Wiley-Online-Library: Fisheries Management and Ecology: Table of Contents

Estimating Total Post‐Release Mortality in a Boat‐Based Recreational Fishery

Tue, 09 Jun 2026 23:37:16 -0700

ABSTRACT

Catch-and-release angling is widespread in marine recreational fisheries resulting from the implementation of enforced minimum legal sizes and increasing uptake of voluntary release. This makes recreational fisheries selective, with high release rates in certain cases. We estimated the post-release mortality of the boat-based recreational snapper fishery in northeastern New Zealand by characterising catch-and-release practices on private and charter boats, collecting data on fish length, depth of capture, anatomical hooking location and whether the fish was kept or released. Combining this data with harvest estimates from national diary surveys, a length-weight regression and published mortality probabilities based on depth and hooking location, we estimated annual release mortality at 200 t (95% CI [194, 216]) for private boats and 48 t (95% CI [43, 51]) for charter boats. Despite this level of post-release mortality representing 22% of recreational snapper releases, a recent assessment showed the stock to be in a favourable state.

Examining the Impact of Derelict Pots on Blue Crab (Callinectes sapidus) Catch and Harvest Within a Recreational Fishery

Fri, 05 Jun 2026 02:59:30 -0700

ABSTRACT

Derelict fishing gear can negatively affect marine ecosystems through mortality in coastal environments. This study explored the impact of derelict and active crab pots on recreational blue crab (Callinectes sapidus) catch rates and landings in a Mid-Atlantic estuary by deploying experimental pots in four habitat strata within three sections of Indian River Bay, DE. The observed environmental covariates, including temperature, salinity, and dissolved oxygen, varied significantly among areas within individual years (p < 0.001; Kruskal–Wallis). However, the presence of derelict pots did not significantly affect catch rates (p > 0.05; Linear-Mixed-Model [LMM]) despite generally higher numbers of crabs observed in habitats devoid of derelict pots when compared to habitats with derelict pots present. Instead, total catch rates were significantly affected by the presence of ovigerous and non-ovigerous females (p < 0.001; LMM). Carapace widths showed no significant variation (p = 0.80; Kruskal–Wallis), suggesting consistent length distributions in 2021 and 2022. Eight bycatch species were captured. Findings suggest that derelict pots did not significantly affect catch rates, differing from observations in other systems, for example, Chesapeake Bay. Further explorations along a broader range of environmental conditions are needed to clarify these dynamics.

Recovery of Four Commercial Fish Stocks in Lake IJsselmeer (The Netherlands) After Major Fishery Management Interventions

Joey J. J. Volwater, Justin C. Tiano, Kelly Chin, Joep J. de Leeuw — Thu, 04 Jun 2026 21:03:19 -0700

ABSTRACT

Sustainable management of inland fisheries presents major challenges because it often involves complex and open access systems. Lake IJsselmeer is among the largest freshwater lakes in western Europe and supports active commercial fisheries. By 2012, excessive fishing effort had reduced the stocks of four key resident species: pikeperch (Sander lucioperca), perch (Perca fluviatilis), roach (Rutilus rutilus), and bream (Abramis brama) to historically low levels as indicated by both survey indices and commercial landings. In response, the Dutch government implemented major fishery management interventions in 2014: (I) reductions to gillnet fishing (15% of the available effort) and (II) previously unregulated seine fisheries targeting bream were limited from 135 to 7 days per year per license. To evaluate the impact of these management measures, time-series analysis of spawning stock indices and population structures were performed. Our analysis, also including environmental changes in water temperature and phosphate levels, reveals that these major regulatory interventions were the primary driver of stock recovery, successfully halting declines in all four focal stocks and enabling the increase of both fish populations and commercial catches. The pikeperch population has shown a particularly sharp and sustained stock recovery, while increases in length-based indicators in all four stocks suggest broader recovery patterns. This case study demonstrates how targeted regulatory measures can effectively reverse stock declines and support the recovery of fish populations in heavily exploited freshwater systems.

Identification and Characterization of Antarctic Krill (Euphausia superba; Dana 1850) Fishing Grounds Using Commercial Vessel Data From the Antarctic Peninsula and South Orkney Islands

Gabriela Torretti, Luis A. Cubillos, Francisco Santa Cruz — Wed, 03 Jun 2026 22:15:46 -0700

ABSTRACT

The Antarctic krill (Euphausia superba) fishery is primarily concentrated around the major island groups and shelf-break regions of the West Antarctic Peninsula and South Orkney Islands. Climate-induced sea ice retreat has recently expanded fishing access to previously inaccessible areas, thereby altering spatial and temporal patterns of fishing activity. Because krill distribution and aggregability strongly influence where vessels operate, it is critical to identify specific areas that are repeatedly used as fishing grounds. In this study, we analyzed haul-by-haul fishing data from the Chilean vessel Antarctic Endeavour 2017–2024 to identify spatial and temporal clusters of fishing activity. Following the concept of fishing opportunities (FOs), we used hierarchical agglomerative clustering to delineate recurrent, sporadic, and unusual FOs. This procedure resulted in 27 FOs, seven of which were used consistently across years and therefore considered recurrent fishing, comprising 951 hauls. Multivariate correspondence analysis revealed distinct groupings of bycatch species composition across FOs. Furthermore, variations in the proportion of gravid females and juveniles helped identify areas relevant to krill reproduction and recruitment. Catch-per-unit effort (catch rate) trends across years indicated stable or declining yields, with evidence of a significant local declining trend in some recurrent FOs. These findings highlight the importance of spatially explicit fishery analyses of fishing behavior and support the development of fine-scale management strategies for Antarctic krill fisheries under rapidly changing environmental conditions.

Linkage Between Sex Ratio and Sea Age Composition of Atlantic Salmon in Scottish Rivers

Wed, 03 Jun 2026 21:59:24 -0700

Fisheries Management and Ecology, EarlyView.

Using Long‐Term Monitoring Data to Assess Temporal Patterns in Fish Community Assemblages in Florida Lakes

Kimberly I. Bonvechio, Andrea Sylvia, Andrew K. Carlson — Wed, 03 Jun 2026 21:20:18 -0700

ABSTRACT

In an effort to increase the relevancy of fish community data for management, we used fish community data to conduct a statewide assessment of Florida's freshwater fisheries resources and compare the relationships between environmental factors and freshwater fish communities over time. Fish community weight and count data were obtained for 21 lakes sampled as part of Florida's Long-Term Monitoring (LTM) program from 2006 to 2021. Results suggest that gamefish and nongamefish assemblages in these lakes can be dynamic, and these differences are related to variables at local (e.g., water depth), lake (e.g., trophic state index), and regional (e.g., annual average daily precipitation) scales. Although some similarities exist among lakes, fish assemblage patterns and their relationships to these variables were often specific to individual lakes or subgroups of lakes, which indicates the challenge of characterizing the status and temporal patterns in fish communities over a large spatial area.

Comparative Studies Are Needed to Contextualize Stranding in Hydropeaking River Systems

Raegan Davis, Steven J. Cooke, Karen E. Smokorowski — Mon, 01 Jun 2026 23:31:33 -0700

Fisheries Management and Ecology, EarlyView.

Variability in Fecundity–Body Size Relationships for Atlantic Salmon Associated With Body Condition and Life History

Thu, 21 May 2026 23:05:40 -0700

ABSTRACT

While body size is the primary driver of fecundity, other factors may contribute to variation in these relationships. Anadromous populations of Atlantic salmon (Salmo salar) have diverse life histories, and fisheries management relies on accurate fecundity estimates. We used Bayesian hierarchical models to determine the relationship between fecundity and fork length, and other life-history characteristics, for 25 spawning populations throughout Eastern Canada. Fecundity was best modeled at the river level, increased with body size and condition, and decreased with mean egg diameter. Fecundity was higher for individuals that spent fewer years in freshwater as juveniles, and for consecutive repeat spawners compared with first-time (or maiden) spawners that spent 1 year in the ocean. Lastly, there was interannual variability in the fecundity–body size relationship. These relationships should be used in conjunction with data on recent changes in body size and/or life-history traits of populations to inform stock management.

Contribution of a Pre‐Processing Phase to Create a Biomass Indicator From Big Data With an Application to the Striped Red‐Mullet in the Bay of Biscay

Thu, 21 May 2026 22:59:28 -0700

ABSTRACT

Biomass indicators derived from fishery-dependent LPUE data are widely used for data-limited stocks. But the influence of data pre-processing on their reliability remains poorly documented. Using Bayonne district fisheries of striped red mullet as a case study, we evaluated how three levels of pre-processing—none, light, and hard—affect data structure, model behavior, and the resulting biomass signal. Although the raw, lightly filtered, and heavily filtered datasets retained broadly similar temporal patterns, pre-processing substantially reduced noise and heterogeneity arising from spatial coverage, fleet composition, and declaration practices. Models fitted to pre-processed datasets showed markedly improved performance, with RMSE reduced by half compared to models using raw LPUE data, and computation time decreasing sharply as filtering increased. Importantly, pre-processing also altered the set of explanatory variables selected by GAMMs, highlighting that data refinement reshapes the ecological and behavioral information embedded in LPUE. Our results demonstrate that pre-processing is not a neutral technical step but a determinant of the biological representativeness, interpretability of LPUE-based indicators, and the frugality of big data models. This study provides a transparent framework for integrating expert knowledge into big-data workflows and for improving the robustness of populations indicators used in data-limited stock assessment.

