Explore the vast range of titles available.

Our general purpose is to support the use of known-biomass production models (KBPMs), illustrating their usefulness by addressing the evolution of surplus production (SP) over time and the factors affecting it (e.g. environment). We also demonstrate the utility of KBPMs for multispecies management objectives or for estimating maximum sustainable yield reference points without a stock recruitment function, among other worthwhile applications. To do so, we present different uses of KBPMs, illustrating their application on demersal species in the International Council for the Exploration of the Sea (ICES) area, specifically for megrim, white anglerfish and European hake stocks. The proposed analytical approach involved fitting single-species and multispecies KBPMs, conducting retrospective analyses and assessing the effects of environmental variability on SP. The findings show that, in general, stock SP increased after a decline in biomass and SP, except for white anglerfish in the southern area. Megrim stocks are the least productive, while hake and northern anglerfish are the most productive. Retrospective analysis revealed SP shifts in northern hake stock for reasons other than biomass variability. Hence, the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation (AMO), two key climate variability modes in the North Atlantic, were tested for their links to SP, revealing a positive connection between SP and AMO, although further research is necessary. Beyond the specific results of our particular KBPM application, our main conclusion is that KBPMs can serve as a tool complementary to more complex assessment models for resolving unaddressed issues and crosschecking available assessment results.

Maximum sustainable yield reference points (MSY-RPs) are usually calculated assuming spawner-recruitment relationships (SRR) and population dynamics of the stock. However, due to the difficulty of estimating SRR, the uncertainty in MSY-RPs is often too large to be put into practice. Therefore, based on the concept of maximum–minimum yield (MMY), fishing mortality (F) that gives %SPR (spawner biomass per recruitment [SPR] at a given F relative to SPR in the absence of fishing) of 30–50% (F30-50%SPR) is often used as a proxy of FMSY (F that maximizes the long-term catch). In this study, we estimated F%SPRMMY (F expected to produce %SPR at MMY) for 30 stocks of Japanese fishery resources based on the life-history parameters of the stocks and steepness assumptions derived from meta-analysis. Our results showed that %SPRMMY ranged from 23% to 62% (excluding 86% of Scomberomorus niphonius), depending on the stock and the assumed steepness scenario. If the fish were caught under F%SPRMMY, at least 70% of the MSY could be expected in Japanese fishery resources. When compared with the %SPRMSY for the 15 stocks estimated through Japanese fishery stock assessment, %SPRMMY were similar, or often larger. %SPRMMY can be considered a precautionary value, reflecting the uncertainty of SRR.

