defensive adaptation employed to confuse predators—ranged from dark strands of wisp to thick pseudomorphs the size of soccer balls. On one sizeable flyby a Purpleback blindly crashed into my spotting light leaving behind syrupy coils of ink dangling from my strobe cords.

Our Kona expedition produced a photographic bounty of deepwater whalefishes (Cetomimiformes) larvae in families Cetomimidae (2) & Barbourisiidae (1), all sighted by Steve. Making the discoveries even more fascinating, researchers had only recently determined that what was long believed to be three different whalefish were in fact radically different life stages of the same species. The long-tailed copepod-eating oddities we photographed, known as tapetails, are actually sexually immature larvae that eventually metamorphose into either small, free-swimming deepwater males, or beefy, bottom-dwelling females with long, tooth-lined jaws and super-sized stomachs for capturing and consuming fishy prey. In the landmark 2009 whalefish paper the lead author, David Johnson, a research zoologist at the Smithsonian, wrote: “We resolve a long-standing biological and taxonomic conundrum by documenting the most extreme example of ontogenetic metamorphoses and sexual dimorphism in vertebrates.”

The offspring of deepwater cusk eels and dragonfishes we found—collectively referred to as exterilium larvae—trailed outlandish external guts of various lengths. Researchers are not exactly certain why larvae developed such odd adaptations. They could possibly function to absorb dissolved nutrients from seawater, or mimic the frilly appendages of jelly plankton.

The Kona waters also concealed a rich array of larval crustaceans, most noticeable were crabs, lobsters and shrimp. While tough-as-nails crab larvae are independent, impulsive sorts that whiz by our lights like bullets, the delicate, more sedate, see-through lobster and shrimp frequently catch rides on passing jelly plankton. Far from stable, the reluctant shuttles routinely go into tumbling spasms to dislodge their unwanted hitchhikers. 

Heavily armored in chitinous bumps, ridges and stiletto-sharp spines, it’s not surprising that the rarely encountered pelagic larvae of this deep-water shrimp I photographed near the end of our trip took more than 180 years to be properly classified by science. When originally found in the gut content of a dolphin in 1828, its discoverer characterized the remarkable creature as a “monstrous and misshapen animal” and placed in it own genus and species, Cerataspis monstrosa. It was only later in the century before scientists realized that marine crustaceans went through an early mid-water pelagic life stage. Finally, in 2012 DNA analysis linked the oddity with its adult life form—a typically shaped, circumglobal, five-inch shrimp, Plesiopenaeus armatus, that makes it home thousands of meters below the surface.⁠⁠

Want to know more?

Follow us on Instagram: @blennywatcher and @steven_kovacs_photography

References:

Jeff Milisen: A Field Guide to Blackwater Diving in Hawaii

Johnson GD, Paxton JR, Sutton TT, et al. Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families. Biol Lett. 2009;5(2):235-239. doi:10.1098/rsbl.2008.0722

Bracken-Grissom HD, Felder DL, Vollmer NL, Martin JW, Crandall KA. Phylogenetics links monster larva to deep-sea shrimp. Ecol Evol. 2012;2(10):2367-2373. doi:10.1002/ece3.347

Bonaire, 2009 – Hatching jawfish eggs! A male jawfish has guarded these eggs in his mouth for close to a week, and we managed to photograph and video them hatching. It only took fifteen years to get the shot!  We fell in love with jawfish in 1995 in Bimini. The first magazine article that Ned and I wrote together for Ocean Realm magazine was about Yellowhead Jawfish, Opistognathus aurifrons (a link to a scanned copy of the 1995 article is at the end of this post).

When we decided to write our Reef Fish Behavior book, we devoted many dives to observing jawfish behavior. We captured images of jawfish courting, jawfish fighting, jawfish building burrows, male jawfish guarding eggs – but no hatching. After we published the first edition of the book in 1999, we moved on to other projects. We finally decided to try again in 2009, during our annual stay in Bonaire.

Males exercise an extreme form of parental care by holding bundles of fertilized eggs in their mouths, occasionally partially spitting them out and quickly sucking them back in to aerate the mass of developing embryos (a behavior known as churning). They guard their broods for up to a week but we were never able to catch one in the act of releasing hatching eggs. Early on we saw a photo of a Pacific species and were told it happened just before sunrise, and were later told that it was the same for the Caribbean species. This bit of misinformation got us out of our bed at 5 AM to make several unsuccessful pre-dawn dives. 

At the beginning or our 2009 Bonaire stay, Ned called our friend Ellen Muller to ask if she could offer any clues. “Thirty minutes after sunset,” was her reply. This was at the beginning of a five-week stay, so we had plenty of time to stake out jawfish. We found colonies in front of Buddy Dive, and at several additional popular dive sites up and down the coast. Basically any sandy shelf along the edge of reefs that we dived, had Yellowhead Jawfish. 

We searched for males with bulging jaws – something that can be seen from a distance once we developed a proper search image. Males guarding eggs seem to be more wary than normal, and if spooked into their holes, can take quite a while before reappearing. Once we discovered a male with eggs, we crept closer to check out the eggs’ color. If yellow, i.e., full of fresh yolk, we figured we had a few days to wait for further development. When a mass of embryos turned dark silver, indicating enlarging eye pigment, hatching became imminent. We marked the spot with loose pieces of rubble to guide our return just before dusk. 

On any given day, we identified several potential targets with well-developed silver egg bundles, but of course they were located at different dive sites up and down the coast. So we would make a guess, picking an individual with the darkest eggs or one we’d been monitoring the longest, and from dusk to well after dark, lay in wait for a hatching. Ten days later, still no luck.

I was not with Ned the evening he finally got the shot. Instead I was sitting in the Buddy Dive traffic circle with friends, waiting for him to return from what was supposed to be a quick check on a jawfish before we all headed out for a night dive at Salt Pier. Thirty minutes late, Ned rolled up, popped out of the truck cab with a Cheshire cat grin, and did a jig. I spent the Salt Pier dive shaking off the annoyance that I missed the long-awaited event. 

Back at the room, Ned explained that he really didn’t expect success until he shined his light down the burrow opening and found the jawfish wedged inside, just below the entranceway. A light bulb went on. We already knew that prior to bedding down for the night jawfish routinely pull a rock or other piece of debris over their holes for protection. While all the other jawfish in the little colony had already capped their holes for the night, Ned deduced that the male he was observing hadn’t covered his hole because he might be ready to release his mouthful of hatchlings! Ned felt certain this was the night, but each time he snapped on his strobe’s modeling light, the male retreated deeper underground. We don’t use red lights – much marine life isn’t bothered by red light – but one might have come in handy this time. He prefocused his camera (he shoots all manual) then held his camera away so the modeling light filtered through his fingers, barely lighting the burrow entrance. With less light, the jawfish emerged within minutes and began huffing and puffing, releasing batch after batch of freshly hatched larvae with each jerk of his head. Once the eggs started hatching, the jawfish appeared to be committed and didn’t disappear down his hole even when Ned swung his camera and modeling light into position and started snapping frame after frame, timed with each release.

It was now my turn to get the video – easy now that we knew the key, right? Ned felt that jawfish would not come out with my video lights glaring. I was using a tripod, so once set up, repositioning would be difficult. I decided to try setting up the tripod, focusing on the burrow entrance, aiming the lights, then using my hands to dim them, much like Ned had done earlier. Even though I located several jawfish papas-to-be, it still took three weeks to capture the video.