Site Fidelity, Depth Preference and Vertical Movement Patterns of Lentic and Lotic European Catfish Silurus glanis

Albert Ros, Jan Baer, Matthias Fromherz, Juergen Geist, Alexander Brinker — Thu, 21 May 2026 00:00:00 -0700

ABSTRACT

To study variables that may trigger the dispersion of the currently expanding European catfish in its native distribution limits, 42 individuals were captured from Upper Lake Constance (lentic) and 42 from two streaming tributaries (lotic), fitted with pressure and temperature loggers, and released at the site of capture (control: lotic or lentic) or into a new environment (lotic-to-lentic or lentic-to-lotic). Twenty-seven fish were recaptured within 662 days. Lentic and lotic fish showed similar seasonal vertical migration patterns, descending in winter and ascending in summer to warm shallow water. European catfish descending to the depth of the lotic river-bed decreased in vertical movement activity, whereas lentic European catfish descending to deeper layers in the lake remained active with vertical movements. This may relate to the differences between these habitats in European catfish's hunting and social behaviour. Of control released fish, 14 out of 17 were recaptured near to the original catch site. The remaining three control released fish were lotic fish and had dispersed to the lake (lentic). Of translocated fish, all eight recaptured lentic-to-lotic fish returned to the lake, while the two recaptured lotic-to-lentic translocated fish remained in the lake. The overall higher dispersal towards and retention in the lake suggest the lentic habitat to be strictly favoured over the lotic habitat. The results support quick adaptation of European catfish to a cold-water lake that was few decades ago still mostly unexploited by the species. Conservation and fisheries management should take such fast adaptations in an apex predator into account.

Length‐Based Spawning Potential Ratio Assessment of Key Species From a Remote Recreational Fishery at Diego Garcia, Indian Ocean

Wed, 20 May 2026 03:49:51 -0700

ABSTRACT

Recreational fisheries in remote regions often operate under limited regulation and data availability, presenting challenges for sustainable management. Diego Garcia, located within the Chagos Marine Protected Area, hosts a unique recreational reef fishery embedded within a highly protected environment. We assessed the stock status of five key species—Lutjanus bohar, L. gibbus, L. monostigma, Caranx melampygus, and Variola louti—using the Length-Based Spawning Potential Ratio (LB-SPR) approach and length composition data collected through stereo-video surveys. The average spawning potential ratio (SPR) across all species appears to be operating above 30%, a common threshold below which a stock can be considered overfished. The SPR of L. bohar and L. gibbus remained above 30% across all bootstrap iterations indicating confidence that these species are exploited at a sustainable level. L. monostigma, C. melampygus, and V. louti exhibited greater uncertainty in their estimated SPR, spanning all possible values with at least 50% of bootstrap iterations remaining above 30% SPR; for these species, caution should be applied until additional sampling can improve the resolution of these estimates. These findings suggest that the recreational fishery is operating within sustainable limits, likely due to access restrictions and diffuse fishing pressure across species. However, uncertainty in model outputs for data-limited species underscores the need for continued biological sampling and catch monitoring.

Long‐Term Evaluation of Density and Biomass of Pollicipes pollicipes Along the Basque Coast (N of Spain), and Relation to Wave Energy Changes

Angel Borja, Almudena Fontán, Joxe Mikel Garmendia — Tue, 19 May 2026 21:32:27 -0700

ABSTRACT

The goose barnacle (Pollicipes pollicipes), a valuable intertidal species, is overexploited along the Basque coast, with biomass often far below levels predicted by wave energy models. A 22-year study (2002–2024) shows that while wave energy strongly correlates with barnacle abundance, illegal and unregulated harvesting has led to significant stock depletion. Some recovery has occurred since 2014, likely due to the increasing wave energy received. Comparison with regions like Galicia and Asturias highlights the effectiveness of comanagement systems involving fishers and authorities, with structured exploitation plans, quotas, and monitoring. In contrast, passive management in the Basque Country has proven insufficient. Only a few sites now exceed biomass thresholds. Lessons from Canada and Southwest Europe emphasize that sustainable recovery requires stricter enforcement, rotational harvesting, extended closures, and fisher participation. Without urgent, coordinated action, the long-term viability of goose barnacle populations in the Basque Country remains at risk.

Value and Volatility of Squid as a Fisheries Resource in the North Sea and Adjacent Waters—Starting Point for a Sustainable Management

Erik Sulanke, Ralf Döring, Daniel Oesterwind — Fri, 08 May 2026 00:00:00 -0700

Fisheries Management and Ecology, Volume 33, Issue 3, Page 438-441, June 2026.

Issue Information

Fri, 08 May 2026 00:00:00 -0700

Fisheries Management and Ecology, Volume 33, Issue 3, Page i-iv, June 2026.

Fisheries Management Models in the Mediterranean Sea: An In‐Depth Review

Salma Aboussalam, Karima Khalil, Marta Coll, Zainab Damsiri, Khalid Elkalay — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

This study presents a bibliometric review of fisheries management models in the Mediterranean from 1992 to 2024, with the aim of assessing progress and identifying research gaps. Key countries were analyzed for their contributions, while emerging trends were explored through keyword analysis. The review covered 878 documents, highlighting the variety of models used to assess ecological impacts on Mediterranean fisheries. In particular, the “Assessment for All” (a4a) model emerged as the most widespread, used in 23% of studies, demonstrating its acceptance by researchers. Within the Stock Assessment Models category, a4a was followed by SPiCT and XSA, which were also frequently applied, reflecting their relevance and adaptability in data-limited and data-rich fisheries contexts. In the Ecosystem Models category, Ecopath with Ecosim (EwE) was the most utilized tool, widely applied for representing trophic interactions and evaluating ecosystem-based management scenarios. MaxEnt led in the Species Distribution Models (SDMs) category, valued for its predictive performance using environmental data. Although specific names were often not reported, economic models were also commonly used, indicating the growing incorporation of socio-economic dimensions in fisheries research. ISIS-Fish was the most employed within the Population Dynamics Models, allowing detailed simulation and assessment of the impact of different management strategies on fisheries, fleets and ecosystems. In the Statistical Models category, Generalized Additive Models (GAMs) dominated, appreciated for their flexibility in modeling non-linear relationships. Lastly, the Princeton Ocean Model (POM) was the most frequently used in Hydrodynamic and Biogeochemical Models, highlighting its capacity to simulate physical and ecological marine processes.

Cost Efficiency of Fishing Among Small‐Scale Trawlers in Vietnam: A Stochastic Frontier Analysis

Dang Thi Phuong, Nguyen Thi Kim Quyen, Huynh Viet Khai — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

This study analyzes the cost efficiency of small-scale trawlers in the Mekong Delta, Vietnam, a region where small-scale fisheries are vital for livelihoods but face significant economic pressures. Using primary data collected through surveys and interviews with 223 small-scale trawler operators in four coastal provinces (Soc Trang, Bac Lieu, Ca Mau and Kien Giang) from January 2020 to May 2021, this study applies a stochastic frontier analysis (SFA) to estimate cost efficiency. The translog stochastic frontier cost function, chosen for its flexibility, is employed to analyze the data. Results show that the average cost efficiency of the small-scale trawler fleet in the Mekong Delta was 70.0%. This indicated that, on average, a fishing operation in the study area had the potential to reduce costs by 30.0% to achieve the same level of output, while operating under the existing technology. Factors related to personal and fishery characteristics have varying effects on total costs. The research results revealed strong effects of factors such as vessel size, family member ratio, and fishing ground location, while education, training, and cooperation showed no discernible effects on total costs. The findings suggest that targeted policies such as expanding training programs, improving fixed assets, and increasing awareness of adherence to policies and regulations could significantly enhance the economic sustainability of small-scale trawler operations in Vietnam.

Local Angler Knowledge Reveals Declines in Fishing Quality for Black Bass in Lakes of Eastern Ontario

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Local ecological knowledge can be useful to assess data-limited fisheries such as the Ontario Black Bass (Micropterus spp.) recreational fishery. We surveyed local anglers using the Life History Calendar approach to determine if there were perceived changes in fishing quality for Black Bass in eastern Ontario across different time periods. For both species (Largemouth Bass and Smallmouth Bass), respondents noted declines in numbers and body sizes of their catch across most of the time periods (1975–2025) with sharp declines beginning in 2005. The reported declines were notably consistent across the waterbodies studied and did not differ across different user types (e.g., tournament anglers vs. other anglers). The results of this study show that anglers overwhelmingly perceive that the quality of bass fishing in eastern Ontario has deteriorated over the past few decades, highlighting the (1) utility of using local angler knowledge to complement traditional stock assessment methods and (2) the need to consider alternative monitoring and management strategies to reverse those declines.

