Fisheries Management Research Articles

Key drivers of at-vessel mortality in demersal sharks.

Chondrichthyans are highly vulnerable to fisheries overexploitation, and postcapture mortality poses a significant threat to most species. Global bycatch mitigation guidelines recommend adopting hierarchical decision-making approaches tailored to species-specific vulnerabilities and socioeconomic and regulatory contexts. Effective implementation of such strategies requires robust understanding of the factors driving vulnerability to postcapture mortality. To address this need, we developed a machine learning method to identify key drivers of at-vessel mortality (AVM) based on a broad set of biological, environmental, and fishing-related parameters. We sought to reveal interactions among predictors, nonlinear responses between these variables and mortality risk, and threshold values beyond which the likelihood of mortality increased markedly. We applied this approach to trawl bycatch data on small-spotted catshark (Scyliorhinus canicula) and blackmouth catshark (Galeus melastomus) in the western Mediterranean. Body size, air temperature, and on-deck time emerged as the primary AVM drivers. Mortality risk increased substantially at temperatures above 20°C for S. canicula and 16°C for G. melastomus, with on-deck exposure exceeding 15min, and when body size was below 40 and 55cm, respectively. Identification of these drivers and thresholds provides valuable insights for bycatch mitigation; can inform strategies for more threatened, closely related, or physiologically and ecologically similar species; and may support management authorities in adopting targeted bycatch avoidance strategies, gear selectivity, and mortality reduction measures. Such measures can be tailored to specimens, areas, and periods of heightened mortality risk to maximize effectiveness. Furthermore, our scalable modeling approach offers a robust tool for identifying critical AVM drivers across regions and species, and its applicability can be extended to broader fisheries management and global conservation efforts.

Alternating ecosystem states driven by an invasive fish in a life-history intraguild predation system

Prey species that compete with or consume early life-stages of their primary predator (i.e., life-history intraguild predation [LHIGP]) can generate alternate ecosystem states and distinct shifts in predator demographics. Identifying ecological conditions underlying alternate states can inform adaptive management of LHIGP-driven ecosystems and fisheries. We developed a time-varying, stage-structured population modeling framework to explore the dynamics of a Walleye (Sander vitreus) population supported by invasive Rainbow Smelt (Osmerus mordax), a widely introduced forage fish that can negatively affect Walleye recruitment. Our model identified two distinct and cyclic states over a 42-year time-series. The first was characterized by low smelt abundance, elevated Daphnia density and Walleye recruitment, but poor Walleye growth and survival to larger size, while inverse patterns characterized the second state. Strong state-dependent shifts in predator vital rates and population structure emphasized the need for flexible management approaches (e.g., stocking, harvest regulations) to maintain fisheries quality and population sustainability. Our modeling framework is broadly applicable to understanding the dynamic nature and informing adaptive management of non-stationary systems, such as those characterized by LHIGP.

Heterogenization of marine catch assemblages over the past two decades in China

Abstract The trajectories of marine catch assemblages in response to anthropogenic change at large temporal and spatial scales remain elusive, posing a threat to Marine fishery biodiversity and food security. Here, we use data collected from the China Fishery Statistical Yearbook that spans 2003-2019 to systemically and quantitatively assess the trajectory change of marine catch assemblages and the drivers. Over the past two decades, we observed obvious temporal heterogenization in species taxa and structure for both occurrence and abundance-based dissimilarity in marine catch composition, with key fish species identified as the primary drivers. The heterogeneity rate is particularly pronounced in low-latitude southern regions. While overall species richness remained relatively stable, these findings highlight the critical need to shift our conservation focus from biodiversity loss to composition change as a key indicator of marine ecosystem health. These findings can aid in the creation of sustainable marine conservation and fisheries management decisions to rebuild the resilience of marine fishery stocks.

