ABSTRACT Environment‐recruitment relationships often break down over time. This can occur because of spurious results from testing numerous environmental variables in the original analyses or from relative changes in the importance of specific environmental drivers over time. An environment‐recruitment model was developed for the Newfoundland and Labrador capelin stock, but the relationship first weakened with the addition of new data and then recently broke down. We hypothesized that the thermal and wind parameters in the original environment‐recruitment model were now less important for recruitment dynamics following a stock collapse in 1991 due to the observed change in stock demographics, while other mechanisms like timing of spawning and annual climate conditions may be more important. Furthermore, three different measures of age‐2 recruitment were used in the original model and subsequent re‐testing of the environment‐recruitment relationships, which may have instigated a spurious breakdown of this relationship. Using a consistent empirical measure of age‐2 recruitment for the 1983–2022 year‐classes, an earlier timing in peak spawning predicted higher age‐2 recruitment, although only a moderate level of variability ( R 2 < 40%) was explained. The timing of spawning has been persistently delayed since the stock collapsed in 1991, which has had a profound impact on stock dynamics. This study demonstrates the importance of renewed and frequent reassessment of prior knowledge of stock dynamics and environment‐recruitment relationships, especially when dramatic changes in stock dynamics or ecosystem regime shifts are observed.
ABSTRACT Jonah crab and Atlantic rock crab in the United States are currently assessed by National Oceanic and Atmospheric Administration climate change vulnerability assessments under the category Cancer crabs due to a dearth of species‐specific information across the attributes assessed. These species are frequently bycatch in the American lobster fishery and have low landed volume in comparison to larger Northeast US commercial fisheries. Here, we developed species distribution models using abundance, bottom temperature, and bottom salinity from Northeast Fishery Science Center Bottom Trawl data and calculated species‐specific environmental suitability indices. We used interpolated data to hindcast (1992–2024) environmental suitability in the five Jonah crab stocks for each species. Then, using similar methods, environmental suitability was forecasted from bottom temperature and bottom salinity conditions from 2075 to 2094 under RCP 8.5 climate conditions. This analysis found that Jonah crab occupies a narrow, stable niche, with optimal temperatures of 9°C–12°C in both seasons and habitat 150–350 m deeper than Atlantic rock crab, while Atlantic rock crab tolerates far larger swings, with the OSNE stock shifting optimal temperature by 11°C (5°C to 16°C) and salinity by 7 units between spring and fall. By identifying these differences, we show that Jonah crab's narrower thermal and salinity tolerance likely makes it more sensitive to climate change than the broadly tolerant Atlantic rock crab, refining species‐specific inputs for climate change vulnerability assessments and each species' potential as a long‐term fishery target.
ABSTRACT Fisheries management often relies on single‐species assessments, overlooking multispecies dynamics while facing the added challenge of nonlinear environmental variability. Marine landings of most commercially exploited species in the Southwestern Atlantic have declined for decades and are projected to decrease further under climate change, as ocean warming is expected to reduce fisheries catches and revenues. Despite these trends, multispecies studies linking regional landings to environmental forcing remain scarce. Addressing this gap, we propose an integrated approach to examine multiscale environmental influence on fisheries landings within the Argentinean–Uruguayan Common Fishing Zone, a complex hydrographic region strongly influenced by the Río de la Plata discharge. We applied time‐series alignment and latent factor modeling to identify common patterns across multivariate landing series. These patterns served as response variables in lagged generalized linear and additive models, incorporating as predictors: riverine runoff, sea surface temperature, salinity, and turbidity, wind mixing, and large‐scale climatic indices such as the El Niño–Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Southern Oscillation Index (SOI). Time‐lagged analyses show that environmental forcing at local and basin scales explains much landings variability. Turbidity and salinity were the most consistently retained variables, while the best‐fitting model (82% deviance explained) incorporated the combined effects of SAM and turbidity. Our findings demonstrate that diverse fisheries landings can be summarized into common multivariate patterns, which in turn can be linked to multiscale environmental forcing. This provides a robust basis for climate‐informed management, supporting a transition from isolated single‐species assessments to integrated multispecies frameworks.