An Essential Estimation for Effective Fishery Management of the California Market Squid Doryteuthis opalescens (Berry, 1911)

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Fishery sustainability and profits are achieved through adequate fishery management, for which parameters should be assessed using assertive approaches. Thus, we analyzed dorsal mantle length and age data of the California market squid (Doryteuthis opalescens) by the multi-model inference approach to describe its growth pattern based on model performance. Two asymptotic and four non-asymptotic growth models were candidates for our data set. In contrast with the growth pattern previously assumed for Doryteuthis opalescens (non-asymptotic), our results show clear evidence that the species follows an asymptotic growth pattern. The best candidate growth model was Gompertz with L _∞ = 233.71 mm DML (CI 232.26–235.24 mm DML, p < 0.05), t0 = 152.69 (CI 148.87–156.12, p < 0.05), and k = 0.0125 (CI 0.0113–0.0143, p < 0.05). With this essential estimation, the type of growth of the California market squid was defined, and size-at-age data of this species is now available for fishery management.

Marketing Strategy‐Based Fishers' Segmentation: The Key to Sustainable Fisheries Sector

Eleni Kaimakoudi, Angelos Liontakis, Stamatis Mantziaris, Irene Tzouramani — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

This paper attempts to empirically investigate potentially significant differences in perceptions regarding marketing strategies that could enhance economic and environmental sustainability in the sector based on the Structure—Conduct and Performance (SCP) methodological framework. Quantitative data were gathered through personal interviews with fishers around Greece, including both small-scale (SSF) and large-scale (LSF) fisheries. A combination of exploratory factor analysis, cluster analysis, and discriminant analysis was employed to identify potentially distinct groups among fishers. Chi-square tests were employed to examine possible relationships between fishers' willingness for training and funding and cluster membership. Two heterogeneous segments were derived. They were labeled Lowly Innovative and Highly Innovative. The results demonstrate that there are statistically significant differences between the two distinct clusters regarding the adoption of strategic marketing management decisions. The outcomes highlight the requirement of targeted marketing strategies, funding for selective fishing gears, and training programs for sustainable development in the sector.

Revisiting Maturity Data: Using Oocyte Diameter and Gonadosomatic Index to Retroactively Apply a New Maturity Scale to Greenland Halibut (Reinhardtius hippoglossoides)

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Greenland halibut (Reinhardtius hippoglossoides) is a deep-water flatfish which lives at temperatures of 1°C–4°C and produces large eggs (> 3 mm). The combination of low temperatures and large eggs has resulted in an unusual ovary development cycle, with vitellogenesis taking more than 1 year. This means that fish with early vitellogenic oocytes (termed functionally immature) will not spawn during the next spawning season and should not be included in the Spawning Stock Biomass (SSB). During the Icelandic autumn groundfish survey, the ovary development of Greenland halibut has been evaluated using a 4-stage maturity scale. The 4-stage scale, unlike the 6-stage scale developed specifically for Greenland halibut, does not separate fish in the first year and second year of vitellogenesis which can lead to inaccuracies in the estimation of SSB. The current study investigates whether the weight of the gonad, expressed as a percentage of total body weight, commonly known as gonadosomatic index (GSI), can be used to evaluate maturity for Greenland halibut. We show, from measurements of oocytes, for Greenland halibut collected in Iceland and East Greenland, 93% of Greenland halibut with a gonadosomatic index (GSI) > 1.5% are in their second year of vitellogenesis and should be considered sexually mature. In addition, 97% of fish with a GSI < 1.5% were considered sexually immature/functionally immature. Application of this GSI-based approach to data collected during the Icelandic autumn groundfish survey demonstrates that it is a practical alternative to visually assessing maturity and can be retroactively applied to past data if gonad weight has been measured. Using GSI to discriminate sexually mature from sexually immature/functionally immature individuals resulted in a length at 50% maturity (L ₅₀) 2.4–8.8 cm higher in comparison to visually assessing maturity with the 4-point scale. The GSI-based approach indicated that fish visually classified as ‘spent’ were misidentified and are a mix of other maturity stages, this is supported by the spawning season being 7–9 months prior to the survey. Our data indicates that L ₅₀ of Greenland halibut in Iceland increased in 2012, with L ₅₀ in the period 1996–2010 approximately 73–77 cm whereas in the period 2012–2023 it was approximately 78–81 cm. While, for years 2014–2023, when age was estimated, age at 50% maturity (A ₅₀) was 18.2 years.

Understanding Consumptive Orientations in Rock Fishing: A Taiwanese Case Study for Sustainable Fisheries

Hui‐Chiao Wang, Ting‐Yu Liao, Chien‐Hsing Wu — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

This study adapts and validates the Consumptive Orientation Scale (COS) for licensed rock anglers at Keelung Islet, Taiwan, to clarify attitudinal structures relevant to sustainable recreational fisheries management. An SMS-distributed, web-based survey was sent to the official roster of licensed rock anglers (4036 invitees); 651 usable responses were obtained (16.1%). Confirmatory factor analysis supported a four-factor, 13-item solution with good fit and acceptable internal consistency. Inter-factor correlations indicated related yet distinct attitudes: Catching Something correlated positively with Catching Numbers of Fish and with Retaining Fish; Catching Numbers of Fish correlated positively with Catching Large/Trophy Gamefish; and Catching Large/Trophy Gamefish correlated negatively with Retaining Fish, while the association between Catching Numbers of Fish and Retaining Fish was weak and non-significant. These patterns delineate heterogeneous attitudinal profiles without inferring observed handling outcomes, consistent with cross-cultural validation studies of COS in other angling contexts. The validated instrument strengthens the theoretical linkage between consumptive orientation and the human dimensions of fisheries, enabling tracking of attitudinal segments over time. Findings also inform adaptive communication and policy strategies for emerging recreational fisheries in East Asia, where angler-focused conservation norms are still developing.

Visual Modelling to Predict Behavioural Responses of Catsharks, Skates, and Plaice to Artificial Light for Use in Bycatch Reduction

Jasmine Somerville, Jon Blount, Martin Stevens — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Light can be used to deter bycatch from fishing nets, but few studies have aimed to quantify how species view and respond to light. Here, we used visual models to predict how target (plaice Pleuronectes platessa) and bycatch (small-spotted catshark Scyliorhinus canicular and undersized skates, Raja spp) species, captured in mixed demersal fisheries, responded to light-emitting diodes (LEDs) in tanks. Models predicted that behavioural responses were linked to the likely visibility of LEDs to catsharks. Specifically, catsharks interacted more with LEDs that were apparently more stimulating to their vision (white, green, blue). In contrast, skates and plaice were less responsive to light. Potential responses of species to light could be inferred from visual models, but differences in ecology translated into differences in behaviour towards light. Our modelling approach could help to select an optimal light colour for future bycatch-reduction trials.

Morphometric and External Injury Characterization of Rainbow Trout (O. mykiss) Used for Stocking in the Alpine River Inn (Bavaria, Germany)

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Stocking fish is a common practice in fisheries management, particularly for species of high conservation value or economic importance. Despite its widespread use, systematic evaluation of fish stockings remains scarce. This includes non-native species such as rainbow trout (Oncorhynchus mykiss), which are intensively stocked into European water bodies for recreational angling. Rainbow trout used for stocking into the German River Inn are sourced from various hatcheries, likely contributing to differences in their physical condition which may affect post-stocking survival. This study provides a baseline assessment of the physical condition, focusing on morphometric traits and external injuries, of rainbow trout prior to stocking in this large alpine river. We analyzed 150 individuals from five aquaculture facilities using morphometric measurements and standardized injury assessment protocols. Rainbow trout showed a high level of morphometric plasticity associated with their origin. All examined fish had visible external injuries, with the most frequent ones being tears and amputations on the caudal and dorsal fins, as well as scale loss. Up to 11 of 22 possible injury types were identified in the most severely affected individuals, and specific external injury patterns could be related to specific hatcheries. These findings offer important baseline data on the physical condition of stocked rainbow trout and provide a foundation for interpreting future studies on their performance in the wild.

Stock Rebuilding in a Mixed‐Population Fishery Context: The Case of North Sea and Western Baltic Herring

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Managing and giving advice for mixed-population fisheries of the same species can be challenging due to difficulties in predicting stock mixing, technical interactions, and in ensuring precautionary stock dynamics. Most fish species consist of several populations all of which need to be sustainably managed to preserve biodiversity and resilience to environmental changes, and to sustain productive fisheries. Mixing of populations of the same species with different productivity represents additional challenges for assessment and management. In such cases, there is a need to develop assessment and advice methods to consider mixed stocks and advise managers on fishing opportunities. In this study, we develop a framework including multifleet multi-stock assessment models and forecasts where future stock dynamics depend on stock mixing, fleet-specific fishing opportunities, and management in place. This framework is applied to the large North Sea herring stock and the overexploited western Baltic herring stock, which in part of their distribution areas are found to be mixed in both catches and surveys. The framework is used to investigate the trade-offs between stock rebuilding and fishing opportunities in a mixed fishery. The study shows that spatial management implying transfer of quotas away from the areas where the stocks mix and towards the stock in good condition could help stock rebuilding without reducing overall fishing opportunities, however with a slower rebuilding rate compared to a more drastic fishery closure. The implementation of quota transfer should however consider the spatial relocation of fishing opportunities to avoid catch advice overshoot and inflated quotas.