Implications of predator-prey dynamics for single species management

Despite the large body of research suggesting that the population dynamics of fishes are affected by their predators, the majority of fisheries management authorities use single-species models that assume individual populations are independent of one another. However, research is needed to identify the relevance of predation to single-species management while accounting for the feedback between management and fish populations. We conducted a management strategy evaluation (MSE) using two multi-species models as operating models to assess the performance of single-species management. We evaluated the ability of single-species management to achieve single- and multi-species reference points, maximize catch, minimize catch variability, and reduce model bias and variance. The incorporation of predation mortality and full feedback control in our MSE allowed us to account for trophic dynamics and continued data collection and assessment. Our results demonstrate that single-species management strategies are robust to predation mortality across two systems with differing trophic dynamics. The relative performance varied depending on the assessment and harvest control rule used. The selection of an optimal management strategy will therefore depend on management objectives.

A spatial analysis of fishing license sales and population data: Implications for predicting angler participation

ABSTRACT Objective We sought to understand how social and geographic factors influence fishing license sales at spatial scales. We tested the predictive capacity of human population density, educational attainment, median age, median income, gender, and distance to public water bodies on license sales at the ZIP code level across the U.S. state of Illinois in 2021. Methods We compared an ordinary least squares multiple regression model with a logistic regression model to evaluate the effect of each variable on the rate of fishing licenses sold on average across the state. We then used a multiscale geographically weighted regression model using ZIP code of angler residence as a spatial tool to understand how effects varied by region. Results The model results indicated that whereas human population density negatively predicted average license sale rates across the state, age, income, population density, educational attainment, and distance to fishable water bodies predicted license sales only when their correlations were allowed to vary geographically. Conclusions Evaluating spatially aggregated data at the population level may provide insight into why license sales vary regionally across the United States. The use of spatial modeling to understand fishing participation is recommended to provide insight on how fishery managers can prioritize efforts to increase license sales regionally and better understand the cause of declines where they occur.

Low contamination and rapid depuration of domoic acid in the variegated scallop, Mimachlamys varia.

Low contamination and rapid depuration of domoic acid in the variegated scallop, Mimachlamys varia.

Untangling the net: Redefining fisheries management with fully documented fisheries

Untangling the net: Redefining fisheries management with fully documented fisheries

The quiet voices of French territories in tuna fisheries management

The quiet voices of French territories in tuna fisheries management

Microplastic occurrence in 21 coastal marine fish species from fishing communities on Viti Levu, Fiji.

Microplastic occurrence in 21 coastal marine fish species from fishing communities on Viti Levu, Fiji.

Comparison of length-weight relationships of three economically important shrimp species in Iskenderun Bay, Northeastern Mediterranean

This study investigates the length-weight relationships (LWR) of three economically important shrimp species (Farfantepenaeus aztecus, Penaeus semisulcatus, and Metapenaeus monoceros) in İskenderun Bay, Northeastern Mediterranean, using data collected between October 2023 and November 2024. A total of 579 specimens were analyzed, with F. aztecus contributing the highest sample size (238 individuals), followed by P. semisulcatus (214) and M. monoceros (127). Carapace length (CL) and weight (W) measurements revealed interspecies differences. The average carapace length was 5.66 mm for F. aztecus, 6.63 mm for P. semisulcatus, and 5.08 mm for M. monoceros. Average weights were 32.81 g, 39.68 g, and 31.48 g, respectively. Growth patterns, determined by the parameter 𝑏, showed distinct gender differences. Females generally exhibited negative allometric growth, while males displayed either isometric or positive allometric growth, depending on the species. Statistically significant differences in growth types were observed, particularly in M. monoceros males (p < 0.05). These results provide crucial insights into the population dynamics and ecological adaptations of shrimp in İskenderun Bay. The findings contribute to understanding the species’ growth characteristics, supporting the development of sustainable fisheries management strategies in the region.