The first attempts were rather Keystone Cops-esque. We arrived at a marked fish, only to find that it had covered its hole for the night. In these cases we would rush out of the water, throw our gear into the truck, and quickly drive to the next site!  What had originally seemed like a sound strategy wasn’t working. I finally found what I believed to the perfect jawfish on Buddy’s Reef, at 20 feet. Unfortunately, it was where divers began their shore dives, and every time they swam over where I was kneeling on the sand, my already nervous subject disappeared deep inside its burrow for 10 minutes or so. Two and a half hours later, low on air and camera battery, I swam back to shore. When I checked on the fish the following morning, it was up in the water column above its burrow, eggless and merrily picking plankton.

There were other frustrating dives, at times disrupted by nosy Tarpon, opportunistic soapfishes, and foraging Sharptail Eels. I confess to swatting a Tarpon or two that swooped in too close, startling both me and the jawfish. Disgruntled by a wayward swat, one big Tarpon let out a percussive boom that nearly gave me heart failure, and sent the jawfish scrambling deep inside his burrow never to return. 

I was becoming even more antsy and a bit crazed when everything finally fell into place one night on the slope at Front Porch, just down the road from Buddy’s. The jawfish hadn’t covered its hole so I quickly positioned my video and let it roll with the lights aimed but turned off. Earlier attempts of screening the bright lights with my hands just hadn’t worked. Settling a body length away, I screened the beam of a weak spotting light through my fingers, barely illuminating the quarter-sized hole, and waited. Things weren’t quite as perfect as we’d hoped – a brisk current kept the lights and tripod wobbling. The instant I realized the jawfish was releasing his eggs, I switched on the video lights. To my relief, the jawfish continued to jerk his head, releasing wave after wave of tiny larvae. My woes weren’t over. The bright video lights attracted a swarm of demented silversides. At one point the infuriating finger-sized fish flew into the scene, sending the startled jawfish out of sight. Thankfully his translucent larvae kept coming, somersaulting out of the opening and disappearing into the night. One unfortunate silverside managed to knock itself silly on my housing, flopping weakly in the foreground (a little video editing took care of that) but the jawfish, committed to releasing its eggs, carried on.

We left Bonaire two days later with the images of a Yellowhead Jawfish hatching eggs we had been long seeking. They were later added to the jawfish chapter in the second edition of Reef Fish Behavior, published in October 2019. Ned wrote his account of getting the shot in “Bonaire: A Naturalist’s Dream”, published in the Winter 2010 issue of Alert Diver.  A pdf of our 1995 Ocean Realm article is here.

Solomon Islands, Bilikiki Cruises ~ After a week of smooth sailing we wake at 6 a.m. to overcast skies and threatening seas at Kicha Island, the westernmost stopover on our Solomon Islands’ itinerary. All I can make out of our anchorage through the cabin’s rain-splattered porthole is the shadowy silhouette of a craggy volcanic island being battered by surge—I roll over and groan. The idea of squeezing into a still-wet wetsuit to make the unusually early morning dive on a dark submarine wall in sloppy seas nearly keeps me in my bunk. But eventually the smell of coffee entices me above deck where I’m greeted by zombie-eyed shipmates clutching steaming cups beneath a dripping tarpaulin. In the distance waves crash, and above, the ship’s pennants pop in a freshening breeze. The skiffs, already secured to the dive deck for loading, buck at their ropes like broncos. My mind fumbles for an excuse, any excuse, to stay aboard and enjoy a second cup of coffee. But when a handful of friends start gearing up I relent and add my name to the dive manifest. 

A half hour later, at 40-feet, the wall is even gloomier than imagined. Dismayed, and second-guessing my decision, I swim back up the slope, slip over the crest and cut toward the island in the hope of finding some light. But instead, I swim into a barren moonscape of black rock stretching all the way to shore. Just as I’m thinking of signaling the skiff driver for an early pickup, something big moves off in the haze. I drop to the bottom like a stone. Shadows steal past on my left, and others to my right.

Suddenly I realize that I’ve blundered into a herd of Bumphead Parrotfish, Bolbometopon muricatum. Dumbstruck by luck, and well aware of the burden of such a great opportunity, I hunker down and try to figure out my next move. I‘ve dived with these giants before, but have never been able to get anywhere near this close. Suddenly it dawns on me: the parrotfish are waiting for their turn at a cleaning station and reluctant to leave.

In the center of the grand affair is the largest bumphead I’ve ever seen, a four-foot colossus hovering above an outcropping with it fins outstretched like royalty being attended to by a bevy of parasite-picking hogfish. That’s the photo I want. The trick will be getting closer. As soon as I make my move, the already edgy herd begins to swirl. Unnerved I press my luck, angling up until I’m eye level with the brute, but my move is early and awkward, causing the great fish to bolt for open water. Realizing I’ve blown the shot, the dive, and the day and not knowing what else to do, I race after the fish with no particular result in mind. Reaching the wall the fish turns, paralleling the ridge. 

Out the corner of my eye, I catch a glimpse of friend, Christina Rudman, leisurely heading my way. I wave like a madman, catching her attention as the parrotfish streaks in her direction. As if born to wrangle bumpheads, Christina cuts off the path of the speeding fish, turning it on a dime, and escorts the amazing animal back along the wall in my direction. At that moment a second cup of coffee is the furthest thing from my mind. ~ Ned DeLoach, November 2009

Eye-to-Eye with Cute

If it hadn’t been for a bit of movement, we would have never seen the pair of coralgobies living inside a fortress of branches fashioning a soccer ball-sized mound of cauliflower coral—one of hundreds of similar colonies fringing the knee-deep, inshore shallows of Ambon Bay in Indonesia. With our facemasks only inches away, two of the cutest fish in the sea scampered about their symbiotic home like mice in a maze. After several seconds of diver-induced panic the pair of Redheaded Coralgoby, Paragobiodon echinocephalus, settle down side-by-side in the shadows and peer up with big, beautiful, beseeching eyes imploring us to just go away. The inch-long fish, with fuzzy red heads, bright green eyes and roly-poly bodies shot Cupid’s arrows straight into our hearts. Not wanting to bother them further, we obliged, slowly finger walking our half-submerged bodies hippo-style along the outer fringes of the reef searching for gobies as we go. 

To our delight, we found ourselves in an unfamiliar fantasyland of seldom-seen fishes, including four additional members of the forever-cute coralgoby clan comprising two genera: Gobiodon and the shaggy-headed Paragobiodon. The discovery of so many new species would be a boon for expanding the photo galleries in our Tropical Pacific ID book. But, at that moment business was far from our minds. All we were thinking about while wading back to our skiff was how to get a photograph of the amazing pair of redheads—an intriguing image to top off our month-long jaunt across eastern Indonesia. 

Our major concern was a tight flight schedule home, which left us only a single day to get our shot. Fortunately, we still had our private boat booked. While slinging tanks into the boat, Semuel Bukasiang our guide for the week, and a veteran of distinction, estimated that high tide, optimal for shallow inshore diving, would reach its peak in the early afternoon. As our skiff skimmed back to the resort over water as smooth as a proverbial millpond everything was set, or so it seemed. At that moment, with images of gobies still dancing in our heads, neither of us had an inkling of the storm rumbling its way up from the Indian Ocean, or of the bruises and life lessons that awaited. 

The following morning we awoke to a freshening gale. By the time we descended the steps of our bungalow at 7 AM a brisk sea breeze had been sending spray over the seawall for an hour. Word of worsening conditions arrived with coffee. Minutes later Semuel joined us with an even more unsettling forecast along with a pressing decision. It seemed our only chance to visit the gobies would be in the coming hour, and even then conditions, especially carrying a camera in the surge, would make for some tricky diving. Driven by greenhorn grit, Anna and I, without hesitation, agreed to go for it. 