Evaluating and Advancing the Use of Shore‐Based Observers for Scientific Sampling and Catch Verification in High‐Volume Fisheries

Christian Gredzens, Andy Kingham, Jason E. Jannot — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Shore-based observers are increasingly being used in place of at-sea observers to monitor and sample commercial fisheries catch. However, few evaluations assess whether these programs meet their stated goals or how to optimize them, and industry data are rarely tested for accuracy despite serving as the foundation for catch accounting. Using a high-volume trawl fishery as a case study, we evaluated observer performance, assessed the accuracy of industry data, and present a transferrable framework for evaluating observer performance and optimizing sampling. Observers performed well under expanded duties, meeting high-priority objectives, nearly meeting secondary goals, and detected species at low catch fractions (~0.7%). Comparisons with industry data revealed under-reporting or aggregation for some managed species, underscoring the need for independent verification. Results highlight that shore-based observers can fulfill expanded duties, maintain core functions, and provide critical checks on industry-reported data. The framework employed here is applicable to other programs seeking to evaluate and optimize shore-based monitoring programs.

Assessing Bycatch Vulnerability in Hilsa Gillnet Fishing Along the Southeastern Coast of Bangladesh Using Productivity and Susceptibility Analysis (PSA)

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Hilsa the cornerstone of Bangladesh's marine fishing industry contributes significantly to the national economy through providing food, nutrition, employment and foreign exchange. In Bangladesh the primary method for capturing Hilsa revolves around the widespread use of gillnets. However, the extensive use of gillnets give rise to concerns about potential negative impact, particularly in terms of bycatch. Therefore, this study employed a data-poor method, productivity and susceptibility Analysis (PSA) to evaluate the bycatch vulnerability in gillnets of 15 commercially important fish species from the coast of Bangladesh, including Hilsa. These species were selected through an extensive questionnaire survey along the coast of Chattogram and Cox's Bazar district. The result indicates that Lepturacanthus savala had the lowest productivity value, scoring 1.30. Given that Hilsa is the primary target species for gillnet fishing, it exhibited the highest susceptibility score of 2.92. Among the 15 species four species Tenualosa ilisha, Eleutheronema tetradactylum, Lates calcarifer, Polynemus paradiseus also showed elevated susceptibility with score of 2.92, 2.43, 2.47 and 2.83 respectively. Species with low productivity and high susceptibility exhibited comparatively higher vulnerability scores. Among all the species analyzed about 79.37% showed a moderate level of risk, 8.07% indicated low risk and 18.59% were classified as having a high risk of bycatch in gillnet. Lates calcarifer and polynemus paradiseus showed higher risk of being bycatch in gillnets with vulnerability score of 2.03 and 2.00 respectively. Conversely, Coilia dussumieri had the lowest risk with a vulnerability score of 0.85. Though PSA is characterized by several limitations, including the unavailability of species-specific life-history and susceptibility data, reliance on proxy values, and inherent subjectivity, this approach offers a transparent and precautionary framework for assessing species vulnerability in data-poor fisheries and serves as a rapid screening tool to inform management priorities. Therefore, this study emphasizes the necessity of improving data collection on species-specific life-history traits to enhance the accuracy and reliability of vulnerability assessments.

Institutionalizing Indonesia's Commercial Fisheries: Insights From Fleet Dynamics and Vessel Monitoring Systems

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Despite decades of investment in monitoring, control, and surveillance (MCS), Indonesia's commercial fisheries management remains hindered by weak integration of monitoring outputs into policy processes. Persistent expansion of commercial fleets—both domestically and into transboundary waters—reflects systemic gaps in governance, compounded by fragmented and inconsistent fisheries data. This study applies a rapid assessment framework that combines community-based knowledge, vessel monitoring technologies, and secondary data sources. Analytical methods include social–ecological network analysis, principal component analysis, self-organizing maps, and geographic information systems (GIS), with spatial data overlays used to qualitatively infer decision-making opportunities. The findings reveal pronounced differentiation between industrial-oriented and community-based fisheries, alongside a gradual, unregulated shift of traditional fishers into commercial operations. Scientific research uptake remains limited, and socio-economic disparities between capital owners and fishing crews persist. Current management priorities are disproportionately focused on small-scale fisheries, while the industrial-commercial sector operates with minimal strategic oversight. Moreover, policy approaches tend to apply uniform regulations across disparate fishery types, undermining adaptive responses. We propose the establishment of a specialized governance authority for integrated, scale-sensitive management of both industrial-commercial and community-based fisheries, underpinned by adaptive, evidence-driven, and socially inclusive policy frameworks.

Advancing High‐Seas Fisheries Governance: Bayesian Models for Enhancing Compliance and Sustainability Under the BBNJ Agreement

Ahmed Hany M. Abuelenin — Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

High-seas fisheries governance faces significant challenges due to transboundary complexities, enforcement limitations, and scientific uncertainties. The recently adopted Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Agreement) represents a pivotal legal framework aimed at strengthening regulatory mechanisms. This study explores how Bayesian methodologies can enhance high-seas fisheries governance by improving stock assessments, quota allocations, and compliance monitoring. Bayesian inference offers a probabilistic approach to decision-making, integrating prior knowledge with real-time data to optimize policy predictability and adaptive management. Through a case study approach, this research assesses the practical applicability of Bayesian models under the BBNJ framework, highlighting their potential to address legal and enforcement gaps while ensuring sustainability. The findings contribute to both legal and fisheries management scholarship, offering data-driven recommendations for policymakers to enhance science-based governance in areas beyond national jurisdiction.

Factors Influencing the Stocking of Juvenile Pikeperch (Sander lucioperca)

Fri, 08 May 2026 00:00:00 -0700

ABSTRACT

Predator species of fish play crucial roles in ecosystem balance through top-down control, a mechanism frequently exploited in biomanipulation to stock predator species. Juvenile pikeperch (Sander lucioperca) were stocked (n = 52,887) in spring 2023 and 2024 and autumn 2023 to compare stocking efficiency between Recirculation Aquaculture Systems (RAS) and pond culture systems. Post-stocking mortality was high and differed among rearing methods and stocking seasons (pond-reared: 93.3% in spring 2023, 100% in autumn 2023, and 98.9% in spring 2024; RAS-reared: 100% in spring 2023, 99.5% in autumn 2023, and 99.1% in spring 2024). Recapture rates of pond-reared pikeperch stocked in spring 2023 were highest, despite being smaller than corresponding RAS-reared pikeperch when stocked. Recapture rates of autumn-stocked pikeperch were low for both rearing methods in the single release of 2023. Pond-reared pikeperch were smaller when stocked (91.56 mm in spring 2023; 69.26 mm in spring 2024) but grew faster and often reached a similar size as RAS-reared fish that were larger when stocked (139.40 mm in spring 2023; 162.80 mm in spring 2024). When recaptured in spring 2023, both groups reached a similar size (~183 mm; at recapture in spring 2024 they had nearly similar sizes pond: 169 mm, RAS: 197.25 mm). Overall, survival of pond-reared pikeperch was significantly higher than RAS-reared fish, even after accounting for size at stocking and season. Rearing system, rather than initial size alone, strongly influenced post-stocking success. High density of adult European perch (Perca fluviatilis) preyed heavily on juvenile pikeperch, thereby limiting natural recruitment. For pond-reared pikeperch, size was crucial due to limited energy reserves for overwintering, whereas RAS-reared pikeperch were challenged by a delayed shift to natural prey, poor shelter-seeking behavior, and predator naïveté. Overall, we found that stocking success depended on factors beyond size at stocking, and high mortality prevented stocking alone from achieving desired ecosystem management goals.

Sex‐Specific Atlantic Salmon Upstream Passage and Fallback at a Natural Cascade After Dam Removal

Mon, 04 May 2026 21:56:28 -0700

ABSTRACT

In the Boquet River (NY, USA) a low-head dam set above a ~200-m bedrock cascade was removed in 2015. We used radio-telemetry to assess landlocked Atlantic salmon passage at the remaining cascade (2020, 2022). Across years, 52% of males (13/25) attempted cascade passage whereas females made no discernable attempts (0/11). Attempt probability increased with stream discharge and decreased with fish size, though overall passage success was low (1/36). Shallow depths—likely owing to an artificially widened channel—appear to be limiting passage. Additionally, we transported fish upstream but observed high fallback (72%) that was associated with fish size and energetic status. Following dam removal, this cascade continues to limit upstream passage resulting in increased vulnerability to angling during migratory delay. Overall, we highlight the importance of follow-up studies after dam removal, and that further modifications at this site may be required to improve passage.

RESUMEN

En 2015 fue demolida/eliminada una pequeña presa construida encima de una cascada sobre lecho de roca de ~200 m longitud. Usamos radio-telemetría durante 2020 y 2022 para evaluar el paso de salmón atlántico a través de la cascada resultante por la eliminación de la presa. Durante los dos años de la investigación, el 52% de los machos de salmón (13/25) intentaron pasar, mientras que las hembras no hicieron intentos discernibles (0/11). La probabilidad de intentos aumentó con el caudal del río y disminuyó con el tamaño de los peces; sin embargo, en general, el éxito fue bajo (1/36). Parece que la poca profundidad—quizás creada por el ensanche artificial del río—limitó la capacidad de paso. Además, también transportamos salmones aguas arriba de la cascada, pero observamos altos niveles de retroceso (72%), que fueron asociados al tamaño y estado energético de los peces. Después de eliminar/demoler la presa, este sitio sigue limitando el movimiento aguas arriba, incrementando la vulnerabilidad de captura por pescadores durante el retraso migratorio causado por la barrera. En general, esta investigación resalta la importancia de hacer investigaciones después de la eliminación de presas, y que son necesarias modificaciones adicionales en este sitio para mejorar el pasaje de los peces.