ABSTRACT Pacific saury ( Cololabis saira ) is an ecologically and commercially important small pelagic species in the northwestern Pacific, where fishing grounds have shifted markedly eastward in recent years. However, the role of early‐season oceanographic variability in shaping this redistribution remains poorly understood. Using catch records, Automatic identification systems‐derived fishing hours, vessel registry data, and nighttime light (NTL) observations, we examined fishing activity during 2012–2020 and linked fishing‐ground displacement to environmental variability and Kuroshio Extension system (KES) hydrographic conditions. NTL radiance outperformed CPUE and fishing hours in representing environmentally structured fishing‐ground variability, highlighting its value for tracking transboundary displacement in this light‐luring fishery. The optimal random forest model identified mixed layer depth, sea surface salinity, phytoplankton carbon, and sea surface temperature (SST) as the dominant predictors. Radiance‐weighted centers of gravity revealed especially strong eastward displacement in 2019–2020. Early‐season (May–July) displacement was strongly associated with annual displacement, indicating that the annual fishing‐ground pattern was largely preconditioned during the early‐season. Among the dominant environmental variables, SST displacement in the traditional fishing grounds showed the strongest relationship with the eastward shift. Years with longer Kuroshio Extension fronts and higher regional mean KE showed greater eastward displacement, indicating an association between early‐season KES‐related hydrographic variability, thermal reorganization of the traditional fishing grounds, and eastward redistribution. These findings demonstrate the value of nighttime fishing radiance for detecting environmentally structured fishery redistribution and suggest that early‐season KES‐related hydrographic variability is an important oceanographic context for the recent eastward shift of saury fishing grounds.
We developed and evaluated a fishery-dependent catch-per-unit-effort (CPUE)-based proxy index for juvenile Japanese anchovy (Engraulis japonicus) recruitment-related variability in the southeastern coastal waters of Korea. The proxy was constructed from bimonthly CPUE of the smallest juvenile size class (20-40 mm) in the anchovy drag-net fishery during 1992-2018. We reassessed lagged associations with large-scale climate indices and local coastal variables using wavelet coherence, autocorrelation diagnostics, structural-equation/path-regression diagnostics, and generalized linear/additive modeling sensitivity analyses. Wavelet analysis used a bimonthly time grid (dt = 2 months), 1000 Monte Carlo simulations, false-discovery-rate correction, and robustness checks based on Fourier-randomized surrogates, STL-residual series, and AR(1)-prewhitened series. Raw white-noise wavelet analyses reproduced localized seasonal-to-annual coherence, particularly for local temperature, salinity, log10-transformed precipitation, and the vertical temperature-difference index. However, multiyear PDO/MEI coherence was not stable after FDR correction or under autocorrelation-sensitive robustness checks. We therefore interpret multiyear climate associations as exploratory low-frequency associations rather than direct cohort-level biological delays. Phase-dependent path-regression diagnostics indicated heterogeneous association structures across PDO phases, with the most consistent short-lag signal involving temperature. Seasonal log-linear sensitivity models provided moderate explanatory power on the log scale, with adjusted R 2 values of 0.558, 0.539, and 0.523 for the August, October, and August-October seasonal proxy models, respectively. Overall, the analysis supports using the CPUE series as an operational fishery-dependent proxy for recruitment-related variability, while emphasizing that the inferred lagged relationships are statistical associations requiring cautious interpretation and future validation with fishery-independent surveys.
Marine waters are becoming warmer and acidified and experiencing more intense and longer heatwaves under climate change. These changes are already impacting marine ecosystems and seafood production, which are vital for supporting food security and economic productivity. For Australia, a national-scale assessment of exposure to climate hazards is needed to support climate-resilient ecosystem management across one of the world's largest exclusive economic zones. Commercial fishing relies on healthy ecosystems and is one of Australia's most important sectors in terms of cultural identity and regional value. However, Australian fisheries and aquaculture are increasingly exposed to climate-driven changes in ocean conditions, creating substantial risks for marine ecosystems, seafood production and coastal economies. We assess the exposure of Australia's seafood sector to climate change using high-resolution climate projections and ecosystem model outputs under three global warming levels (1.5 degrees C, 2 degrees C and 3 degrees C futures). Our findings reveal that the entire Australian exclusive economic zone is exposed, with cumulative exposure highest for regions with a large continental shelf. The biomass available to fisheries is projected to decline. Negative impacts from climate change are generally expected for fisheries and aquaculture production. Despite some evidence of adaptation, uneven adaptive capacity across sectors and jurisdictions presents challenges for climate resilience. This study underscores the urgency of global mitigation efforts to reduce risk, coordinated adaptation strategies, improved coastal hazard modelling and ecological risk assessments to safeguard the future of fisheries and aquaculture industries under climate change.