Abstract The intensive fishing and lack of data for squid fisheries in Belitung waters have increased the risk of stock population decline, which could lead to large economic losses. Comprehensive studies on the biological aspects and stock status of squid were crucial to developing some management recommendations. This study investigated several population ecological characteristics (size distribution, length-weight relationship, condition factors, maturity stages, length at maturity, and growth parameters), the stock status, and the biological reference points of mitre squid (Uroteuthis chinensis Gray, 1849) in Belitung waters. The squid’s biological data were collected from August 2023 to March 2024. The stock status was investigated by several approaches, including length-converted catch-curve (LCC), yield per recruit (YPR) analysis, and length-based spawning potential ratio (LB-SPR). This study revealed that the mean size of male and female squid captured by squid jig was 16.22 ± 6.72 cm and 14.23 ± 3.65 cm (Mean of mantle length ± standard deviation), with the length at first maturity (Lm50) of 19 cm for males and 12 cm for females. Female gonadally mature squid were found throughout the year, with the largest proportion in January (93%). The overfishing condition of U. chinensis has occurred based on the current exploitation level for male (Ecur: 0.63; Fcur: 2.61 year-1) and female (Ecur: 0.72; Fcur: 4.39 year-1) that exceeds both the optimal exploitation rate (Eopt=0.5) and the fishing mortality given the maximum yield per recruit (Male Fmax: 2.08 year-1; Female Fmax: 3.35 year-1). Recruitment overfishing has also occurred based on the current spawning potential ratio of 18%. Reducing the fishing trips by 24%, applying a season closure in January, and enlarging the selectivity to 15 cm were recommended to raise the squid stock and ensure the sustainability of squid fisheries in Belitung waters. Resumo A pesca intensiva e a falta de dados sobre a pesca de lula nas águas de Belitung aumentaram o risco de declínio da população dos estoques, o que poderia levar a grandes perdas econômicas. Estudos abrangentes sobre os aspectos biológicos e o status dos estoques de lula foram cruciais para a formulação de algumas recomendações de manejo. Este estudo investigou várias características ecológicas da população (distribuição de tamanho, relação comprimento-peso, fatores de condição, estágios de maturidade, comprimento na maturidade e parâmetros de crescimento), o status do estoque e os pontos de referência biológicos da lula-mitra (Uroteuthis chinensis Gray, 1849) nas águas de Belitung. Os dados biológicos da lula foram coletados de agosto de 2023 a março de 2024. O status do estoque foi avaliado por meio de diversas abordagens, incluindo curva de captura convertida pelo comprimento (LCC), análise de rendimento por recruta (YPR) e razão potencial de desova baseada em comprimento (LB-SPR). Esse estudo revelou que o tamanho médio das lulas machos e fêmeas capturadas pelo gabarito de lula foi de 16,22 ± 6,72 cm e 14,23 ± 3,65 cm (média do comprimento do manto ± desvio-padrão), com o comprimento na primeira maturidade (Lm50) de 19 cm para os machos e 12 cm para as fêmeas. Lulas fêmeas com gônadas maduras foram encontradas durante todo o ano, com maior proporção registrada em janeiro (93%). A condição de sobrepesca da U. chinensis ocorreu com base no nível de exploração atual para machos (Ecur: 0,63; Fcur: 2,61 ano-1) e fêmeas (Ecur: 0,72; Fcur: 4,39 ano-1) que excede a taxa de exploração ideal (Eopt=0,5) e a mortalidade por pesca, considerando o rendimento máximo por recruta (Fmax masculino: 2,08 ano-1; Fmax feminino: 3,35 ano-1). A sobrepesca de recrutamento também ocorreu com base na atual taxa de potencial de desova de 18%. A redução das viagens de pesca em 24%, a aplicação de um defeso em janeiro e a ampliação da seletividade para 15 cm foram recomendadas para aumentar o estoque de lula e garantir a sustentabilidade da pesca de lula nas águas de Belitung.

Biological reference points are key quantities provided by stock assessments and used in fishery management for evaluating fishery status and setting future catch levels. For many fisheries worldwide, biological reference points are based on the spawning potential ratio (SPR), which measures per-recruit reproductive output as a function of the fishing rate relative to that when fishing is absent. SPR depends on the biological characteristics of the stock, which in turn can be influenced by the environment. A fishing rate based on SPR is often used as a proxy for the fishing rate that provides maximum sustainable yield. Here, we evaluate variability in the fishing rate (F40) that provides an SPR of 40%, a commonly used limit reference point, given plausible variability in biological characteristics. Using eight case-study species from marine waters off the southeast United States, we consider both simple random variability and directional variability, both of which might result from climate change. We test the sensitivity of F40 to various life-history traits and compute distributions of F40, given the expected variability in those traits. Based on those distributions, we evaluate the probabilities of overfishing given a target fishing rate (here, 75%F40) that is based on prevailing conditions without considering future variability in F40, consistent with common, current practice. Analyses also considered an SPR of 30% and 50% to evaluate the generality of conclusions. Results support that SPR-reference points are generally robust to plausible levels of variability in life-history traits that might be induced by environmental nonstationarity and that associated target fishing rates can provide meaningful buffers to prevent overfishing.

This study investigates the age, growth, and mortality of the common pandora (Pagellus erythrinus) in the Central Aegean Sea, providing critical insights into its population dynamics and sustainability. A total of 589 specimens were analyzed, identifying nine age cohorts with mean total lengths ranging from 13.18 cm to 32.94 cm. Growth parameters, estimated using the von Bertalanffy growth model, yielded an asymptotic length (L∞) of 39.53 cm and a growth coefficient (k) of 0.16 year−1, indicating moderate growth rates. The population exhibited non-isomorphic growth (b = 2.49, R2 = 98.4), suggesting slower weight gain relative to length. Mortality estimates indicated natural mortality (M) at 0.321 year−1, total mortality (Z) at 0.52 year−1, and fishing mortality (F) at 0.2 year−1, resulting in an exploitation rate (E) of 0.38. The fishing mortality at maximum sustainable yield (FMSY) was estimated at 0.33, with an exploitation rate at MSY (EMSY) of 0.51, suggesting that the population is currently harvested sustainably but close to the threshold of overexploitation. These findings provide essential reference points for fisheries management and highlight the need for continuous monitoring to ensure the long-term sustainability of P. erythrinus in Greek waters.