Responses of Fish Zeta Diversity (ζ) to Human Pressure and Cumulative Effects: A Feasibility Study of Fishing Ban Measures in the Pearl River Basin, China

Amid declining fish diversity and human pressures in freshwater ecosystems, robust basin-scale assessments are vital for effective fisheries management. This study collated nearly four decades of fishery yields from the Pearl and Yangtze Rivers to identify conservation priorities in the Pearl River Basin. It introduced a novel cumulative effect indicator based on zeta diversity—a biodiversity pattern metric—integrated with cumulative effects analysis for management decision-making. The research employed a multi-site generalized dissimilarity model to examine the non-linear relationships between fish species composition (ζn) and human pressures, environmental factors, and geospatial variations across elevation gradients. The cumulative effect indicator, reflecting responses to anthropogenic stress when assessing ζ2 (related to β diversity), helped evaluate basins for conservation or restoration needs based on their unique or homogenized biotic communities. The results suggest that ζ diversity in low-elevation sub-basins has a stronger filtering effect on ζ by human pressures than in mid- to high-elevation sub-basins, where community aggregation is more random. The impact varied with diversity aspects (nestedness vs. turnover) and zeta order. A negative correlation between cumulative effects and community uniqueness validated the novel cumulative effect indicator’s effectiveness for guiding restoration in the Pearl River Delta, potential fishing bans, and karst conservation. This approach offers a theoretical basis for prioritizing areas for freshwater fish diversity conservation and fishing restrictions in the Pearl River Basin.

Towards Quota-based Fishery: Current Status and Future Needs of The Quota-Based Fisheries Management in Indonesia

Towards Quota-based Fishery: Current Status and Future Needs of The Quota-Based Fisheries Management in Indonesia

Gaps hindering the objectives of fisheries co-management mechanisms in Sri Lanka

The fisheries industry in Sri Lanka plays a vital role in nutritional and food security, job creation, and foreign revenue earnings. Co-management is an important strategy for sustainable fisheries management, where fishers, government bodies, and other stakeholders work together. This study aimed to identify gaps affecting the achievement of 17 FAO good practice indicators related to social and economic goals and objectives of co-management in Sri Lanka's coastal fisheries sector. A two-stage cluster sampling method was used to select participants: two Fisheries Management Areas were randomly selected from 18 existing areas, followed by three Fisheries Management Committees from each of the chosen Fisheries Management Areas. Data collection involved a structured questionnaire administered to 115 fishers, representing a 40 percent sample of the total membership across six selected Fisheries Management Committees. A desk study of existing laws and regulations, two focus group discussions, and 30 key-informant interviews with officers from the Department of Fisheries and Aquatic Resources, scientists, leading fishermen, and academics were conducted. The study revealed significant gaps affecting the successful implementation of co-management. Key findings include the absence of comprehensive fisheries management and development plans, low participation of women, youth, and other marginalized groups, limited involvement of state and non-state agencies beyond the Department of Fisheries and Aquatic Resources, and weak linkages between co-management programs and economic benefits for fishers. To address these issues, the study recommends prioritizing the development of comprehensive co-management plans, actively involving all stakeholders, including women, youth, and marginalized groups, and creating co-management platforms that accommodate the diverse interests of all stakeholders.

Quota Allocation Policies in U.S. Federal Fisheries Management and Implications for Climate Resilience

ABSTRACTQuota allocation, which divides fishing catch or effort between regions, sectors, subsectors, individuals, and/or seasons, is one of the most important and contentious processes in fisheries management. Quota allocation policies often aim to advance fairness and equity goals by preserving levels of historical participation and access. However, this reliance on historical patterns makes allocation policies vulnerable to climate change, which is shifting the accessibility of marine resources among historical and new participants. Despite this, there is little guidance on best practices for adapting allocation policies to climate change. In the United States, regional flexibility to design locally relevant allocation policies has innovated a diversity of approaches that can be studied for their climate vulnerability and/or adaptivity. Here, we conduct a systematic review of allocation policies used in U.S. federal fisheries (491 stocks, 42 management plans, 8 regions) and a brief review of allocation policies in international fisheries, which we use to identify best practices for climate‐adaptive quota allocation. We find that allocation policies are used to manage 49% of federally managed stocks. Although most policies are based on historical catch, many include features that promote climate adaptiveness, including the ability to transfer quota between states, sectors, or individuals; adjustment of allocations on the basis of current resource distribution or abundance; set aside of quota to support research and experimentation; and gradual phase‐in of policy changes. Ultimately, we provide eight globally transferable recommendations for improving the ability of allocation policies to advance their fairness and equity goals under climate change.