As expected, the shallows were in a rage when we arrived. Making matters worse the tide, only beginning to rise, exposed a patchwork of coral tops in the troughs between waves. The three of us, not quite sure what we were getting into, backrolled into the uproar, struggled to our feet, and staggered unsteadily toward shore. Anna was first to go down. Semuel and I quickly followed, upended by a wave that carried us across the bottom like leaves in a gale. Once near the edge of the reef and semi-stable on our hands and knees, the three of us set about searching for gobies as best we could. 

Within minutes, Anna spotted a pair of Redheads. Purging the last drop of air from my BC, I settled on the sand inches away from her pointing hand, dug my elbows into the bottom, and began searching for the tiny targets through the sand and debris. Even with a full tank and the eighteen pounds of weights scavenged from the dive shop floor, holding steady long enough to take a photo was proving next to impossible. 

Just as I caught a glimpse of Anna’s gobies an explosion of surge catapulted me onto my back. Righting myself, I crept back into position and hunkered down with renewed determination. Eventually the skittish pair settled down cheek-to-cheek just like the day before. But, try as I might, I couldn’t get a clear shot through the branches. Adding to my troubles, the surge was picking up, the sky was darkening and rain began peppering the back of my head like buckshot. Frustrated, fatigued and getting nowhere fast, I began circling the coral occasionally catching sight of a goby tucked deep in the tangle. Finally, sprawled flat and craning my neck, a small passage leading to what happened to be one of the gobies’ favorite perches appeared. But when I lifted the camera, the pair, with no intention of having their portrait taken, bolted to the other side of the coral head. The small opening leading to the perch seemed to be my only hope. There was nothing to do but wait.

Noting my predicament, Semuel settled on the sand across from me, and with a wave of his fingers sent the gobies scrambling in my direction. After several tentative passes they eventually perched right where I wanted them and stared into my lens with the soulful eyes of puppies in a pound. But before I could focus, the surge lifted my legs off the bottom and wrenched the viewfinder from my eye. By the time I regained composure the gobies were gone. This back-and-forth battle of wills between man and goby, that only lasted minutes, seemed to stretch into hours. All would have been lost had it not been for Anna — the best buddy a diver ever had. She came to the rescue, draping her tank-heavy body across my wayward legs—just the trick to save the day.

2012 – The Coralgoby Hunt Begins

Our blundering, but none-the-less consequential encounter with the Redheads set into motion a yearlong quest to photograph every species of coralgobies we could find. We had to wait until spring to get started. When the time came we headed back to Indonesia, primarily Raja Ampat, Lembeh Strait and the Banda Sea. 

In Raja Ampat, Yan Alfian our guide of long standing aboard the Dewi Nusantara took to goby hunting with gusto. Once underwater, and into the mission, we were delighted to discover that coralgobies were more common than supposed, and even more surprising, inhabited depths down to 25 meters. However, inshore coral thickets, from the surface to four meters, consistently proved to be our most bountiful hunting grounds. Unlike the isolated mated pairs living in Ambon, we often encountered clusters of the same species living on a single coral head, while other colonies accommodated multiple species.

From day one, lessons learned in Ambon served us well. Notably, we never again ventured into the shallows except on rare days when the winds and surge settled and the inshore water calmed to a glassy sheen. We typically limited our search to small corals a foot or two across to minimize the area where the gobies could hide, and only worked colonies surrounded by sand—essential etiquette for diving in a fragile universe. After finding a species of interest, we immediately set about looking for a breach in the branches leading to perching places. If not found, we quickly moved on. Frequently a dozen or more inhabited colonies were inspected before a potential opening was found. Besides a clear view, these unrestricted passages allowed my single strobe’s beam to reach the subject without creating harsh shadows.

The tedious task of wrangling one-inch gobies on their home turf requires cunning, dexterity, determination, and patience galore. Once Yan selected a target, he began shooing the goby in my direction. These cat-and-mouse competitions could take the better part of a dive to complete. My part in the game was limited to holding focus on a vacant perch while Yan’s worked his magic.  

The taxonomy of reef gobies is far from complete. Currently around 30 Gobiodon, and less than ten closely related Paragobiodon species from the western Pacific, Indian Ocean and Red Sea have been scientifically described. Fieldwork and photographic evidence suggest a significant number of species remain undiscovered and undescribed. Our amateurish attempt at species hunting logged 12 described Gobiondon and six Paragobiodon species from Indonesian waters, along with a single undocumented Gobiodon from Lembeh Strait and a lone mystery Paragobiodon found living outside Ambon Bay. A number of photos from our efforts currently adorn the coralgoby section (pages 332-335) of Reef Fish Identification—Tropical Pacific. 

A Short Origin Story

It would seem that such a small, simple life, lived out within such small, simple surroundings, would be simple, but like everything else in nature it’s delightfully not. And indeed, like all other forms of life studied extensively coralgobies also have an enchanting story to tell. Their history, driven by an irrepressible itch to fill a fertile ecological niche—in this case shallow coral gardens—began long ago in a forgotten time. The drawn-out quest powered by the adaptive forces of natural selection eventually came to pass.

While most small, short-lived members of the extensive Gobiidae family build burrows or rely on hiding holes for protection, coralgobies limit predation by living exclusively within the tightly knit networks of fast-growing, sun-worshiping, shallow-water branching corals. Adding an extra layer of protection, the scaleless, mucus-laden skin of many species contains clusters of poison cells. And, like other gobies living in high-current habitats, the coralgobies’ two ventral fins have grown together and developed small suction cups to hold them securely in place during blustery conditions. 

As partial compensation for their hosts’ protection, coralgobies help keep polyp-nipping butterfly fishes at bay. In a paradoxical twist: Stomach analysis of field-collected specimens indicates a primary diet of both free-swimming and parasitic copepods (tiny, shrimp-like crustaceans), supplemented with a healthy portion of purloined flesh from their coral hosts.   

Sex change (hermaphroditism) from female to male (protogyny) and to a lesser extent from male to female (padandry), is frequently employed to help stabilize social structures of fish populations, primarily in the wrasse, sea bass, anemonefish and goby families. Aquarium experimentation in the 1990s revealed that coralgobies have the unconventional ability to change sex more than once (bi-directional sex change) during their lifetimes—the only group of reef fishes presently known to do so. The norm-breaking lifestyle to improve reproductive success appears to be an artifact of isolation. Researchers studying the social structure and sex life of a natural population of the common Red-barred Coralgobies, G. histrio on the Great Barrier Reef uncovered several other surprising nuggets of interest. 

Detailed surveys of the study area determined that more than 80 percent of the platter-shaped plate corals, Acropora nasuta, was occupied by either a single immature female, or a mated adult pairs. This led the authors to speculate that settling larvae and adult immigrants from surrounding colonies were driven away from the established breeding grounds of territorial pairs. This dominant control of prime real estate left only a small numbers of vacant corals, or those inhabited by solitary immature Red-barred residents, open for colonization. Under these limiting circumstances the ability to change sexual orientation in either direction increases the likelihood of a vagrant of either gender forming a breeding pair.

After establishing control of a coral head, mated pairs, which in this case were found to be equal in size and able to maintain long-lasting bonds, turn into breeding machines. For four consecutive days males guard egg patches laid by their mates at the bases of branches nipped clean of polyps while their progeny mature. Only a day or two after hatching females deposit another fresh clutch for safekeeping. This ongoing reproductive cycle continues uninterrupted throughout the breeding season.

Without a doubt coralgobies’ most amazing evolutionary adaptation enables the little fish to remain inside their coral homes even when they become high and dry during annual spring tides. It is believed that coralgobies can survive for up to four hours out of water by an adaptation unique to the group. As the water level drops resident gobies nestle in the shade of branches and begin circulating a small volume of water through their mouths and over the gills’ blood-rich lining where oxygen is absorbed. Depleted, the droplet flows outside the gill cover and through an exterior groove distinctive to the genus, spanning the length of the lower jaw. During the transit the water is oxygenated through the diffusion of air before entering the mouth and making its way back to the gills where the cycle begins once again. The intake of oxygen through the skin might also play a role in the remarkable feat.