Ecosystem-based fisheries management (EBFM) emphasizes sustainability at multiple levels of organization beyond single target species. Therefore, biological reference points (BRPs) for aggregated groups are required, which optimize yields while preventing overexploitation of individual species. We evaluate the tradeoffs between yield and biodiversity objectives for a wide range of aggregation strategies using multispecies surplus production models and comparing 2 simulated fish communities. We simulated population trajectories with an operating model de - tailing predation and competitive interactions for all individual species within each community, and with additional stochastic environmental variability for one community. Species trajectories were then aggregated by functional feeding guild, taxonomy, habitat association, size class, and at the entire community level. We estimated production parameters and BRPs (e.g. maximum sustainable yield, MSY) using a simple assessment model applied to each aggregated time series, then we applied the MSY fishing rates to each simulated community as alternative fishing strategies and compared equilibrium biomass and yield under each strategy. We were able to define multi-species reference points to meet both yield and biodiversity objectives across full system, taxonomic, habitat, feeding, and size-based aggregations. Species complexes were best able to meet both objectives when species with broadly similar productivity, environmental sensitivity and species interactions were aggregated into the complex. The impacts of simulated environmental variability on BRPs were substantial for certain species and aggregates, so including the combined impacts of environmental variation and species interactions in precautionary reference points appears critical to EBFM.

In Europe, implementation of sustainable fisheries management has been reinforced in the latest common fisheries policy, and presently marine fish stocks are mostly managed through assessment of their exploitation and ecological status compared to reference points such as Maximum Sustainable Yield (MSY). However, MSY and its associated fishing mortality rate FMSY are sensitive to both stock characteristics and environment conditions. In parallel, climate change impacts are increasingly affecting fish stocks directly and indirectly but might also change the exploitation reference points and the associated level of catch. Here we explored the variability of MSY reference points under climate change by using a multi-species model applied to the Eastern English Channel, a highly exploited semi-continental sea. The spatial individual-based OSMOSE explicitly represents the entire fish life cycle of 14 species interacting through size-based opportunistic predation. The model was first parameterized and run to fit the historical situation (2000-2009) and then used to assess the ecosystem state for the 2050-2059 period, using two contrasting climate change scenarios (RCP 4.5 and RCP 8.5). For each condition, a monospecific MSY estimation routine was performed by varying species fishing mortality independently and allowed estimation of reference points for each species. The FMSY estimated with OSMOSE were mostly in accordance with available values derived from stock assessment and used for fishing advice. Evolution of reference points with climate change was compared across species and highlighted that overexploited cold-water species are likely to have both MSY and FMSY declining with climate warming. Considering all species together, MSY under RCP scenarios was expected to be higher than historical MSY for half of them, with no clear link with species temperature preferences, exploitation status or trophic level, but in relation with expected change of species biomass under climate change. By contrast, for 80% of cases FMSY projections showed consistent decreasing pattern as climate conditions changed from historical to RCP scenarios in the Eastern English Channel. This result constitutes a risk for fisheries management, and anticipation of climate change impacts on fish community would require targeting a smaller fishing mortality than FMSY to ensure sustainable exploitation of marine stocks.

Cephalopholis sonnerati , a grouper species, is a primary target of the export market in Sri Lanka. Significant harvesting occurred between 2015 and 2017, driven by the Live Reef Food Fish Trade in addition to small-scale coastal fisheries. Nevertheless, no scientific studies have assessed the sustainability of the fishery or the status of C. sonnerati populations in Sri Lankan waters. To address this gap, we utilized length-based, data-limited approaches to assess the sustainability of the fishery for C. sonnerati in eastern and western coastal waters in Sri Lanka. The von Bertalanffy growth parameters were separately estimated for the western and eastern populations: L ∞ = 63.1 and 62.4 cm ( TL ); K  = 0.26 and 0.24/year; mean M  = 0.50 and 0.47/year; and L 50  = 36.0 and 43.5 cm ( TL ). Length-based indicators (LBIs) and F max suggest that the fishery for C. sonnerati was operating at MSY levels. However, LBIs for the conservation of immature and mature individuals for both populations fell below the expected levels, indicating fishery unsustainability. The length-based spawning potential ratios (LBSPRs) of the western and eastern coastal populations were estimated to be 24% and 13%, respectively, below the expected reference points of the LBSPR. Furthermore, the models showed size selectivity estimates at 50% and 95% were lower than the estimated sizes at L 50 . In conclusion, it is suggested that C. sonnerati populations in western and eastern coastal waters are presumably at risk of overexploitation by growth and recruitment overfishing, highlighting the need for effective management and conservation plans.

