ABSTRACT The integration of separate sexes in stock assessment models represents an advancement towards more realistic modeling of interactions between fisheries and target species. However, increased model complexity can also introduce additional uncertainty into the modeling process. Assuming the same biological parameters for males and females in a single‐sex model may not be appropriate for species with significant sexual size dimorphism (SSD), such as the European hake ( Merluccius merluccius ). In this study, we investigated how single‐sex assessment models assuming biological traits (I) combined for males and females, and (II) the female‐only, compare to the population dynamics of a reference two‐sex model, which accounts for sex‐specific differences in growth and natural mortality ( M ). Results show that single‐sex approaches, particularly the female‐only model, may lead to a different population status, underscoring the sensitivity of assessment outputs and management quantities to sex‐structure assumptions in SSD species. However, when sex‐structured survey data are unavailable, a single‐sex combined model may still provide a reasonable approximation of a two‐sex dynamic. Additionally, the two‐sex model's specific indicators such as sex ratio‐at‐length and operational sex ratio (OSR) provide further insights into stock and fishery dynamics, facilitating more informed decision‐making and enabling the development of fleet‐tailored management strategies. Our findings underscore the need for two‐sex models in species with marked SSD and advocate for investment in sex‐specific data collection and refined diagnostic tools to accurately assess model adequacy.
ABSTRACT Shark populations are declining globally and the effectiveness of marine protected areas (MPAs) as a conservation tool may vary by species and environmental context. This study assessed space use and residency of smoothhound sharks ( Mustelus mustelus )—an endangered, yet highly exploited shark—in relation to spatial protection and fishing risk across three areas off the southern coast of South Africa. Passive acoustic telemetry data (2016–2023) from 37 individual sharks were analysed using residency indices and generalised additive models. Smoothhounds exhibited high site fidelity, with small daily home ranges (< 10 km 2 ). Residency showed a weak but significant negative relationship with fishing risk, indicating reduced residency in areas of higher fishing pressure. Residency was consistently higher within a MPA and adjacent bay waters, as compared to a nearby unprotected bay. These findings suggest that smoothhounds may respond to spatial protection and suggest that extending protection to the MPA‐adjacent high‐use areas could enhance conservation outcomes.
ABSTRACT Microplastic (MP) pollution—plastic particles smaller than 5 mm—is now ubiquitous across marine, estuarine, and freshwater environments and poses a pervasive threat to global fisheries. This review synthesises current evidence on MP occurrence, trophic transfer, and sub‐lethal physiological effects in fisheries‐relevant species and their consequences for fisheries productivity and food safety, with particular attention to Indonesia and other tropical, developing‐country contexts underrepresented in the global literature. Microplastics have been detected in over 926 seafood species, with Asian waters among the most contaminated regions, and are documented to cause oxidative stress, growth impairment, reproductive dysfunction, immunosuppression, and neurotoxicity in fish, with trophic magnification factors exceeding 4 reported in oceanic food webs. These effects carry direct implications for fisheries management, including declining population health, reduced recruitment, and threats to food safety, yet regulatory frameworks remain inadequate, with no binding MP limits established by major food safety bodies. We outline management‐oriented recommendations—monitoring protocols, gear modification, and integration of MP risk into stock assessment—and priority directions for future research.
Diadromous fish such as Petromyzon marinus and Alosa alosa support economically and culturally important small-scale fisheries in Portugal but face increasing pressures such as habitat degradation, climate change, and overexploitation. In response, a voluntary label-of-origin system was introduced in selected river basins to enhance product differentiation and improve traceability. This study evaluates the implementation and performance of this initiative in the Mondego and Vouga river basins. A mixed-methods approach combined analysis of labeling records with stakeholder interviews and questionnaires, complemented by a multi-criteria assessment of implementation challenges. Results indicate generally positive stakeholder perceptions regarding trust and market valorization; however, adoption remained inconsistent and highly dependent on institutional facilitation. Key constraints included limited traceability information, operational difficulties in tag application, and fragmented governance responsibilities. The findings suggest that while voluntary labeling initiatives may enhance product transparency and perceived value, their effectiveness depends on operational feasibility, regulatory integration, and sustained institutional support. This case study provides empirical insights into the opportunities and limitations of traceability-based instruments for governance and management in inland small-scale fisheries.
Knowing the relationship between catch per unit effort (CPUE) and population density is crucial for the management of recreational fisheries. We conducted standardized angling for pike in 16 lakes (3.4-22.1 ha) to test whether lure type, color, and pike density affect CPUE and the size of captured fish. Angling CPUE (fish h-1 km-1) was statistically significantly related to pike density (fish ha-1), despite the high variation and uncertainty in CPUE estimates. Lure type affected CPUE, whereas water temperature, use of a boat, time of day, and transect fishability had no effect. CPUE was higher when using spoons compared to spinnerbaits, but lure color (fluorescent vs. natural) had no effect. The length of captured fish was not dependent on lure type or color. Our results suggest that a predefined protocol may help reduce variation in CPUE data; however, it does not yet allow for reliable estimation of pike density.