A Matter of Color

To advertise their poisonous nature the majority of coralgobies wear brightly patterned wardrobes—a strategy common to many colorful terrestrial and marine species. However, a few coralgobies in both genera buck the trend by displaying drab monotone colors to the world. It’s possible that these lackluster species, such as the Black Coralgoby, P melanosomus (pictured above), lack poisonous tissue, but no one knows for sure. 

From personal observation, the Golden Coralgoby, P. xanthosoma, or (Should the common name be Emerald Coralgoby?) has the ability to change their color back and forth between yellow and green in a matter of minutes. For whatever reason, no one yet knows. The little illusionists live exclusively in mated pairs within Birdsnest Coral, Seriatopora hystrix. These densely branched shallow-water hideaways create such inaccessible strongholds that I put off photographing the species for months. My reluctance took a turn in Raja Ampat when an irresistible yellow face peeking out of the branches caught my eye. After downloading my images, a yellowish head generously tinted with green splashed across my screen. At the moment I blamed the anomaly on Photoshop, and left it at that.

We were back in Ambon during a stopover between voyages when Golden Coralgobies next came to mind. During our brief visit we had an opportunity to explore the inshore shallows on the far side of the bay for the first time. Four feet deep and thick with coral from sand to the surface, the reef epitomized goby terrain, but Anna was nowhere to be found, off with the guide working on another one of her many esoteric projects I reckoned. Fortunately, there are so many gobies around that I could find them for myself, and most just happened to be Golden Coralgobies. In fact, the species was so abundant I decided to put some effort into getting the long postponed ID-shot. 

I concentrated for the better part of an hour on a single coral head sheltering a bright yellow pair. Seldom on their perch, the occupants I was tracking kept on the move deep within the branches. While investigating the routes of their convoluted runs I noticed one of the gobies occasionally taking a shortcut through an exposed gap on the coral’s outer edge—not much of a chance, but a chance nonetheless. Each time the goby raced through the opening I snapped the shutter. Glancing down at the screen between shots I noticed an ever-darkening flush of green spreading over the goby’s yellow coat. By the time Anna and the guide returned with the boat the once Golden Coralgoby had transformed into Emerald Coralgoby extraordinaire. 

Another question about color change has to do with Lemon Coralgobies, G. citrinus—at two-and a-half inches one of the largest coralgobies around. Mated pairs and small groups of these giants among their kind set up housekeeping inside large open Acropora colonies where they boldly perch out in the open on the ends of branches exhibiting marked indifference to passing divers. One would suspect that their bravado had something to do with being somewhat large in a Lilliputian world, coupled with poisonous tissue, clearly broadcast to predators by their bright color. This makes one wonder: If this wonderful eye-catching adaptation is so effective at warning away predators, why would Lemon Coralgobies engender a black variation? Also after scanning goby literature, it never became clear whether black individual are immutable, or like the Golden Coralgoby have the ability to change their color at will. Seems like another mystery remaining to be solved by an inquisitive aquarist, a savvy underwater naturalist or an overworked graduate researcher, or a combination of the above.    ~ Ned DeLoach

CoralgobyReferences

Munday, P. L., Caley, M. J. & Jones, G. P.  “Bi-directional sex change in a coral-dwelling goby.” Behavioral Ecology and Sociobiology 43 (1998): 371-377.

Munday, P. L., Jones, G. P. and Caley, M. J. “Habitat specialisation and the distribution and abundance of coral-dwelling gobies.” Marine Ecology Progress Series 152 (1997): 227-239.

Munday, P. L., Jones, G. P. and Caley, M. J. “Interspecific competition and coexistence in a guild of coral-dwelling fishes.” Ecology 82, (2001): 2177-2189.

Munday PL  “Bi-directional sex change: testing the growth rate advantage model.“ Behavioral Ecology and Sociobiology 52 (2002): 247–254

Munday, P. L., Cardoni, A.M., & Syms, C. “Cooperative growth regulation in coral-dwelling fishes.”  Biology Letters, 2(3)(2006): 355-358.

Kuwamura T., Yogo Y., Nakashima Y. “Size-assortative monogamy and paternal egg care in a coral goby Paragobiodon echinocephalus.” Ethology 1 (1993): 65–75.

Kuwamura T., Yogo Y., Nakashima Y.  “Population dynamics of the goby Paragobiodon echinocephalus and host coral Stylophora pistillata.” Marine Ecology Progress Series 103 (1994): 17–23 

Nakashima Y, Kuwamura T, Yogo Y (1996) “Both-ways sex change in monogamous coral gobies, Gobiodon spp.” Environmental Biology of Fishes 46 (1996): 281–288

Lassig BR, “Significance of the epidermal ichthyotoxic secretion of coral-dwelling gobies.” Toxicon 19(1981): 729–735 

Lassig BR “Field observations on the reproductive behaviours of Paragobiodon spp. (Osteichthyes: Gobiidae) at Heron Island Great Barrier Reef.” Marine Behaviour and Physiology 3(1976): 283-293.

Lassig BR, “Socioecological strategies adopted by obligate coral-dwelling fishes.” Proceedings of the 3rd International Coral Reef Symposium (ICRS), (1977): 565-570.

Goran E. Nilsson, Jean-Paul Hobbs, Phillip L. Munday and Sara Ostlund-Nilsson “Coward or braveheart: extreme habitat fidelity through hypoxia tolerance in a coral-dwelling goby.” Journal of Experimental Biology 207 (2004): 33-39

Time to say “Bye” to 2020 with some of our 2020 social media favorites. We certainly had plenty of time to sift through old files and dabble. I wish we had more to say about diving (sigh), though we did manage to slide in two trips – one to the Philippines before the pandemic lockdown, and a quick, socially distanced trip to West Palm for a few days in July.

A friend recently commented that if we’re posting anything “on the socials”, she doesn’t see it because she isn’t in Facebook, Twitter, or Instagram. We aren’t devoted participants – we’re absolutely inconsistent in subject and timing – but over the years, I’ve shared a few things on our BlennyWatcher Facebook page. We started an Instagram page a few months ago that gave me a place to post some of my favorites of Ned’s images from over the years, accompanied by the odd note or two that I stored away for just such a use.

Our 2020 Social Media Favorites:

Not as cute and innocent as they look, Bumblebee Shrimp feed on the tube feet of echinoderms which explains why we find them on sea cucumbers, urchins and starfish. This was photographed in Beangabang Bay, Indonesia at night, on a sea apple (a type of sea cucumber) that had all its feeding tentacles retracted. This photo on the right was taken during the day, and this Sea Apple has its feeding tentacles extended. A type of sea cucumber in the genus Pseudocolochirus, the sea apple uses bushy tentacles that surround its mouth to catch microscopic food as it passes by in the water.

This species, Gnathophyllum americanum, is said to be circumtropical (we’ve also photographed them in Florida and the Caribbean) but it might be a species complex – that is, populations in different geographic areas that are very similar in appearance, but genetically different. Formerly placed in the family Gnathophyllidae, they are now in the family Palaemonidae.

What is this Bumblebee Shrimp doing on an octopus? I posted earlier about them feeding on the tube feet of echinoderms, which explains why we find them on sea cucumbers, urchins and starfish, but an octopus was a first for us. During the course of the dive, we saw six shrimp running all over and under the unperturbed octopus

Photographed in 2015 under the Blue Heron Bridge, Riviera Beach, Florida.