The objectives of this study were to determine the rates of natural mortality (M), fishing mortality (F), total mortality (Z), the exploitation rates (E), as well as the biological reference points (BRPs) and the annual removal rates (R) of the crocodile shark, Pseudocarcharias kamoharai, in the Ecuadorian Pacific. Thirty similar and different models were applied to determine all these rates. These equations were obtained from studies on teleost and chondrichthyan fish. The biological parameters, including age, growth, longevity, and reproduction, were obtained from the specialized literature based on the biology of P. kamoharai in Ecuadorian waters. These biological parameters were used in all the models considered here. The M estimations were 0.14 to 0.28 based on six models for chondrichthyans and osteichthyes. These values were similar to the six algorithms designed for cartilaginous fish, ranging from 0.16 to 0.35; for this reason, these mortality rates were considered low. The Z values ranged from 0.08 to 0.51; however, they were not considered given that the three estimations were less than M, and only the Z = 0.51 was considered. Given that Z = 0.51 and M = 0.24, an F = 0.27 was obtained by subtraction, indicating a low mortality by fishing. E had values between 0.21 and 0.53, which indicated overexploitation that exceeded the Eopt = 0.50 value. The obtained BRPs were Fopt = 0.10 and 0.12 and Flim = 0.16, which showed that the optimal fishing levels (best possible capture) to achieve long-term sustainable exploitation of the stock encompass 10 to 16% of the fishing effort applied for this species. However, the F surpassed this prudential range. The annual removal percentage (R = 21%) demonstrated that 21% of the population was being removed. Based on the biology and ecology of this species, all models applied in this study showed that P. kamoharai had low natural and fishing mortality rates and moderate total mortality; its exploitation rate exceeded the fishing limits. These values and their life history traits indicated that this shark species cannot tolerate any fishing level without threatening its populations.

The pelagic thresher shark is among the most heavily exploited shark species in the commercial fisheries of the tropical Indo‐Pacific oceans. Despite this severe exploitation, little is known about pelagic thresher population dynamics, particularly the species' life history traits, and overall stock status. The pelagic thresher exhibits slow growth and extremely low fecundity, indicating the need for reassessment of the population status of this globally threatened shark. Because information on catch and effort of this bycatch species is scarce, several data‐limited methods—quantitative demographic methods, per‐recruit analysis, and risk assessment—were employed in this study to provide an accurate measurement of the status of pelagic thresher shark stocks. For each sex, the composite risk assessments indicated that the probability of the current fishing mortality increasing beyond any level of yield‐per‐recruit (YPR) was approximately zero given the biological reference points (BRPs). Moreover, the current spawning potential ratio (SPR) was found to be significantly below the target reference point of SPR60%, but slightly above the limit reference point of SPR40%. However, because SPR‐based BRPs are much less sensitive to input parameter uncertainties than YPR‐based BRPs, results derived from the SPR model are more suitable for species management. Management strategy simulations based on demographic two‐sex models indicated that without mortality from fishing, female pelagic threshers have a higher population growth rate than males. However, the stock status of female pelagic thresher shark is poorer than that of males under current conditions. The findings suggest that sex‐specific management decisions must be made to achieve the sustainable utilization of this species. Overall, both the sex‐specific per‐recruit and demographic models determined that recruitment overfishing has occurred in the female pelagic thresher population of the Northwest Pacific Ocean, indicating that close monitoring of female sharks is urgent and necessary to ensure that stocks remain sustainable. Box plots for the population growth rate of the pelagic thresher in various scenarios. The specific objectives of this study are to estimate current and sustainable fishing mortality, biological reference points, and evaluate management strategies for the pelagic thresher shark stocks in the Northwest Pacific Ocean. The results obtained in this study can provide valuable information on fishery management and conservation to better manage the pelagic thresher population in the Northwest Pacific region, and this approach can be easily applied to other fish species that lacked sufficient time‐series of abundance index data.