The Effects of Nutrient Additions on Kokanee in Dworshak Reservoir, Idaho

Fri, 24 Apr 2026 00:00:00 -0700

ABSTRACT

We investigated the effects of whole reservoir nitrogen (N) addition on kokanee growth in Dworshak Reservoir, Idaho. We hypothesized that N addition would improve the growth of kokanee (Oncorhynchus nerka) at a given level of abundance by increasing the availability of Daphnia, an important food source. Age-specific size (length, weight, and relative weight) and biomass were compared for periods with and without N addition. Mixed effects models were used to determine the relative importance of N addition, kokanee abundance, Daphnia availability, reservoir inflow, and temperature on annual growth. Simple linear models were used to assess how the importance of these variables changed with age. Kokanee were longer, heavier, and more abundant during periods with N addition, leading to a 56% increase in mean biomass. Age-specific abundance was the most important factor influencing the growth of age-0 kokanee. Daphnia availability replaced age-specific abundance as the most important factor for age-1 kokanee and increased in importance for age-2 kokanee. While Daphnia biomass was the proximal driver of kokanee growth, N addition was previously found to increase Daphnia biomass given kokanee abundance. Therefore, N addition may be a useful tool to mitigate for density-dependent growth or lost productivity in N limited systems.

Use and Trust of Digital and Traditional Media Among Recreational Anglers in Germany: Findings From a Nationwide Survey

Wolf‐Christian Lewin, Marc Simon Weltersbach, Harry V. Strehlow — Tue, 21 Apr 2026 00:00:00 -0700

ABSTRACT

Data on recreational fisheries are often limited, and scientists increasingly use digital platforms to collect information otherwise difficult to obtain. Using telephone-diary survey data, this study examines angling-related media use (face-to-face communication, angling magazines, TV or radio, YouTube, messenger services, social media, other angling-related websites, and angling apps) and trust in these sources among German anglers. Personal face-to-face communication, YouTube, and angling magazines were the most frequently used sources for information. Many participants rarely or never used digital platforms. Approximately 53% of participants used YouTube occasionally, often, or regularly, compared to 15% who used angling apps in the same way. Trust in digital sources was low: 11% rated social media such as Facebook and X, and 25% rated angling apps quite or very trustworthy. Digital media use was positively related to angling centrality and negatively to age. These findings highlight the need for further research on motivators and barriers affecting anglers' engagement with digital platforms.

Lack of Compliance in Gillnet Fisheries Regulations Increases Risk to a Vulnerable Species

Sun, 12 Apr 2026 00:00:00 -0700

ABSTRACT

This article presents an analysis of regulatory compliance in a Brazilian gillnet fishery, based on Vessel Monitoring System (VMS) tracking data. Satellite transmissions records, interpreted as proxies for gillnet haulings events, were analyzed and classified using a neural network to assess the level of compliance of the gillnet fleet. Four key regulatory criteria assessed: (i) satellite tracking rules; (ii) net length; (iii) fishing exclusion zones; and (iv) temporal fishing closure. The findings on gillnet along the southern and southeastern Brazilian coast demonstrates a persistent pattern of non-compliance with critical regulatory measures, including net length restrictions, spatial closures, and uninterrupted transmission of vessel monitoring system (VMS) signals, even after a decade of regulatory enforcement. This combination of factors means that the greatest incidence of fishing effort, the main threat to several threatened species, especially the franciscana that occurs in areas of greater fishing effort.

Fleet Behaviour Under Economic Uncertainty: Multi‐Species Policy Scenarios for the Purse‐Seine Fishery

Tue, 31 Mar 2026 05:29:09 -0700

ABSTRACT

Managing fishing effort remains a central challenge in achieving sustainability in many fisheries, particularly where high-value species attract intense competition. In the Indian Ocean tropical tuna fishery, understanding how fishers respond to changing bio-economic conditions is essential for developing effective management. This study evaluates the influence of effort-based management measures on the size and investment behaviour of the purse-seine fleet targeting skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares). Using Random Utility Models (RUMs), we identify the key economic drivers of strategic decision-making, validate them through model evaluation, and integrate them with age-structured operating models (OMs). The RUM achieves 93% predictive accuracy, offering a robust basis for exploring policy options that balance conservation and economic objectives. Scenario testing under different cost and price conditions illustrates how economic pressures shape entry and exit decisions within the fleet.

Genetic Diversity and Impacts of Stocking on Cyprinus carpio Populations in Türkiye: Insights From Mitochondrial, Nuclear, and Microsatellite Markers

Meryem Cansu Yesiltaş, Rafet Çağrı Öztürk, Emre Keskin, Ilhan Altinok — Sun, 29 Mar 2026 23:01:04 -0700

ABSTRACT

Understanding genetic diversity and population structure is essential for the sustainable management of widely stocked freshwater species such as common carp (Cyprinus carpio). In this study, we conducted a comprehensive genetic assessment of C. carpio populations across Türkiye using mitochondrial (COI), nuclear (RAG1), and microsatellite markers. A total of 464 individuals from 29 sampling locations, including one hatchery population, were analyzed. Mitochondrial (COI) and nuclear (RAG1) markers showed low to moderate haplotype diversity, with star-like haplotype networks dominated by a few common haplotypes, consistent with demographic expansion and widespread gene flow. Microsatellite data revealed reduced genetic diversity, with mean observed heterozygosity of 0.37 and a broad range of inbreeding coefficients (F _IS = −0.765 to 1). Analysis of molecular variance indicated that most genetic variation occurred within populations (64.12%), with comparatively weaker differentiation among populations (F _ST = 0.17). Bayesian clustering and multivariate analyses showed no clear population sub-structuring, and Mantel tests detected no significant correlation between geographic and genetic distances. Overall, the genetic patterns observed are consistent with long-term stocking practices, repeated use of limited broodstock, and anthropogenic translocations, which may contribute to genetic homogenization across populations. Although common carp is not currently considered threatened in Türkiye, maintaining genetic diversity remains important for sustainable aquaculture, fishery productivity, and long-term population resilience. These findings highlight the need for continued genetic monitoring and more informed broodstock management to support the long-term genetic integrity of wild and cultured C. carpio populations.

Evidence of Density‐Dependent Growth in Juvenile Black Drum (Pogonias cromis) in the Western Gulf of Mexico

Wed, 25 Mar 2026 22:44:25 -0700

ABSTRACT

Black drum (Pogonias cromis) is an economically important marine finfish species in the Gulf of Mexico, but knowledge on the environmental factors that affect growth is limited. This study aimed to determine how juvenile black drum growth in Texas bays varies regionally and the factors that cause such variability by using samples from the Texas Parks and Wildlife Department's fishery-independent monitoring program. Generalized additive and pathway models were used to evaluate density dependence and water quality effects on the annual mean growth throughout a 38-year period. Water quality had little direct effect on annual growth, while abundance was the greatest predictive factor determining growth directly, suggesting density-dependent growth. This evidence of variable density-dependent growth among bays highlights the need to consider both fish populations and environmental variation on a bay-specific scale for effective management rather than focusing solely on a holistic approach.

RESUMEN

La corvina negra (Pogonias cromis) es una especie de pez marino económicamente importante en el Golfo de México; sin embargo, el conocimiento sobre los factores ambientales que afectan su crecimiento es limitado. Este estudio tuvo como objetivo determinar cómo el crecimiento de la corvina negra juvenil en las bahías de Texas varía regionalmente y cuáles son los factores que causan dicha variabilidad, utilizando muestras del programa de monitoreo pesquero independiente del Texas Parks and Wildlife Department. Se emplearon modelos aditivos generalizados y modelos de análisis de rutas para evaluar los efectos de la dependencia de la densidad y la calidad del agua sobre el crecimiento medio anual durante un período de 38 años. La calidad del agua tuvo poco efecto directo sobre el crecimiento anual, mientras que la abundancia fue el principal factor predictivo que determinó el crecimiento de manera directa, lo que sugiere la presencia de crecimiento dependiente de la densidad. Esta evidencia de variabilidad en el crecimiento dependiente de la densidad entre bahías resalta la necesidad de considerar tanto la dinámica poblacional como la variación ambiental a escala específica de cada bahía para una gestión efectiva, en lugar de centrarse únicamente en un enfoque general.

Logbook Data Indicate a Slight Increasing Yellow Eel Abundance in the Southern Baltic Sea

Thu, 19 Mar 2026 21:33:44 -0700

ABSTRACT

Since 2004, a logbook study has been conducted with commercial fishers to generate yellow eel specific catch per unit effort (CPUE) data in the German part of the southern Baltic Sea. By the end of 2023, this data series covers a 20-year period. Using a change point analysis, various shifts in the fyke net CPUE data series for under-sized and legal-sized yellow eels were detected, with increased mean monthly CPUEs within the last years. In contrast to the most recent recruitment trend, the CPUE data series indicate a slight increase of the yellow eel abundance in the study region. Possible causes contributing to this trend are discussed. Implications for the current debate on European eel conservation efforts are also highlighted.