ABSTRACT The Bay of Bengal (BoB) is a vital marine ecosystem that sustains diverse fisheries and significantly contributes to regional food security. This study investigates the spatiotemporal variability of marine primary productivity in the northern BoB and its environmental drivers—sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen (DO), and chlorophyll‐a (Chl‐a). Multiseasonal Sentinel‐3 OLCI and SLSTR satellite datasets from 2024 were analyzed using correlation analysis, multiple linear regression, and ARIMA time‐series forecasting to assess how hydrographic variability influences phytoplankton dynamics. The results show that winter exhibits the highest phytoplankton biomass (Chl‐a up to 1.50–3.02 mg m −3 ), driven by low SST, elevated DO, and freshwater discharge that enhance vertical mixing and nutrient availability. Statistical analysis revealed that SST appears to be a significant driver during the monsoon ( p = 0.012), whereas DO showed a significant association with productivity ( p = 0.002), which may reflect favorable environmental conditions rather than a direct biological causation as phytoplankton produce oxygen. During summer, stratification may have contributed to the suppression of productivity, and a multivariate statistical link ( R 2 = 0.78) reflected combined effects of SST, SSS, and DO. ARIMA forecasting indicated a short‐term increase in Chl‐a (1.62–2.28 mg m −3 ), suggesting continued favorable production trends. Seasonal hydrographic variability therefore regulates habitat suitability, influencing spawning, feeding, and migration of hilsa, sardine, anchovy, mackerel, and juvenile tuna. Integrating satellite‐based monitoring with predictive modeling supports climate‐resilient fisheries management and reinforces ecosystem‐based governance. The outcomes contribute to multiple sustainability targets, including SDG 14 (Life Below Water), SDG 13 (Climate Action), SDG 2 (Zero Hunger), and SDG 1 (No Poverty).
Effective monitoring of pelagic fish populations is crucial for sustainable fisheries management. Traditional vessel-based acoustic surveys often lack the temporal coverage needed to capture dynamic fish distribution and behaviour in response to short-term environmental drivers, such as gales. This study evaluates the reliability of an active-acoustic glider for monitoring European anchovy (Engraulis encrasicolus) schools in the south-eastern Bay of Biscay, Spain, aiming to complement existing vessel surveys. During the 2022 JUVENA sampling campaign (September-October 2022), concurrent glider and vessel acoustic data were collected. A novel glider-adapted protocol for acoustic data processing was developed, revealing high consistency between both methodologies. Glider observations successfully captured anchovy school spatial displacement in response to a gale event. Anchovy exhibited a coastward migration of 4 to 6 km/day, which is two to three times faster than under stable conditions. This coincided with an initial intense episode of deepening (25 to 45 m) of the thermocline, accompanied by a gradual decrease in its depth during the entire campaign. Although the maximum depth of anchovy remained at 30 m, their vertical distribution shifted towards the surface during the gale and progressively deepened again afterwards, remaining above the thermocline. This study showcases a cost-effective observational strategy for extended, uninterrupted monitoring, demonstrating the high potential of glider-mounted echo sounders to enhance our understanding of fish distribution and behaviour in challenging conditions. Although further refinement of acoustic processing protocols and coordinated vessel-glider campaigns are explored in this paper to optimize future missions, the configuration considered constitutes a robust base.
The persistently complicated age structure of sockeye salmon (Oncorhynchus nerka) populations is intriguing. There is a variety of ages, and each age describes the number of winters spent as a free-living fish in freshwater and then the number of winters spent at sea. I used multiple linear regression analysis to test the influences of total female and age-specific female spawner abundances and prey, predator and competitor abundance/biomass on return for each of the 18 natural populations of sockeye salmon in the Fraser River, Canada watershed. I found that return variability was best explained age-specifically and that age-specific female spawner abundance had the dominant effect on return in all cases. Prey, predator and competitor biomass contributed to explaining return variability. Pink salmon (Oncorhynchus gorbuscha) biomass in the Gulf of Alaska exerted the dominant secondary effect. Explanations were unique within and between populations.