Understanding male sexual maturity in penaeid shrimp is crucial for stock assessment and size-based management; however, maturity criteria remain heavily biased toward females and rarely validated for males. This study evaluated whether petasma fusion is a reliable external indicator of male sexual maturity in white shrimp Penaeus schmitti from Northeast Brazil and estimated size at first maturation using an integrative morphometric, histological, and statistical approach. Forty-five males were classified according to petasma condition, morphometrically measured, histologically examined along the reproductive tract, and analyzed using individual-level binomial logistic regression. The estimated cephalothorax length at first maturation was CL50 = 2.24 cm (95% CI: 2.06-2.43), with a strong model performance (Nagelkerke R-2 = 0.80). Histological analysis revealed complete categorical agreement between external morphology and internal reproductive status: all males with unfused petasma lacked mature spermatozoa and exhibited only early germ cells, whereas all males with fused petasma presented the complete spermatogenic series and fully differentiated spermatozoa in the terminal ampulla. The relationship between petasma length and body size showed negative allometry, indicating a proportionally smaller investment in petasma growth relative to somatic growth. ANCOVA detected a significant maturity effect on the intercept, but not on the slope, demonstrating a discrete proportional change in petasma dimensions at maturation, rather than a change in growth trajectory. These findings demonstrate that petasma fusion is a robust and nondestructive indicator of physiological maturity in male P. schmitti. The results of the analysis combining petasma, histology, and length at first maturity indicated that petasma is a reliable indicator for validating physiological maturity and that male reproductive indicators should be formally incorporated into penaeid fishery management structures.
ABSTRACT The waved albatross ( Phoebastria irrorata ) is a critically endangered species ranging from the Galápagos Islands to northern Chile, often foraging in coastal waters off Peru. We assessed bycatch in Peruvian small‐scale fisheries to identify high‐risk gear types and areas of waved albatross bycatch using an interview‐based approach. Semi‐structured interviews were conducted with 361 fishers across 11 ports in northern and central Peru between April 2022 and June 2023, covering longlines, gillnets, and jigging fisheries. Bycatch was reported in 10 of the 11 ports, with an estimated annual total number of interactions (includes animals released alive, injured, or potentially dead) exceeding 1200 waved albatrosses, mainly in surface longline and gillnet fisheries. Multiple Correspondence Analysis showed associations between bycatch events, large pelagic fisheries, and gear characteristics such as J‐hooks and large mesh sizes. Spatial variation in bycatch rates and overlap with key foraging areas highlight the need for region‐specific management. Overall, waved albatross bycatch remains widespread along the Peruvian coast, emphasizing the urgency of targeted mitigation, improved monitoring, fisher participation, and strengthened Peru–Ecuador cooperation.
Fish are an important commodity to communities in the Lower Mekong Basin (LMB), representing the most important protein source for millions of people in the region. Sustainable fisheries do not only require sustainable fish catches but also improve benefits and return to fishing communities through the fisheries value chain. Fish trade was surveyed in 12 provinces in the LMB to quantify the diversity, abundance and prices of fish species between landing sites and urban markets to understand mark-up values through the value chain as an entry point to designing a strategic intervention to improve financial returns to fishers. Across the LMB, mark-up in prices paid to fishers at landing sites and those reportedly charged to consumers in urban markets ranged from 36% to 110% on average, and reached as high as 611% for certain species. Cambodia and Vietnam exhibited similar average mark-up values at 104% and 112% respectively (range 0% to 611%), while Lao PDR and Thailand both showed lower mark-up prices at 36% (range 0%-175%). This highlights the potential for higher economic returns to fishing communities. Of 136 species in 11 major ecological guilds recorded from urban markets, potamodromous migratory main channel refuge seeker species (Guild 4) and potamodromous short-distance migratory main channel spawner species (Guild 3) were the most diverse guilds that contributed 47% of species and were present in markets in all countries. Guild 3 also dominated the weight sold and individual species value, reflecting their high market demand in all countries. These findings show the added value generated in small-scale inland fisheries systems in the LMB and justify further investment and research on how to improve financial returns to fishers, without necessarily increasing fish prices, which is essential to increase motivation for conservation of fish stocks and their habitats.
Fish farming is a part of the agricultural sector that provides economic, social, and ecosystem functions that are important for reducing food and nutrition insecurity for the poorest and most marginalized groups around the world and particularly crucial for poverty reduction in African countries. While many studies are preoccupied with developed countries, there is less research focusing on Sub-Saharan Africa. In Ethiopia, research on the governance of fishing management is relatively scarce. Therefore, this study aimed to analyze the implications of environmental governance for fishing management. Purposive and convenience sampling were used to select respondents. Survey data were collected from 180 fishers, with three key informants. Principal component analysis (PCA) and factor analysis (FA) were used to analyze the quantitative data. The results show a low level of environmental governance practices in the two study areas, a lack of attention to the fishing sector, political instability being the major challenge in one of the study areas, top-down governance approach, and fishing as a characteristic of poverty. We argue that strong political drive, capacity, and stability are crucial for effective environmental and governance. Interactive governance of natural resource systems, adaptive and collaborative environmental governance are needed to promote sustainable fishery management across Africa. Insights from this study can contribute to the implementation of a new framework for future sustainable fishing management. The proposed framework critically engages with the challenges and interventions that are needed to positively influence fishing management and can fill current geographical and topical research gaps.
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.
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.
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.
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.
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.
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.
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.
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.