Genetic and Ecological Management of Pacific Salmon Fisheries for the 21st Century

Randall E. Brummett, Ian G. Cowx, Devin M. Bartley — Thu, 19 Mar 2026 00:00:00 -0700

ABSTRACT

Based on ecological adaptation theory, tremendous effort is being spent on measures that are eliminating salmon hatcheries and fishing opportunities with the intention of protecting wild runs deemed to be of particular genetic importance to the survival of the species. New research in evolutionary biology and evidence from long-term field studies do not support these policies. Natural ecosystem variability and the complex life histories of salmon argue instead for a model based on epigenetic and phenotypic plasticity coherent with neutrality theory. Under a plasticity model, hatcheries managed within the carrying capacity of recipient streams and according to best genetic and rearing practices are not predicted to represent a threat to wild salmon, consistent with observations from the field. In addition, the scale of over-fishing and habitat destruction in the 19th and 20th centuries, compounded by projected climate change, strongly suggest that closing hatcheries justified by ecological adaptation theory is likely to further undermine genetic integrity, ecosystem productivity, and economic value of salmon, and is unlikely to result in exploitable (recreational and commercial) populations as seen in the past. Fisheries research that considers a full range of evolutionary, ecological, and social considerations is more likely to inform policy that addresses diverse values associated with Pacific salmon.

RÉSUMÉ

Sur la base de la théorie de l'adaptation écologique, d'énormes efforts sont déployés pour des mesures visant à éliminer les écloseries de saumons et les opportunités de pêche, dans le but de protéger les montaisons jugées d'une importance génétique particulière pour la survie de l'espèce. De nouvelles recherches en biologie évolutive et les résultats de études de terrain sur le long terme n'étayent pas ces politiques. La variabilité naturelle des écosystèmes et les cycles de vie complexes du saumon plaident plutôt pour un modèle basé sur la plasticité épigénétique et phénotypique, cohérent avec la théorie de la neutralité. Selon un modèle de plasticité, les écloseries gérées suivant la capacité de charge des cours d'eau destinataires et les meilleures pratiques génétiques et d'élevage ne représentent pas une menace pour le saumon sauvage, conformément aux observations sur le terrain. De plus, l'ampleur de la surpêche et de la destruction des habitats aux XIXe et XXe siècles, aggravée par le changement climatique projeté, suggère fortement que la fermeture des écloseries justifiée par la théorie de l'adaptation écologique est. susceptible de saper davantage l'intégrité génétique, la productivité des écosystèmes et la valeur économique du saumon, et qu'il est. peu probable que cela aboutisse à des populations (récréatives et commerciales) exploitables comme auparavant. La recherche halieutique qui prend en compte un large éventail de considérations évolutives, écologiques et sociales est. plus susceptible d'éclairer des politiques qui traitent des diverses valeurs associées au saumon du Pacifique.

Impact of Environmental Conditions on the Spawning Migration of Sea Trout (Salmo trutta L.) in Two Large, Sub‐Arctic River Systems

Tue, 17 Mar 2026 21:57:33 -0700

ABSTRACT

The global decline in salmonid stocks has increased the need for knowledge of local adaptations and life history strategies of salmonids. In this study, we used radio-telemetry tracking data from sea trout populations in two large high-latitude rivers to model upstream spawning migration speed of trout in response to prevailing environmental conditions and different stages of the migration. The results indicate that studied populations had similar responses to environmental changes, as trout inhabiting both rivers displayed similar responses to variation in discharge, temperature, and migrated distance covered. Higher discharge and temperature had a positive influence on trout migration speed, as did moderate discharge fluctuations. Migration distance influenced movements, as speed increased as trout moved upstream, while speed decreased late in the migration prior to spawning. These results highlight the adaptability of sea trout populations, underlining the importance of stock-specific information on habitat use and migration strategies for targeted management.

Progressive Deepening in the Depth of Fishing for a Pelagic Fish in the Arabian/Persian Gulf

Ali Alajmi, Arezoo Vahabnezhad, Abdulrahman Ben‐Hasan, Mudhi Alfadhli — Sun, 15 Mar 2026 21:08:37 -0700

ABSTRACT

Several observations indicate that fish are progressively shifting to deeper waters, with some of the recently proposed key drivers including ocean warming and fishing intensity. While the effect of ocean warming on fish migration has been extensively documented, case studies that examine the relationship between both drivers and the deepening of fish remain relatively limited. Here, we investigate a progressive change in the depth of fishing for the kingfish (Scomberomorus commerson), a widely exploited pelagic fish in the Arabian/Persian region, using fishers' perceptions and time-series datasets of fishing depth, sea surface temperature, and fishing mortality. Our findings show that most surveyed fishers indicated that the overall current mean of fishing depth is 19.44 m, whereas it was 12.43 m when fishers started fishing. Fishers' perceptions were consistent with the fishing depth time-series, which showed two key observations. First, the depth of fishing increased from 22.81 m (±13.53 m standard deviation) to 29.86 m between 2007 and 2018 (last year of data). Second, fishing deeper, from the shallowest fishing depth (22.81 m) in 2007 to the 2018 fishing depth (29.86 m; ±17.94 m standard deviation), was associated with a sharp increase in fish catch. Regression analysis showed a positive but weak association between sea surface temperature and the depth of fishing for kingfish (R ² = 0.2; p = 0.179); while consistent, the association between fishing mortality and fishing depth trends was much stronger (R ² = 0.5; p = 0.01) than with sea surface temperature. We discuss the implications for fisheries and management, highlighting the alleviation of the controllable driver, fishing mortality, through effective fishery regulations.

Exploring the Consumption of Recreational Fishing Content on Social Media

Albert Medina, Robert Arlinghaus, Valerio Sbragaglia — Sun, 08 Mar 2026 00:00:00 -0800

ABSTRACT

Social media platforms are ubiquitous and may influence how recreational fishers engage with fishing and consume fishing-related content. However, fishers' consumption patterns remain poorly characterized. Using a sample of recreational fishers from Catalonia (Spain), we examined how age, gender, and avidity predict preferences for different digital platforms and consumption frequency. Over half (55%) of surveyed fishers consumed fishing content online. YouTube emerged as the most widely used platform. Among younger fishers, Instagram showed similar prevalence to YouTube. Older fishers showed comparable engagement with Facebook and YouTube but used Instagram less. While significantly fewer women than men consumed fishing content, preferences for the most popular platforms were similar across genders. Avid fishers favored YouTube, Instagram, and Facebook, whereas less avid fishers mainly used YouTube. Our findings offer initial insights into how recreational fishers consume social media, which may inform future research and communication strategies for recreational fisheries.

Altered Fish Communities' Dynamics in 26 Healthy Lakes in Latvia—Possible Impacts of Limited Fisheries Management

Wed, 25 Feb 2026 20:35:41 -0800

ABSTRACT

This study investigated fish community dynamics in 26 healthy Latvian lakes to determine the balance between top-down versus bottom-up controls. We employed a multi-methodological approach, combining multi-mesh gillnetting with structured stakeholder interviews and management plan analysis to quantify anthropogenic pressures. We hypothesized that fish community regulation would diverge based on the presence or absence of top predators. Results demonstrated a strong negative correlation between large piscivores and omnivorous fish biomass, validating trophic cascade predictions. While lake area and depth influenced fish length, bottom-up drivers like total phosphorus had limited explanatory capacity. Interestingly, structured stakeholder interviews revealed that fisheries resource management might be an important predictor of ecosystem health. Lakes with perceived low illegal fishing pressures maintained healthy predator proportions, while those under higher pressure had notably fewer large piscivorous fish. We conclude that in otherwise healthy lakes, effective fisheries regulations' enforcement might be more critical than nutrient management for maintaining balanced fish communities.

Using Catch Data to Estimate Changes in Global Commercial Abalone Abundance

Douglas Crookes — Tue, 24 Feb 2026 03:12:51 -0800

ABSTRACT

Changes in global wild capture production of abalone are explored to infer potential changes in biological stocks. The study found that 77% (or 10 out of the 13) of the countries that reportedly caught abalone in the wild have experienced declines in catches between 1980 and 2023, and on aggregate catch declined by almost 83% between 1980 and 2023. In order to test whether dynamic closures would be a solution, a model of regulated open access is developed for abalone at Table Mountain National Park (TMNP). The model shows that dynamic closures are only applicable for fisheries with well-developed stock assessment capabilities and where illegal fishing is largely absent. The TMNP probably does not fall into this category, although the catch restriction component of the model probably still applies. Solutions for fisheries where these conditions are not met are then discussed with reference to the socio-political literature.

Long‐Term Climatic Variations Influencing Fish Stock Population Dynamics and Future Projections for Sustainable Fisheries Management

Kakoli Banerjee, Pramod Kumar Bindhani, G. Jayanti Reddy, Rakesh Paul — Sun, 15 Feb 2026 22:49:12 -0800

ABSTRACT

This study aims to evaluate the influence of long-term variations in sea surface temperature (SST), salinity, and pH on marine fish catch and species composition in coastal India. Secondary data (during 1985–2022) on oceanographic parameters were sourced from NOAA, while fish catch data of Bay of Bengal (BoB) and Arabian Sea (AS) were obtained from Central Marine Fisheries Research Institute (CMFRI). The Shannon–Wiener diversity index analysis and different forecasting models (ARIMA, Linear, and Polynomial) were employed for temporal forecasting till 2051. Diversity index results indicated that Elasmobranchs (3.24) were the predominant commercially important (CIF) taxa in both BoB and AS, whereas Threadfins and Flatfishes (3.20) dominated the trash fish (TF) assemblage in BoB, and Bombay duck (3.24) was the most abundant TF species in AS. Forecast projections revealed an initial decline in CIF and TF stocks in BoB, followed by a gradual recovery until 2051, while AS exhibited a consistent increase. These findings underscore the necessity for adaptive marine resource management and blue economy strategies to ensure sustainable fisheries under changing climatic conditions.