The biomass of Japanese sardine and Japanese anchovy is generally considered to cyclically fluctuate in response to climate-related oceanic changes such as Pacific decadal oscillation (PDO). However, little is known about how their spatial ecology changes in relation to the periodic oceanic changes. In particular, the spatial distributions and responses to changes in water temperature of both species, along with shifts in PDO and abundance, are unclear. To reveal the spatiotemporal dynamics in relation to biomass fluctuation and PDO, we estimated the densities, the spatial distributions and thermal niche of both species in the western North Pacific during autumn from 2005 to 2020, using spatiotemporal models. The results indicated that the sardine abundance increased, whereas their distribution pattern was relatively stable during the study period. In addition, their estimated thermal niche (the estimated temperatures associated with their distributions using spatiotemporal models) did not change across PDO phases. In contrast, Japanese anchovy exhibited a notable shift in its distribution pattern from offshore to coastal regions of the Japanese archipelago and a change in their thermal niche over the study period. The present study suggests that temporal variability in the thermal niche is key to explaining species-specific differences in distribution shifts under environmental change. This insight will help improve the projection accuracy of distribution shifts and enhance assessments of climate change impacts on population dynamics of fish species.
Marine fish commonly move across distinct habitats throughout their lifetimes, particularly during larval stages, when they are particularly difficult to track. Such transitions are necessary as environmental demands and predation pressures change dramatically with increases in body size. Fish larvae suffer high natural mortality rates, and varying environmental experiences during early life can significantly impact population demographics. Understanding the nature of habitat use, habitat connectivity and ontogenetic timing of habitat transitions is therefore key to establishing effective management practices covering whole life histories. Tracing individual movements of tiny larvae is impossible using conventional tagging approaches. However, otolith chemistry is an attractive alternative where movements occur across suitable chemical gradients. The stable isotope composition of oxygen in otolith aragonite is a valuable tracer, predictably related to widely measured and/or modelled ocean variables (temperature and salinity). Emerging high-resolution analytical methods enable larval otolith subsampling and the generation of time-resolved isotopic records that potentially reveal larval movements. However, such analyses are logistically challenging and costly, preventing their routine use. A priori determination of when such approaches are likely to generate useful information would enable tailored and cost-effective design for high-resolution otolith isotope projects. Here, we develop isotope-enabled particle drift models to predict whether high-resolution otolith analyses of northeast Atlantic mackerel (Scomber scombrus) larvae have the potential to discriminate among potential spawning origins and associated larval drift trajectories. Larval drift simulations revealed distinct drift patterns associated with four spawning areas: South, West 1, West 2 and the North Sea. Drift pathways and timescales varied significantly between these regions, with larvae in the South remaining near natal spawning areas, while those in the West 1 and West 2 regions exhibited more complex and extensive northward movements. Predicted otolith delta 18O values associated with these drift trajectories differed significantly between some spawning areas, with higher values observed in West 1 and West 2 compared with the North Sea. We identify key regions of the otolith (corresponding to periods of drift) most likely to discriminate among spawning origins, and therefore potentially focussing targeted high-resolution analyses. Our results suggest that a combination of low-resolution and high-resolution otolith sampling could effectively discriminate between different spawning areas and improve our understanding of larval drift patterns. Our coupled model approach is directly transferrable to species with pelagic larval stages and may help to focus resources on species and regions where larval drift questions are reasonably tractable using stable isotope tracers.
Japanese anchovy (Engraulis japonicus) is the most abundant fish in the East China Sea (ECS) and an important fishery resource throughout its life stages. Using samples collected along the ECS shelf-break in April over a 22-year period (2001-2022), we examined the horizontal distribution and interannual variability of larval density (mean standard length: 13.8-19.8 mm). High larval densities consistently occurred in the northern ECS off western Kyushu Island, corresponding to the egg distribution observed in March. In the southern ECS (south of 29 degrees 30 ' N), larvae were primarily distributed along the 100 m isobath. Considering the distribution of eggs and adults in March, these larvae likely originated from local spawning by mature adults present in the region during early spring, potentially including individuals associated with the southward overwintering migration. A substantial proportion of larvae occurring in the southern ECS may recruit to the southern ECS shelf before being transported to the northern ECS. Interannual variations in larval density were not related to habitat conditions (temperature, salinity, or chlorophyll a concentration) but were positively correlated with egg production in March, a proxy for spawning adult biomass. This indicates that variability in larval density is more closely associated with adult biomass than with larval habitat conditions at the spatial and temporal scales considered in this study. Despite differences in the spawning origin, larval density showed a significant positive interannual correlation between the northern and southern ECS, suggesting that adult biomass, spawning timing, and early survival conditions exhibit consistent interannual variability across these sub-areas.