Above Left: The Bignose Unicornfish, Naso vlamingii, photographed on Tania’s Reef in Papua New Guinea. These fairly large members of the surgeonfish family are usually seen feeding out in open water just off the reef. This fish had come down to the reef, presumably to be cleaned.  Described by Valenciennes in 1835 and named for Cornelis de Vlamingh, a Dutch explorer (1678-1735) who had mistakenly received credit for the illustrations used by Valenciennes to describe this and other fishes. When I was looking for the original 1835 description of the fish, I ran across a 1990 article in Bulletin du Muséum National d’histoire Naturelle that explains how, in 1959, it was discovered that the illustrations were actually the work of Isaac Johannes Lamotius, governor of Mauritius from 1677 to 1692.

Above Right: Here’s a dose of cute for the day: a tiny unicornfish in the genus Naso, but we’re not sure which species. This fish was only about and inch and half long. Ned saw two of them together, over the sand, just off a reef in Palau. 

Fish Face

Got Monday Morning Grumpy Face? Batfish says, “Welcome to my world.”

Do you wonder if they’re venomous? I did, but I guess not: In their 1898 discussion of the genus Ogcocephalus (which were called Sea-Bats back then), Jordan and Evermann wrote, “...small fish of singular form, often regarded by the ignorant as venomous.” They go on to criticize the original author of the genus, over a perceived misspelling: “…properly written Oncocephalus, but Fischer chose the above monstrous spelling.” Yikes! Sounds like they might have been having a grumpy Monday!

This is the Caribbean’s Shortnose Batfish, Ogcocephalus nasutus, photographed in Dominica.

Longhorn Blenny, Hypsoblennius exstochilus ~ How about those cirri! The common name needs no explanation. The protruding flaps on each side of the lower lip distinguish the Longhorn Blenny from other species in the same genus. They are especially noticeable in this head-on shot. The species name, exstochilus, means just that: protruding (exsto) lip (cheilus).

We saw many of these in the surgy hardpan shelf on the east side of Bonaire. We had intended to head out to the reef, but ended up spending three hours in the shallow channel looking at blennies.

The Ninelined Goby, Ginsburgellus novemlineatus. Why do we always see them with the rock boring urchin, Echinometra lucunter? Because they feed on the tube feet and pedicellariae of the urchins (pedicellariae are small structures, made up of a stalk and a jaw-like head, attached to the outer skeleton of the urchin).

We took advantage of a calm day to explore the shallow shelf on the south end of Bonaire. I’ve snorkeled that area extensively over the years but the water is usually too surgy to photograph fishes easily on scuba.

Described and named (novem=nine & linea=line) in 1950 by Henry Fowler, Curator of Fishes at the Academy of Natural Science in Philadelphia, from a specimen collected in 1948 off San Andrés. In 1968, this distinctive fish was placed in its own genus, Ginsburgellus, by Böhlke and Robins, who discussed its close relationship to the genera, Elacatinus and Tigrigobius but noted “most of its distinctive features are associated with its peculiar snout and mouth, which finds no close parallel in either group…” They also noted that the flattened head “is an adaptation for maintaining position on the bottom in the surf”

Ever wonder about how it got its name?

What do the Caribbean’s Sailfin Blenny and the Osprey (bird) have in common?

The first specimen of the Sailfin Blenny was collected in 1899 during an expedition aboard the steamer Fish Hawk.

In 1900, Everman and Marsh described the fish we now commonly call the Sailfin Blenny. They named it Emblemaria pandionis, and in their description said, “Named for the U.S. Fish Commission steamer, Fish Hawk, Pandion being the generic name of the fish-hawk or osprey, Pandion carolinenesis.”

What do the Arrow Blenny and Stan Waterman, celebrated filmmaker and raconteur, have in common? The name, Lucayablennius zingaro. 

The fish was described in 1957 by by James Böhlke, who wrote, “..collected by Charles C. G. Chaplin, Stanton Waterman, Edwin Brownrigg and the writer from Sta. 295, about 1/ mile north of the east end of Green Cay, Bahamas:..” and “…collected from Waterman’s boat, the Zingaro, for which the species is named…”

When I contacted Stan years ago for permission to use the photo of him on Zingaro, he wrote that he had originally considered naming his boat, the Polyp but instead chose Zingaro, from the Italian “gypsy”.

What’s in a common name?

Common names that convey a physical characteristic of a fish are helpful for fish watchers. In the case of fangblennies, we don’t often see their fangs. This one was threatened because it was guarding eggs and we got too close. Some, but not all fangblennies have venom glands. This one, the Shorthead Fangblenny, Petroscirtes breviceps, does not.

Another fish with an appropriate common name:  A Biglip Damsel, Cheiloprion labiatus – the little fish with the Hollywood lips. The Biglip Damsel feeds on Acropora coral polyps so it has likely developed that fleshy pout to protect itself against the sharp coral skeleton.

Above left: The Anchor Tuskfish, Choerodon anchorago, described by ichthyologist and physician, Marcus Elieser Bloch in 1791, and originally placed it in genus Sparus. We’ve watched these fish move large pieces of coral and rocks with those teeth in order to get to a tasty mollusk. This individual was photographed in Maluku, Indonesia.⁠

Above right: The second image is a beautiful illustration by  J.F. Hennig for Bloch’s multi-volume natural history of fishes, Naturgeschichte der ausländischen Fische

Looking forward: 2021

Ned has selected about eight of his favorite natural history stories – all previously published years ago in diving magazines – and is updating them with additional images and notes. Starting next week, and over this coming year, we’ll post them here.

He has written for several diving magazines since the late 1970s, and for a couple of years, served as editor in chief, then co-editor of Ocean Realm Magazine, before the publisher in Jacksonville sold it in the late 80s. He continued to write for the new owners, and starting in 1995, we wrote a regular column there: Underwater Naturalist. Many of those articles became the basis for our Reef Fish Behavior book, first published in 1999. The updated second edition was published in 2019 (available at Fishid.com).

We’ve written Encounters articles for Alert Diver for the past ten years. Most of those are online at AlertDiver.com (see Alert Diver DeLoach), but our bookshelves and cabinets overflow with pre-2010, old print magazines. Spending most of 2020 at home gave me the time to scan those, and I’m at nearly 250 magazine articles, with several healthy stacks yet to do. I’d have them all scanned, but it often takes over an hour per article because I have to read all the other articles and adverts in the old magazine – often quite an entertaining journey back through time.

Our original intention was to load all the scanned articles up on this site, but the scan quality of the older articles isn’t so great, or we have better images now, or we know more about the subject now, or the article had a limit on word count and we had so much more we wanted to say, or… So, we decided to load scans of a few favorite articles here on our Publications page, and as Ned reworks other favorites, we’ll post them here.

Happy 2021, and check back soon.

At first glance, adorable little boxer crabs don’t look like kidnappers, but a closer look reveals incriminating evidence—living anemones grasped tightly in each claw. As it turns out the crabs, which spend the day hiding beneath rocks along shorelines in the Indo-Pacific, commandeer hostages for gathering food as well as protection. 

This novel form of symbiosis was labeled as kleptoparasitism—the theft of food—in a 2013 scientific paper. The authors studied the relationship using aquarium experimentations and observations. In an unexpected finding, their research also revealed that the crabs intentionally starve their captives to keep them manageably small. 

To feed, the crabs use their tiny victims like mops to pick up bits of food from their surroundings. The crabs quickly remove the particles with their walking legs, leaving behind just enough scraps to keep their anemones alive, but not enough for them to continue to grow. The researchers likened the behavior to “Bonsai”—retarding a plant’s growth by manipulation. When the anemones were removed from the crabs and allowed to live on their own they grew rapidly not only increasing their size by as much as 250 per cent, but also changing their color and shape.