Disentangling the Drivers of a Piscivorous Intra‐Annual Cohort and the Contributions of Three Cohorts to Early‐Year Class Strength in Pikeperch (Sander lucioperca)

Wed, 11 Feb 2026 22:06:14 -0800

ABSTRACT

Using pikeperch (Sander lucioperca) as a model species, we investigated the factors influencing fluctuations in the abundance of piscivorous intra-annual cohorts and assessed the role of three distinct cohorts: extremely small (ES), ordinary (or mid-sized) fingerlings, and piscivorous in shaping year-class strength. Our analysis was based on 13 years of data (2003–2024) collected in the Lipno Reservoir, Czechia. Using LASSO for variable selection among 45 potential covariates and subsequent Generalized Additive Model (GAM) construction, our results revealed that a higher abundance of ES conspecifics and young-of-the-year (YOY) perch, coupled with increased densities of large cladocerans in July, positively impacted the abundance of the piscivorous intra-annual cohort. The abundance of 1+ pikeperch was positively influenced by the abundance of piscivorous and ordinary cohorts recorded in the preceding year. We concluded that all three intra-annual cohorts contribute to the year-class strength of pikeperch, with piscivorous and ordinary cohorts having a more direct effect, while ES intra-annual cohorts indirectly support the piscivorous cohort by serving as prey.

Using Eye Lens Stable Isotopes to Identify the Rearing Origin of Fall Age‐0 Walleye (Sander vitreus)

Wed, 11 Feb 2026 02:38:15 -0800

ABSTRACT

Isotope values in fish eye lenses may be useful in differentiating rearing origins. We compared eye lens isotopic values of fall fingerling age-0 walleye (Sander vitreus) reared in a hatchery pond, a recirculating aquaculture system (RAS), and a natural lake. Using 10 fish per rearing source, we delaminated layers from one eye lens per fish to assess temporal changes in carbon (δ¹³C) and nitrogen (δ¹⁵N) and pulverized the whole second eye lens for δ¹³C, δ¹⁵N, and sulfur (δ³⁴S). RAS-reared walleye values exhibited high precision among individuals and were δ³⁴S enriched. Pond-reared walleye had lower δ¹³C and δ¹⁵N core values compared to other rearing sources. For δ¹³C and δ¹⁵N, values remained consistent among layers for RAS-reared walleye, δ¹⁵N slightly increased for pond-reared and lake-reared walleye, and δ¹³C increased substantially among subsequent layers in pond-reared walleye. Bayesian 95% ellipses did not overlap among rearing sources. These results demonstrate that eye lens stable isotope analysis may be a useful tool for differentiating hatchery-reared and wild large fingerling walleye, specifically from RAS- and pond-reared sources.

Stock Status and Growth Parameters of Pronghorn Spiny Lobster (Panulirus penicillatus) in the Prigi Waters, South Java Sea, Indonesia

Dhita Widhiastika, Am Azbas Taurusman, Ronny Irawan Wahju — Tue, 10 Feb 2026 00:00:00 -0800

ABSTRACT

Lobster (Panulirus spp.) is an important fisheries commodity in Indonesia for local and international markets. According to Minister of Marine Affairs and Fisheries (MMAF) Decree Number 19/MMAF/2022, the utilization level of lobsters in the Indonesian Fisheries Management Area (FMA 573), including Prigi Waters, has been “over-exploited” status with the utilization rate (E = 2.0). Similarly, the Marine and Fisheries Agency of Trenggalek Regency, East Java Province reported that the lobster annual catch has decreased by 3.28 tons from 2021 to 2022. Meanwhile, data and information regarding lobster fisheries are limited in this area. This study aims to evaluate the utilization status of the pronghorn spiny lobster (Panulirus penicillatus) in Prigi Waters based on parameters of growth and Length-Based Spawning Potential Ratio (LB-SPR). Data on catch and effort for the lobster fishery from January 2021 to December 2023 were sourced from local collectors. Meanwhile, the biological parameters of P. penicillatus were directly measured from fishers' catches between October 2023 and January 2024, resulting in a total of 2115 individual samples. This study revealed that P. penicillatus catches in Prigi Waters were dominated by legal-sized individuals (> 60 mmCL). The growth pattern is negative allometric. The growth parameters of this species were L _∞ = 133.74 mm and k = 0.50/year. The exploitation rate (E) was 0.57/year, and the spawning potential ratio was about 30%, indicating a “fully exploited” status. Therefore, this study recommends maintaining the level of fishing effort targeted at P. penicillatus, and replacing the illegal fishing method of compressor diving with traps.

Linear Growth Patterns and Growth Parameter Dynamics in Northern Pike (Esox lucius) Populations From Non‐Flowing Water Bodies Across Their Natural Range

Feodor Lobyrev, Pavel Emeliyanenko — Fri, 06 Feb 2026 03:13:46 -0800

ABSTRACT

Analysis of 60 northern pike (Esox lucius) populations, assembled from published studies spanning the species' range and restricted to non-flowing (lentic) systems, and analyzed using the von Bertalanffy growth function (VBGF), revealed substantial heterogeneity in growth parameters. Growth coefficients (k) ranged from 0.01 to 0.72 year⁻¹, asymptotic lengths (L∞$$ {L}_{\infty } $$) from 53 to 976 cm, and maximum observed lengths (Lmax$$ {L}_{\mathrm{max}} $$) from 35.1 to 113.2 cm. Biologically defensible thresholds were identified at k ≥ 0.25 year⁻¹ and L∞$$ {L}_{\infty } $$ ≤ 113.2 cm, lose biological interpretability under realistic demographic constraints. Within this framework, the VBGF served two complementary roles: as a predictive model of linear growth trajectories and as a diagnostic representation of growth-trajectory shape. The Lmax/L∞$$ {L}_{\mathrm{max}}/{L}_{\infty } $$ ratio emerged as an informative descriptor, capturing ontogenetic growth patterns along a continuum from near-linear (Lmax/L∞$$ {L}_{\mathrm{max}}/{L}_{\infty } $$ ≈0.07) to fully asymptotic (Lmax/L∞$$ {L}_{\mathrm{max}}/{L}_{\infty } $$ ≈1.00) growth. This metric links empirical size-at-age observations with the degree to which asymptotic growth is expressed within finite lifespans. Integrating VBGF parameters (k, L∞$$ {L}_{\infty } $$) with empirical descriptors (Lmax$$ {L}_{\mathrm{max}} $$, lifespan) and cumulative thermal exposure (growing degree-days) revealed two coherent growth regimes in northern pike along latitudinal thermal gradients: fast-growing populations reaching moderate asymptotic sizes rapidly, and slow-growing populations characterized by low growth coefficients and very large theoretical L∞$$ {L}_{\infty } $$ despite similar observed maximum lengths. Taken together, the Lmax/L∞$$ {L}_{\mathrm{max}}/{L}_{\infty } $$ ratio, combined with biologically grounded thresholds for k and L∞$$ {L}_{\infty } $$, provides a parsimonious screening tool for identifying non-asymptotic growth trajectories and a temperature- and time-explicit framework for evaluating the expression of asymptotic growth across climatic gradients.

Guidelines to Make Swimming Crab (Portunus trituberculatus) Pot Fishery Size Selective

Wed, 04 Feb 2026 02:35:47 -0800

ABSTRACT

Pot fisheries are a crucial component of small-scale fisheries worldwide, characterized by their low environmental impact, high species selectivity, and superior catch quality. However, these fisheries are often constrained by poor size selectivity, which results in substantial bycatch of juvenile target species and remains a major challenge for pot fisheries management globally. Incorporating escape gaps or increasing mesh size are effective technical measures to improve pot size selectivity and reduce the unintended capture of undersized individuals. However, the implementation of these measures typically depends on traditional experimental sea trials, which are costly, time-consuming, and restrict the number of gear designs that can be tested. This study focuses on the Chinese swimming crab (Portunus trituberculatus) pot fishery, which is the most economically important crab fishery along the Chinese coast. Laboratory experiments were conducted to establish predictive models for the size selectivity potential of swimming crab in pots. The size selectivity potential of a wide range of escape gap shapes and sizes, as well as mesh size and mesh opening angle, were investigated. The predictive models for the size selectivity potential were compared to earlier sea trial results and demonstrated their usefulness to predict swimming crab size selectivity. Based on these models, we provide guidelines to make swimming crab pot fishery size selective, which would contribute to the sustainable management of this pot fishery.