This study examines the distribution, reproductive biology, and trophic strategies of three deep-sea gadiform species (Phycis blennoides, Trachyrincus scabrus, and Mora moro) in the Balearic Basin (western Mediterranean). All three showed a depth-related size trend, but with distinct spatial distributions and life cycles. P. blennoides and T. scabrus were mainly found along the mainland slope, whereas M. moro was more abundant on the insular slope of the Balearic Islands. These patterns were linked to species-specific trophic strategies and reproductive traits. Adults of P. blennoides and T. scabrus (benthic feeders) were mostly found below 1000 m, associated with higher organic matter and dissolved oxygen, whereas M. moro (a benthopelagic feeder) was related to higher dissolved oxygen and fluorescence (a proxy for chlorophyll a). Juveniles of P. blennoides and M. moro were associated with high dissolved oxygen and turbidity, respectively. All three species showed ontogenetic migration, with juveniles in shallower waters (< 600 m) and larger, reproductive individuals at deeper depths (> 800 m). Reproductive hotspots for P. blennoides and T. scabrus were located on the mainland slope near submarine canyons (> 900 m), where elevated dissolved oxygen levels may enhance fertilization and egg survival. Although trawling does not reach these depths, rising deep-water temperature and salinity-possibly due to climate change-may affect the distribution and success of spawners. These findings emphasize the key role of environmental conditions in structuring deep-sea fish populations and the need for further research into anthropogenic impacts on deep marine ecosystems.
Marine ecosystems are experiencing warming events in various regions of the world. Thus, many fish species and populations are now being impacted by the warmer water temperature conditions. Previous studies have reported temperature-dependent sex determination (TSD) in various fish species. The most frequently observed TSD is masculinization at elevated water temperatures. Such water temperature impact could be a significant concern in stock assessment and fisheries management. However, few studies have demonstrated TSD in wild fish populations in the long-term. Yellow striped butterfish Labracoglossa argentiventris is an important fishery species around the Izu Islands, Japan. In the present study, we examined the impacts of ocean warming on the sex ratio (ratio of female to all) of yellow striped butterfish, based on a long-term monitoring of their sex ratio and water temperature around the Izu Islands from 1987 to 2024. The mean water temperature in the spawning season significantly increased, and the sex ratio substantially decreased after 2017. A generalized linear mixed model showed that the sex ratio was negatively related to the mean water temperature in the spawning season 2 years ago. Two-year-old fish constitute the largest proportion of the total catch. Therefore, the recent trend of higher water temperature would influence the sex ratio of yellow striped butterfish by affecting the critical period for their sex determination, skewing the sex ratio toward male dominance. The present study is a unique example of demonstrating TSD in a wild pelagic marine fish in the long term. Monitoring surveys for reproductive traits would be essential for assessing the impacts of ocean warming and improving the stock assessment and fisheries management of the fish stocks under the climate variability.
We evaluated the effects of regional environment and body size on the nutritional traits of five small pelagic species differing in habitat use, feeding behavior, and importance as prey for top predators in the California Current Large Marine Ecosystem (CCLME). Northern anchovy (Engraulis mordax), bigfin lanternfish (Symbolophorus californiensis), market squid (Doryteuthis opalescens), and boreal clubhook squid (Onychoteuthis borealijaponica) were collected in the summer of 2021 in the northern and southern CCLME. Energy density (ED), lipid, and protein content (% wet weight) were calculated for each specimen via bomb calorimetry and proximate composition analysis. Energy values from the two methods were highly correlated. Bayesian linear modeling revealed that while environmental conditions (sea surface temperature, chlorophyll-a, and upwelling) differed significantly between northern and southern CCLME, nutritional value did not vary significantly by region-an effect that was consistent across species. Body size affected both mass-specific and whole specimen nutritional value, but the direction and magnitude of the relationship varied by species. While ED and % lipid increased rapidly with size in bigfin lanternfish and moderately with size in boreal clubhook squid, it was relatively consistent across size for anchovy and market squid. Fishes were more variable in ED and % lipid than squids, while % protein was highly variable across all specimens and increased significantly with size only in boreal clubhook squid. Our results highlight the importance of assessing drivers of prey quality to predicting predator foraging and nutrient flows under climate change.