It generally takes a lot of tedious rock turning to find a boxer crab. With the help of our dive guide at Tulamben—a well-known dive destination in Bali—we were able to increase our odds. He knew exactly where a pair lived and was able to find us one in a matter of minutes. Exposed, the crab wields its pair of anemones like miniature boxing gloves, appearing to throw a series of jabs in our direction. Afterwards the guide carefully turned the rock back over, returning the little pugilist to its rightful place. ~ Originally published in our Critter Hunt Column in Scuba Diving magazine, 2012

On our 2012 dives in Bali, we also learned that if we dived in the rocky shallows at night, we didn’t have to turn rocks over to find boxer crabs because they were often walking around in the open. They didn’t appear disturbed by us, each other, or any predators, so it was a good opportunity  to watch them. They moved slowly, waving their anemone pom-poms from side to side, in what certainly looked more like feeding than defensive maneuvers. Whether they carry anemones for defense or for feeding, it is an intriguing story: invertebrates using tools!

We’ve also photographed another species of Lybia in Lembeh Strait. This was much smaller and fairly nondescript. In fact I couldn’t tell it was a boxer crab until Ned enlarged his image, revealing the tiny anemones in its pincers:

2020: Down the Rabbit Hole

An 1880 taxonomic study first described the association of the crabs with anemones and suggested their use for both feeding and defense. One of the most interesting notes came from a detailed study of boxer crab behavior in a 1905 paper:  a crab, deprived of one of its two anemones, would split the remaining into two pieces, so it would have one for each claw.

A 1998 study looked at the intraspecific fighting behavior of the Hawaiian boxer crab, L. edmonsoni, using 50 crabs collected from three locations in Oahu. In fighting matches, they observed that the crabs rarely touched each other with their anemones, and when they physically grappled, they fought back-to-back, holding their anemones away from each other. It would seem that the crabs were protecting their anemones from harm. Two of the crabs they collected only held a single anemone, and they experimented with removing a single anemone from two other crabs. All four were later observed to be holding partial anemones in each claw, and in one case, they actually observed the crab splitting its lone anemone by pulling it apart.

In 2017, the same scientists who wrote the 2013 paper about the “Bonsai” anemones and kleptoparasitism, ran experiments of sea anemone splitting and sea anemone theft by boxer crabs. When they staged encounters between crabs with anemones and crabs that had no anemones, 73% of the time intense fights took place, resulting in the crab without anemones managing to steal an entire or partial anemone. After the theft, the crabs separated, and were observed splitting their remaining  whole or fragment, resulting in partial anemones in each chela (watch the video from that study). All split anemones eventually regenerated, resulting in whole, genetically identical anemones in each claw. 

So how do newly settled boxer crabs obtain their “starter” anemone? The researchers collected three very small (2-3 mm) crabs, removed their anemones and put them up against fully grown crabs with anemones. Despite the big difference in size, the smaller crabs initiated a fight and succeeded in stealing a whole or partial anemone. These were all laboratory observations – wouldn’t that be something to see in the wild!

Wait…Crabs with nudibranchs?!

Years ago, when writing about the small dorid nudibranch that preys on the fins of shrimp gobies, we ran across Dr. Tune Sakai’s 1961 description of a new crab from Hanama Bay in Japan. Described from three specimens, he named it Lybia hatagumoana, placed in the genus with the boxer crabs, and named, presumably, for their research vessel, Hatagumo.  He remarked, “The holotype was carrying a tiny sea-anemone in each hand, and the allotype had a tiny nudibranch in one hand.”  What??? A nudibranch??? Was this a one-time observation? How often has this been seen? How can we see this?

Thus began our search for a nudibranch-wielding crab. There isn’t much published about them, but Sakai’s observation was more than a single, coincidental occurrence. In 1993 Kikutaro Baba described the nudibranchs found clutched in the fingers of two more specimens of Lybia hatagumoana. He describes them as  Gymnodoris sp., most closely resembling G. citrina: “The ground colour of the dorsal surface of the body slightly yellowish white in Material No. 1 and tinted more pinkish (orange yellow) in Material No. 2. The overall dorsum and sides scattered with tiny orange spots. The club of the rhinophore orange, and the stalk whitish.” 

We have yet to find any information about whether or not this nudibranch was ever given a definitive name.

There are a lot of things I still want to see underwater, and a crab holding a nudibranch is one of them. Unfortunately, my hopes were dashed when I read the only other paper I could find that mentions this unusual association: In their 2011 paper, Drs. Jose Christopher Mendoza and Peter Ng recorded the presence of the subfamily Polydectinae (the boxer crabs) in the Philippines. They also described a new genus for this little nudibranch-carrying crab, formerly known as Lybia hatagumoana: Tunebia, “named in honor of Japanese carcinologist, Professor Tune Sakai. It is an arbitrary combination of his first name and Lybia.” They note that all specimens taken to date were from depths “no less than 70 meters” – a little too deep for scuba – Darn!

Even though chances are slim that we’ll ever see this crab for ourselves, Dr. Mendoza was kind enough to grant permission to share an image from his paper, so we’ll all have the search image – just in case. Scientific studies have enlightened us about crabs wielding anemones, but how do they find nudibranchs helpful? So many mysteries; so much to learn!

Check out figure D and the nudibranch held in the left chela:

References:

Mendoza, Jose Christopher E., Ng, Peter K. L. (2011): The Polydectinae Dana, 1851, of the Philippines, with description of a new genus for Lybia hatagumoana Sakai, 1961 (Crustacea: Decapoda: Brachyura: Xanthidae). Zootaxa 3052: 51-61

J. E. Duerden (1905). “On the habits and reactions of crabs bearing actinians in their claws”. Proceedings of the Zoological Society of London 2: 494–511

Sakai, T. (1961). New Species of Japanese Crabs from the Collection of His Majesty the Emperor of Japan. Crustaceana, 3(2), 131-150

Baba, K., Noda, H. (1993) A rare collection of a small species of Gymnodoris (Nudibranchia: Polyceridae) held alive by the chelipeds of the crab, Lybia hatagumoana (Brachyura: Xanthidae), from the bottom off Kanayama Bay, Kii, Japan. Venus, 52(4), 283–289

Note: A version of this encounter was originally published in the April 2008 print edition of Scuba Diving magazine.

Day after day, fish that eat fish, known as piscivores, have a pretty tough time of it. Their primary prey, small fishes, are hard-wired wary, and over the eons have adapted strategies to counter nearly every trick. Unless something unusual happens to upset the equation, the edge generally goes to the prey. This is why great marine piscivores have become opportunistic predators programmed to take advantage of anything out of the ordinary that just might swing the pendulum in their favor. A case in point: shark feeds. 

A shark feed not only creates an unusual situation, but better yet, from the predators’ perspective it bestows a surplus of food – a rare phenomenon in tropical waters. Now I don’t intend to list a litany of pros and cons in regard to fish feeding, or present myself as a studied expert on the matter, but personally I find shark feeds a hoot—an authentic underwater kick in the britches. I have participated in six or so different feeding events around the equator and found them all to be less than moderately dangerous. And from what I’ve learned about fish behavior, the free lunches provide nothing less than a boon for the fish. Remember, the participating species are opportunistic predators; if their semi-regular offering of complimentary food suddenly disappears these super predators certainly aren’t going to starve. 

As much as I marvel at the sleek beauty of the main attraction, in the case something like 60 Caribbean Reef Sharks, I find the behavior of the satellite participants every bit as entertaining. This was certainly the case at a shark feed inside the Exuma Cays Land and Sea Park in the Bahamas several years ago. Although Caribbean Reef Sharks, Horse-eye jacks and ubiquitous Yellowtail Snappers supplied the teeming biomass, the resident population of large Black and Nassau Grouper stole the show with a fitting demonstration of what the term opportunistic predator means. 