Commercial fishing influences the life histories of fish in the world's largest desert lake.

Lake Turkana, the world's largest permanent desert lake, is an important source of fish for both local consumption and international trade. The growth of Lake Turkana's commercial fishery has increased the risk of overexploiting the lake's fish stocks. Selection pressure from overexploitation of fish stocks often drives shifts in fish life-history traits, including mean length (Lmean), maximum length (Lmax) and size at maturity (Lmat). To assess the life-history indicators of overexploitation in Lake Turkana, we compared the life-history traits of six of Lake Turkana's major commercial fish species from three time periods (1930-1953, 1972-1975, 2010-2022) that represent distinct levels of fishing pressure. These focal species were the African butter catfish Schilbe uranoscopus Rüppell 1832, the elongate tigerfish Hydrocynus forskahlii (Cuvier 1819), Nile perch Lates niloticus (L. 1758), Nile tilapia Oreochromis niloticus (L. 1758), silversides Alestes baremose (Joannis 1835) and wahrindi Synodontis schall (Bloch and Schneider 1801). Heavily exploited species exhibited notable decreases in Lmat as fishing pressure increased, and include A. baremose (29.7% decrease), H. forskahlii (16.4% decrease), L. niloticus (56.1% decrease) and O. niloticus (45.3% decrease). In contrast, lightly exploited species, including S. uranoscopus and S. schall, did not exhibit large declines in life-history traits. Additionally, we used current catch length frequency data for L. niloticus to infer that L. niloticus are currently experiencing overfishing and exhibit signs of the depletion of large 'mega-spawners'. These results suggest that heavy commercial fishing likely drives the observed life-history responses. We suggest that the management of sustainable fisheries in Lake Turkana should focus on gear size restrictions as well as on reducing fishing effort on commercial-sized fish to decrease the probability of overfishing and potential declines of stocks.

The Pragmatic Sceptic: A Practical Approach for Integrating Environmental DNA Into Marine Stock Assessment and Fisheries Management

ABSTRACTThe ‘omics revolution’ has advanced scientific understanding of marine ecosystems and led to a rapid increase in data that can inform species' population structure, distribution, and abundance. Of the 'omics data types, environmental DNA (eDNA) may present the most cost‐effective opportunity for developing quantitative estimates of abundance trends, a key input for stock assessment models. However, eDNA has yet to be widely adopted for stock status determinations within regional fisheries management organisations. We review progress towards addressing key challenges that limited the application of eDNA in marine fisheries management, including advances in (1) the quantitative relationship between eDNA observations and species biomass, (2) reducing false‐negative and false‐positive detections, (3) defining the spatial scale of eDNA, (4) collecting biological data from eDNA surveys, (5) quantifying uncertainty in eDNA surveys, and (6) responding to scepticism of new survey methods. We use a case study with Pacific hake (Merluccius productus) to demonstrate the development of an eDNA index and its direct integration into an age‐structured stock assessment model. Given the many ways in which the field of eDNA has matured, we propose that eDNA can meaningfully inform a range of fisheries management needs, and outline a roadmap for using eDNA in stock assessment models in data‐limited to data‐rich species. A primary impediment to operationalising eDNA as stock assessment model inputs is the lack of interdisciplinary research teams, including geneticists, ecological modellers, and stock assessment scientists, which are necessary to interpret methods and results across scientific disciplines and ensure data are used appropriately.

Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands

The age-based life history of two commercially important parrotfishes (Labridae: tribe Scarinae) and one goatfish (Mullidae) were characterized based on the commercial nearshore fishery in Saipan, Commonwealth of the Northern Mariana Islands. Age, growth, reproduction, and mortality were derived from fishery-dependent samples using sagittal otoliths and gonads for the stareye parrotfish Calotomus carolinus, pacific bullethead parrotfish Chlorurus spilurus, and yellowfin goatfish Mulloidichthys vanicolensis. All three species had short lifespans of 10 years or less, with a maximum age of 4 years for C. carolinus, 10 years for C. spilurus, and 7 years for M. vanicolensis. All three species had a fast initial growth to terminal body sizes, early maturation, and spawned throughout the year. The age-based demographic information presented here can be used to inform future stock assessments, fisheries management, and population models.