Post‐Release Mortality of European Bass (Dicentrarchus labrax) Discarded From Small‐Scale Estuarine Fishing

Fri, 23 Jan 2026 22:10:56 -0800

ABSTRACT

Estuaries provide essential habitats for many fish species, but their confined and accessible nature may increase fish vulnerability to capture, and few empirical studies have quantified the value of restricting net fisheries in such areas. Furthermore, management measures for some fisheries promote discarding (e.g., of European sea bass; Dicentrarchus labrax), yet the mortality of fish discarded from small-scale inshore fisheries is poorly understood. We used condition assessments, Reflex Action Mortality Predictor scores and acoustic tracking to evaluate post-release mortality of bass captured in small-scale estuarine netting and angling. Gillnet-caught bass exhibited a range of stress responses and 20%–24% mortality shortly after capture, whereas angler-caught bass showed no short-term post-release mortality. Six-month survival of fish released in good condition was > 80% for both gear types. However, strong site fidelity and residency were observed which could increase recapture risk. Our findings underscore the potential benefits of prohibitions of netting in sensitive estuaries and can inform fisheries discards management.

Management Implications of Mesopelagic Forage Fisheries for Bigeye Tuna Stocks

Ciara Willis, Di Jin, Melina Kourantidou, Simon R. Thorrold — Fri, 23 Jan 2026 00:00:00 -0800

ABSTRACT

Many large marine predators forage on mesopelagic fish stocks, including commercially valuable tunas. The mesopelagic is under increasing interest for commercial exploitation, given its large biomass with potential to supply fishmeal for aquaculture feed or fish oil. However, the implications of large-scale mesopelagic fisheries on tunas and other predators may be substantial. Here, we adapt a bioeconomic model with a new predator–prey dynamic to evaluate the effects of potential commercial-scale mesopelagic fisheries on bigeye tuna (Thunnus obesus). Specifically, we use a novel diet share model term and the latest stable isotope food web data to operationalize predator–prey interactions. Model results highlight the importance of accounting for the predator–prey interactions in management of mesopelagic fisheries and demonstrate the sensitivity of equilibrium economic and ecological conditions for the tuna stock under different price and cost scenarios. Overall, this work suggests that a new mesopelagic fishery could be economically viable in and of itself, but may have significant negative impacts on existing tuna fisheries by reducing forage availability.

Impacts of Marine Recreational Fishing on Social and Economic Benefits in a Marine Multiple Use Area, the Marine Estate, New South Wales, Australia

Wed, 21 Jan 2026 21:15:41 -0800

ABSTRACT

Economic and social aspects of recreational fishing that have been increasingly studied indicate different motivations and enjoyment among participants. However, economic and social interactions between marine recreational fishers and other users of the marine environment have been less studied. We examined impacts of marine recreational fishing activity on economic and social benefits from a marine multiple use area in the New South Wales Marine Estate. Risk assessments are commonly used to assess risks to ecosystems resulting from commercial activity, but are less commonly used to assess risks of recreational fishing on benefits to all users from marine spaces and ecosystems. A risk assessment framework was used to identify key threats from recreational fishing to economic and social benefits derived from the Marine Estate. Assessment evidence was from the literature, Government management agencies, media and stakeholder reports, and expert opinion. This risk assessment approach to assess social and economic impacts can contribute to management of other marine-based activities internationally, including recreational fishing and other activities in multiple-marine use areas.

Post‐Release Survival of the Pelagic Stingray (Pteroplatytrygon violacea, Bonaparte, 1832) in French Longline Fisheries in the Northwestern Mediterranean Sea

Sat, 17 Jan 2026 03:50:11 -0800

ABSTRACT

Bycatch remains a critical challenge in global fisheries, even when using selective gears such as longlines. In the French longline fishery targeting Atlantic bluefin tuna (Thunnus thynnus) in the Gulf of Lion, the common pelagic stingray (Pteroplatytrygon violacea) is the primary bycatch species. This study investigated the post-release survival and behaviour of 38 stingrays (38–75 cm disc width) captured during the spring–summer seasons of 2022 and 2023, using electronic tagging (MRPats, sPats, and PSATLife). A clear seasonal trend was observed, with smaller individuals more frequently caught in summer, likely linked to warmer water conditions that also reduced tag retention time (1–70 days). Survival was estimated using the Kaplan–Meier method, accounting for uncertainty in post-release status determination. The results indicated high survival rates ranging from 73% to 100% (median 87%), demonstrating the species' strong resilience to capture and handling. Tagging data also revealed extensive vertical and horizontal movements, with individuals reaching depths of nearly 700 m and traveling over 20 km per day. This brings new and valuable information on this poorly known species, albeit common in the Mediterranean, for the sustainable management of exploited resources in this area.

Effects of the Invasive Round Goby on Swedish Recreational Fishing Values

Göran Bostedt, Ola Carlén, Rahmat Naddafi, Ann‐Britt Florin — Wed, 14 Jan 2026 00:00:00 -0800

ABSTRACT

The round goby, an invasive fish from the Black and Caspian Seas, has spread to Swedish waters, threatening recreational fisheries. We modeled impacts on the future recreational fishery in Sweden using data from a recreational fishing survey, and estimated effects of the round goby on other fish species. Values attached to recreational fishing were estimated using a travel cost approach. Catch and consumer surplus were compared before and after a 10-year increase in round goby abundance. Overall impacts of a 10-year increase in round goby abundance in Swedish waters would reduce the present value of consumer surplus by SEK 379-million (EUR 33-million). Any management action keeping a status quo in round goby impact with a price less than about 3 million EUR yearly would hence be justified. This study highlights how aquatic invasive species can cause substantial social losses and that proactive management may be cost-efficient.

High Cost and Low Trust: Insights From Qualitative Commercial Fishing Cost Data in the Northeast United States

Tue, 13 Jan 2026 00:00:00 -0800

ABSTRACT

In fisheries management, socioeconomic data, specifically qualitative data analysis, is often underutilized. This study qualitatively analyzed a primary federal data collection effort in the Northeast United States, The Greater Atlantic Region Commercial Fishing Business Cost Survey. This analysis focused on how commercial harvester perceptions of business costs and the industry evolved during 2006–2022. The results show that harvesters initially described perceptions of not generating enough profit to sustain a livelihood, as well as feelings of industry uncertainty, mismanagement, and dissatisfaction. These perceptions became drivers of increased harvester distrust of managers and management processes. This research demonstrates the need for incorporating harvester perceptions in future policy analyses to understand and reduce financial and systemic burdens. Use of harvester perceptions illuminates areas of concern that need to be addressed to strengthen relationships while simultaneously encouraging knowledge co-production, co-management, and increasing sustainability of fishery resources. Here, we exemplify the importance of utilizing qualitative data to provide valuable insights such as a deeper understanding of social dynamics and stakeholder perspectives and go on to explore the root causes and evolution of distrust between harvesters and managers. This study offers applications to better assess, address, mitigate, and rebuild trust to meet complex resource management goals.

Recompression Improves Release Success in Pollack (Pollachius pollachius): A Step Towards Assessing Post Release Mortality in a Recreational Fishery

Fri, 09 Jan 2026 20:44:34 -0800

ABSTRACT

The recreational fishery for pollack (Pollachius pollachius) in the northeast Atlantic is impacted by the species' high sensitivity to barotrauma. When captured at depth and brought to the surface, gas expansion within the peritoneal cavity can cause a variety of injuries and hinder release. Via an experimental weighted cage, this study evaluated the efficacy of releasing Pollack at depth as a barotrauma mitigation strategy. We found that depth-release significantly increased the probability of released Pollack displaying an active escape response to 83%, compared to 56% for surface-released fish; however, increased capture depth and fish size negatively affected success. Camera observations of depth-released Pollack confirmed the recovery of vital reflexes (vestibulo-ocular reflex, equilibrium maintenance) within 1.5–4 min. Further acoustic telemetry demonstrated that individuals subsequently displayed active dispersion from the release site (0.1–23.8 km) and showed active vertical movements for up to 6 months post-release. These findings indicate that depth-release improves survival outcomes, though further research is required to optimise release methods in open-water environments.

Advancing the Crucial Notion of “Interoperability” in Catch Documentation Schemes

Gilles E. Hosch, Shelley C. Clarke — Mon, 14 Apr 2025 20:44:06 -0700

ABSTRACT

Catch documentation schemes (CDS) use validated documents such as catch certificates to establish and track the legal provenance of fish, thereby aiming to reduce the flow of illegal fishing products into markets. When a CDS is implemented independently to protect a single market, an inherent risk is that illegal, unreported, and unregulated (IUU) fishing products will be diverted to other supply chains, including those with weaker CDS. The recent proliferation of such CDS has resulted in more types of catch certificates in circulation. This can lead to inadvertently increasing opportunities for laundering uncertified fish when these CDS lack internal and external mechanisms to prevent attaching catch certificates to fish that do not actually have legal provenance. To support essential and effective cooperation, CDS that currently operate independently should actively promote interoperability to facilitate data exchange and prevent fraud. Recently announced improvements to the European Union's (EU) CDS address these issues and boost the prospects for interoperability between the world's largest CDS and other CDS with compatible designs. This invites collaboration with new and still evolving CDS, such as the one recently implemented by Japan based on the EU model, to their individual and collective advantage. Interoperability is possible at levels ranging from manual, case-specific investigation of suspicious shipments to automated cross-checks between systems or even a fully integrated “super CDS”. Increasing cooperation amongst schemes, grounded in design-based and functional interoperability, is expected to lead to stronger ring-fencing of and measurable reductions of IUU fishing products in CDS-protected markets.