As the sharks tore in to the suspended chumsicle (a frozen block of fish scraps) and Yellowtails darted about wildly snatching freed pieces, a 30-pound grouper screened by a sea fan bided its time near the bottom. Now and again, the wily grouper would dash up and grab an unsuspecting Yellowtail that had let its guard down. But the big winner of the day was an even larger Black Grouper that timed its wait until just the right instant before rocketing through the melee to engulf what remained of the thawing bait ball.  

Read more about Shark Feeding: https://www.sharktrust.org/shark-feeding-dives

When I became a diver, worms were among the first reef creatures to attract my attention. More accurately, it was the exposed crowns of frilly gills of Christmas Tree Worms, Spirobranchus giganteus, that drew my eye—so colorful, so appealing, so utterly unwormlike, and to Anna’s and my unending irritation, gone in a flash whenever we swam too close.

While the worms’ long segmented bodies remain tucked away safe and sound inside strong calcareous tubes, their delicate crowns, vital for absorbing oxygen and gathering food, must deal with the rigors of a dangerous world outside. To avoid being eaten or damaged, the delicate spirals retract in an instant whenever suspicious shadows or extraneous water movements are detected. Think divers. For insurance, a trap door topped with a spike slams tightly shut behind the disappearing tentacles. 

The lovely twin crowns are lined with tiny mucus-covered filaments, known as cilia. When currents are calm the cilia beat in waves sending oxygen-rich water, along with planktonic food and grit spinning down their spiraling tentacles leading to the mouth. The sand is sorted by size for later use as building material necessary for slowly extending the tubes to keep pace with the coral’s grown. If all goes as planned, worms can live for decades and grow to impressive lengths. 

In the southern Caribbean, Yellownose Gobies often live on the same coral heads, or mooring blocks where Christmas Tree Worms make their homes. The gobies obtain the majority of their sustenance from picking parasites off client fishes. But it seems, at times, they can’t resist easy pickings at the expense of the worms. We have followed the bandits going from worm to worm somehow able to slip inside their open crowns to snap up ensnared bits of food without being detected. 

Last year, Dr. Peter Wirtz shared his paper describing the behavior of a shrimp that steals food from a fan worm (closedly related the the Christmas Tree worm).  The shrimp is practicing kleptoparasitism, that is, food stealing. Though we’ve yet to find any other documentation of the behavior we’ve observed, we’ve always believed the gobies are stealing food from the Christmas Tree worms, in other words, practicing kleptoparasitism. We wrote about it in 2014 in our Critter Hunt column in Scuba Diving magazine and created a short video that was shown on their site for a while. We’ve resurrected it and loaded it here: https://www.youtube.com/watch?v=tieQP218UME

Reference: Wittmann, K.J; Wirtz, P. (2017). Heteromysis sabelliphila sp. nov. (Mysida, Mysidae, Heteromysinae) in facultative association with sabellids from the Cape Verde Islands (subtropical N.E. Atlantic). Crustaceana. 90(2): 131-151.

Note: Portions of this article were originally published in Asian Diver magazine 2006 and in Scuba Diving magazine 2008.

While exploring the pumice plain of Lembeh Strait in northern Sulawesi, Indonesia, I watched a coconut roll down the steep sandy slope of Teluk Kembahu Bay. Even though much of the Strait’s mountainous terrain is fringed with copra plantations, and huskless shell halves commonly litter the seafloor, I had never seen an intact coconut underwater, much less one tumbling along the bottom.

I caught up with the wayward nut as it came to rest at the edge of a sponge bed, picked it up and inspected the brown orb in the palm of my outstretched hand. The overlapping edges of the mismatched halves offered a clue: A Coconut Octopus must live inside! I tested my theory with a tug, and sure enough the two sections, gripped heroically from inside by eight sucker-lined arms, wouldn’t budge. So I set the nut down, backed away and settled in for a wait. I passed the time contemplating the rather fanciful notion that the cephalopod inside just might have intentionally instigated its unorthodox roll down the slope. If so, it would represent an unexpectedly ingenious adaptation for an invertebrate. 

Five minutes later the halves separated slightly and an eye peered out. Eventually the shells opened wide and the occupant appeared in all its Coconut Octopus glory. Then, even more amazing than the maverick coconut, the octopus wrapped six arms around its body and walked away on its two remaining appendages. Although impressed, I naively chalked up the curious behavior to a chance happening and put it out of my mind.

Not a week after returning to the States, National Public Radio broadcast an interview with Dr. Crissy Huffard, then a graduate student at University of California, Berkeley who had recently documented the first bipedal walking behavior in octopuses in the March 2005 issue of Science. By coincidence, her paper described the same behavior by the same species, Amphioctopus marginatus, that we observed in Indonesia. 

Making the news item even more interesting, her colleagues at the university investigating applications for soft robotics took a keen interest in how the octopus was able to pull off this two-legged feat. Basing her study on a short video captured by National Geographic filmmaker Bob Cranston, Ms. Huffard offered her finding: The octopus used the outer halves of its two back arms like tank treads, alternately laying down a sucker edge and rolling it along the bottom, while tightly wrapping the remaining six arms around their bodies. She speculated at the time that the animals employ the behavior to mimic a coconut while they make their escape from predators, or, in my case, a pesky diver.

Unlike most of their relatives that live and hunt around reefs with plenty of hiding holes, Coconut and other sand-dwelling octopuses bury beneath the sand to avoid predators. As added protection, these eight-armed sand dwellers historically utilize abandoned bivalve shells to encapsulate their bodies while beneath the surface. More than likely, at some point after copra plantations proliferated in the region, octopuses began taking advantage of the unusual abundance of processed shell halves.

During times when bivalve shells and coconut halves are in short supply the animals, especially younger individuals, resort to natural and artificial litter, such as shell fragments, glass shards, shoe soles, plastic containers and even toothbrush handles, to cover their bodies. Occasionally when our observations became too intrusive, an octopus would clasp its coconut or bivalve halves to its sides and stride away on extended arms, in a behavior dubbed stilt-walking. The animal’s utilization of random materials and transporting them for later use has been asserted by a group of Australian scientists to be the first documented utilization of tools by an invertebrate.

On our very first dive in Lembeh the following summer, we chanced upon a coconut octopus no larger than a golf ball, squeezed inside the neck of a beer bottle. Like a beckoned genie, the little fellow popped out of the opening and instantly changed from a golden hue into deep reddish brown to better match the dark bottom. Fearing that it was about to bolt, Anna and I eased back. The retreat worked; the octopus slipped Houdinilike back into the bottle and assumed its original complexion. Finding shelter inside discarded bottles and plastic containers is common practice for small recently settled Coconut Octopus. As they mature the youngsters begin cobbling together starter homes from an assortment bottom trash. It’s only later with size that they graduate to coconut halves and large bivalve shells.

Our run of octopus luck continued with the discovery of two large individuals that, although seeming to be at perpetual odds, chose to hang around together. When we first approached, the larger of the pair jumped out of its big, impressive matching bivalve shells, accented with a large piece of green glass and charged its partner forcing it to abandon its modest collection of shell fragments, a toothbrush handle, and a flattened tin can. The assailant rifled through the material and at length commandeered the flattened can. Perturbed into action, the smaller octopus approached the culprit. Undaunted, the can thief stretched its body to an unimaginable height, and with a flash of chromatophores turned the left side of its dark body white. The message was sufficient to send the aggrieved party slinking back to what remained of its burgled home. 