Panmictic Panacea? Demonstrating Good Practices for Developing Spatial Stock Assessments Through Application to Alaska Sablefish (Anoplopoma fimbria)

ABSTRACTMarine species and associated fisheries demonstrate complex spatial dynamics driven by biological, ecosystem and socioeconomic factors and integrating these spatial dynamics into stock assessment models can improve fishery management advice. While preliminary good practices for developing spatial stock assessment models have been proposed, comprehensive demonstrations applying these practices remain limited. Drawing on these good practices, we provide an end‐to‐end demonstration of developing a spatial stock assessment using Alaska sablefish (Anoplopoma fimbria). Our demonstration emphasises the utility of high‐resolution data analysis and conceptual models for informing key model structure decisions, the joint development of spatial and spatially‐aggregated models to enhance understanding of population dynamics, and the need for further guidance on integrating tagging data and diagnostic tools in spatial assessments. Spatial models highlighted regional differences in sablefish biomass, recruitment and age structure, but total population estimates generally aligned with outputs from spatially aggregated models. Moreover, the spatial model identified ontogenetic movement patterns for this highly mobile species. Overall, the spatially aggregated model for Alaska sablefish is likely adequate for management advice, but periodic spatial model updates could offer insights into spatial dynamics and regional depletion levels. Thus, we recommend concomitant use of both models: spatially aggregated models for informing population‐wide status, and spatial models for informing spatial fishery dynamics and local depletion. The sablefish application represents one of the first implementations of a spatial stock assessment using recently proposed good practices, serving as a valuable guide for future practitioners by underscoring critical decision points and analyses to address them when developing spatial stock assessments.

Conflict Between Conservation and Livelihood: Gender‐Specific Impacts of a Fishing Ban on Erhai Lake, China

ABSTRACTFishing bans are an important regulation for fishery management, but the gender‐specific impact of fishing bans has rarely been studied on traditional fishing communities. We aimed to quantify how women and men from a traditional Bai fishing community around Erhai Lake, China, were affected by a year‐round fishing ban implemented in 2017. Using a mix of quantitative and qualitative research methods, we quantified gendered impacts of the fishing ban on various aspects of life. The fishing ban excluded women from fishing and also decreased their household income, which increased women's burden to manage household finances. Poorer women were affected more than better‐off women because they had fewer resources. Men fishers indulged in mahjong gambling to release their stress during the fishing ban, thereby increasing women's stress. Our findings highlight the importance of intersectional gender analysis and coping strategies of fishers when analyzing socioeconomic effects of fishing bans.

Fishery, Growth and Reproductive Biology of Metapenaeus affinis (Decapoda, Penaeidae) in the Iraqi waters

The study evaluated the fishery, growth and reproductive biology of the Jinga shrimp (Metapenaeus affinis) in Iraqi waters from November 2022 to October 2023. The monthly shrimp landings from Iraqi marine waters ranged from 57 tons in December 2022 to 407 tons in September 2023, with an annual value of 3,515 tons. 8,021 individuals of M. affinis, ranging from 2.0 to 15.6 cm, were collected from the East Hammar marsh and Iraqi marine waters. The length-weight relationship indicated that males and females exhibited negative allometric growth patterns, with a significant difference between them. The mean values of the relative condition factor were 0.98±0.037 and 1.02±0.043 for males and females, respectively, referring to the healthy condition for both sexes. The growth model for the species was Lt= 16.3 (1- exp (-0.92 (t+0.084))). The overall sex ratio (male: female) was 1:1.41. The length at first maturity (Lm50) was 8.2 cm. The gonadosomatic index (GSI) values fluctuated from 2.14% in June to 4.34% in April for females of M. affinis. These results can assist in fisheries management and conservation of the shrimp species in Iraqi waters.