The following morning, we found the thief still in possession of the can. Its companion had replaced the purloined piece with a flip-flop strap. When Anna and I returned in the afternoon, both homes were empty. Following a brief reconnaissance, the twosome was found foraging a short distance away. The pair seemed so intent on the hunt that they paid us little attention.

After trailing them for a bit, their primary hunting strategy became clear: On approaching a small algae or sponge thicket outstretched arms searched the clump. If a tasty morsel, such as a crab or shrimp, was detected a tent of tentacles was thrown over the bush as probing arm tips chased the crustacean into the waiting umbrella of arms.

Almost an hour into our dive, the smaller octopus abruptly buried itself up to its eyes. Once it emerged, its partner galloped over and pounced, enshrouding its sidekick’s body, except for a lone eye that stared out from the entangling arms. As quick as the scuffle began it ended with the antagonist’s departure. The smaller octopus, as if triumphant, raised its body high on a pedestal of arms and remained as still as a statue. With no idea what was happening, I waited and watched for 10 minutes before the encircling arms were drawn back like curtains on a stage, revealing empty bivalve shells—all that remained of a hard-won dinner

Here’s a video from our BlennyWatcher YouTube channel that was originally created for the magazine article in 2006: https://www.youtube.com/watch?v=bmNQXGN_1AA

References: Underwater Bipedal Locomotion by Octopuses in Disguise Christine L. Huffard, Farnis Boneka and Robert J. Full Science 307 (5717), 1927 

“Defensive tool use in a coconut-carrying octopus.” By Julian K. Finn, Tom Tregenza and Mark D. Norman. Current Biology, Vol. 19 No. 23, December 15, 2009

One of our favorite suggestions for fish watchers in the Caribbean is to look for small one-to four-inch Slender Filefish, Monacanthus tuckeri, hiding out within gorgonian bushes, where they shelter from predators, feed, and even more delightful, sleep or rest at night by biting down on polyps for stability – especially helpful when the current runs. This behavior turns out to be a common family trait. In the Caribbean, we have also observed the Whitespotted Filefish, Cantherhines macrocerus,  Orangespotted Filefish, C. pullus, and the Scrawled Filefish, Aluterus scriptus, holding on with their mouths while tucked into the reef. In the Indo-Pacific, we’ve seen Bristle-tailed and Strapweed Filefishes exhibit the same behavior. It appears that filefishes adopt this behavior early in their life cycle – long before they settle onto the reef: 

Blackwater diving has become increasingly popular over the past five years, and social media has given us unprecedented opportunities to see what our fellow divers are observing while drifting at night in offshore waters around the world. A few years back, I noticed the first of many blackwater images of filefishes holding onto things, mostly jellies. Some looked quite young, like the one taken by Deb Devers, of a filefish holding onto a coral polyp. In others, such as the photo by Songda “Wowie” Cai, the filefish appears to be much older. When the image by our friend Nicola Kundrun popped onto my screen two weeks ago, things became even more interesting. This filefish in her image was holding onto a seahorse! Nikki admits she thought she was photographing a filefish latched onto a piece of sea grass but after downloading the photo, her sprig of grass turned out to be a seahorse. 

While we haven’t personally seen anything as entertaining as a filefish hitchhiking on a seahorse, we did capture photos and video of a tiny filefish holding onto a jelly during a night drift in Balayan Bay, Philippines, this past February:

https://www.youtube.com/watch?v=4Z8cRQUcgnY

For me, this was coming full circle from an earlier observation that really intrigued me. In 2008, we published a magazine article and video about the Slender Filefish sleeping on the reef while holding onto a gorgonian polyp. After observing other filefishes in both the Caribbean and the Indo-Pacific doing the same, we updated the video and wrote a 2012 blog post here on BlennyWatcher. After reading our post, Gal Eyal, sent me a paper published in Coral Reefs, documenting what he calls “Teeth-anchorage” in sleeping filefish in the Red Sea. It was the first time we heard of an official name for the behavior. Hunting online, I found a paper written in 1998 by Jeff Childs, documenting what he calls “nocturnal mooring and parking behavior” involving several species of filefishes in the Gulf of Mexico. His paper describes two “sleeping” behaviors – one, holding on with their mouths, and the other, parking themselves in places, out of the current, on the oil platform where he was diving.

Aquarists have long been aware of their filefishes sleeping by holding onto something with their mouths or wedging themselves behind structures in the tank. During a night dive in Indonesia, we saw one species, Pseudaluttarius nasicornis, using its file to lock into a sponge. There was a strong current and this was on a muck site in Lembeh Strait, without a nearby reef, so the filefish tucked itself into a sponge, deploying what Childs calls “parking behavior”.

One of the many joys of fish watching is seeing something for the very first time. It might be a new fish for your life list or a behavior you’ve never noticed before. But one of my greatest pleasures is observing something I’d once read or heard about, with the hope of one day seeing it for myself . “Knowing that something exists” – is one of Ned’s cardinal tips for successful underwater hunting.

In the early 90s, I made a point of reading Dee Scarr’s “What’s That” columns in each issue of Dive Training magazine. I always made a mental note of the wonderful things she wrote about. The closing paragraph in her October 1995 “Fantastic Filefish” article recounted finding a sleeping filefish, “I looked more closely and realized that the filefish had a bit (a polyp, perhaps) of the gorgonian in its mouth. The fish was clearly sleeping, not in the midst of a nibble. It must have grabbed the gorgonian to keep itself in position overnight!” 

Note to self: look for sleeping filefish.

I wasn’t much into diving after dark until about 2005 (that’s a story for another time) so it was nearly a decade after reading Dee’s article, on a night dive in Bonaire, before I saw my sleeping filefish. I was actually attempting to show a cryptic needle shrimp to a friend, when the gently swaying filefish caught my eye. Dee’s description, filed away for over ten years, popped into mind. And sure enough, leaning close we could see the slumbering Slender Filefish had its tiny fish mouth firmly clamped onto a gorgonian polyp!

We spent the next few night dives inspecting every gorgonian we passed, and as often happens, found what we once thought a novel behavior, more common than imagined. In a two-night survey fanning through every gorgonian on Buddy Dive’s house reef, we located a dozen sleeping fish.Fortunately, our night lights didn’t seem to disturb their rest. And best yet, every fish could be counted on to be in the same location night after night, which made sharing the discovery with others a dream. “In the Grip of Sleep” our filefish article published in the February 2008 issue of Scuba Diving magazine added fun and knowledge to Dee’s legacy.

References: “What’s That : Fantastic Filefish “ by Dee Scarr, October 1995, Excerpt, courtesy of Dive Training magazine

Childs, J. 1998. Nocturnal Mooring and Parking Behavior of Three Monacanthids (Filefishes) at an Offshore Production Platform in the Northwestern Gulf of Mexico. Gulf of Mexico Science 16 (2).

“In the Grip of Sleep”  Ned and Anna DeLoach with Paul Humann, Scuba Diving, February 2008  Youtube: https://youtu.be/xcJ3IxUOvS0 and https://youtu.be/WxhGkuI9JxQ

Eyal, G., Eyal-Shaham, L. & Loya, Y. “Teeth-anchorage”: sleeping behavior of a Red Sea filefish on a branching coral. Coral Reefs 30, 707 (2011). https://doi.org/10.1007/s00338-011-0766-y

Adams, Reid & Adams, Ginny & Hoover, Jan & Armbruster, J.. (2003). Oral Grasping: A Distinctive Behavior of Cyprinids for Maintaining Station in Flowing Water. Copeia. 2003. 851-857. 10.1643/i202-261.1. 

“Those Fabulous Filefish!” Scott Michael, Tropical Fish Hobbyist, Sept/Oct 2015