Dispersal during early life stages is a critical process shaping marine fish connectivity and population dynamics, yet direct field observations at the individual level remain elusive. This has limited our understanding of the factors controlling dispersal, including the impact of active swimming by larvae and juveniles. Here, we present a new method to reconstruct ontogenetic vertical and horizontal movements of fish on continental shelves by integrating high-resolution otolith oxygen isotope profiles, hydrodynamic models and a hidden Markov model. The shelf environment was compressed into a representative cross-section, referred to as the 'staircase chart,' where fish trajectories were inferred by matching otolith isotopes with modelled hydrographic conditions. Applying this to shelf-spawning Japanese jack mackerel Trachurus japonicus in the East China Sea revealed general ontogenetic vertical migrations and variable cross-shelf movements. Most individuals originated on the southern outer shelf influenced by the Kuroshio current, but those that showed faster growth during the first 30 days from hatch moved earlier to the inner shelf and remained south, while others stayed on the outer shelf and were advected northward. These findings demonstrate that horizontal movements, potentially reflecting active swimming, play an important role in retention and dispersal from shelf-edge spawning grounds. This newly developed framework offers a powerful tool to advance mechanistic understanding of marine fish dispersal and inform conservation and management in shelf ecosystems.
In recent decades, changes in the reproductive phenology of marine fishes in response to climate variability have become a concern for fisheries scientists. This study investigates long-term shifts in the spawning phenology of anchoveta (Engraulis ringens) using a 22-year dataset and a generalized additive model (GAM), relating spawning index with key environmental drivers of coastal upwelling (standardized upwelling index, Ekman transport and pumping, sea surface temperature (SST), and chlorophyll-a concentration) as well as biological traits such as female body condition (Kn), weight, and mean fish length. Four major findings emerged: (i) interannual and seasonal changes in fertilization levels; (ii) a transition from a single winter-spring spawning peak before 2015 to a bimodal pattern after 2015, with the appearance of a secondary summer peak; (ii) a weakening of the main winter-spring upwelling signal over time, accompanied by warmer SST and lower chlorophyll-a, whereas the summer peak coincided with stronger upwelling and cooler SST; (iii) a general decline in overall reproductive intensity despite the rise of summer spawning activity; and (iv) evidence that both spawning periods occur independently of female size, with individuals larger than 13 cm participating in both events. The GAM model explained 52% of total variability in the spawning index, with season (50%), period (before vs. after 2014) (18%), SST (28%), and the standardized Ekman Index (6%) as the most influential predictors. Overall, our results demonstrate a shift in anchovy reproductive strategies, likely driven by changes in upwelling dynamics, with potential implications for ecosystem functioning and fisheries management in the Humboldt Current system.
Global climate change is intensifying ocean deoxygenation, particularly in eastern boundary current systems such as the California Current. This study investigates the impact of hypoxic events on a nearshore, multispecies recreational groundfish fishery along the Oregon coast. Using dissolved oxygen (DO) data from the National Science Foundation's Ocean Observatories Initiative (OOI) Oregon Inshore Mooring (2018-2022, excluding 2020) and trip-level recreational fishery catch data from the Oregon Department of Fish and Wildlife, we modeled catch-per-unit-effort (CPUE) and species encounter rates as functions of DO and regulatory bag limits. Of the 709 days analyzed, 36.8% were characterized as hypoxic (DO < 61 mu mol/kg). Of the 4 years, 2021 had the most severe hypoxia and 2019 had the least. Across all trips, CPUE and average number of species encountered generally declined during hypoxic periods, indicating reduced fishing success. However, species-specific responses varied: some, such as blue/deacon and China rockfish, showed increased CPUE with higher DO levels, while others like cabezon and quillback rockfish were more frequently caught during hypoxic events. These patterns suggest that hypoxia alters species' availability and/or catchability, possibly due to shifts in fish behavior, vertical distribution, or tolerance to low DO. Notably, species with increased CPUE under hypoxia are already considered vulnerable or limiting for the Oregon recreational fishery, raising concerns about increased pressure on sensitive stocks. As hypoxic events become more frequent with climate change, incorporating DO metrics into stock assessments and fisheries management would improve population models for exploited species. Our findings highlight the need for fine-scale, species-specific approaches to recreational fisheries management in the context of changing ocean conditions and suggest that recreational fishers may face constraints in adapting to deoxygenation, especially in strongly place-based or single-species fisheries.
Fluctuations in fish populations are driven by recruitment, growth, and mortality-processes heavily influenced by environmental variability, particularly in highly dynamic marine ecosystems such as the Barents Sea. The complex, nonlinear relationships between various environmental drivers and fish stock dynamics remain challenging to capture. Building upon earlier works that predict Barents Sea cod total stock biomass using lagged hydrographic variables, we combine a wide range of updated data and machine learning techniques to improve predictions. Specifically, we employ neural networks, which excel at modeling intricate, nonlinear patterns, using hydrographic variables and fishing mortality as inputs. Our results highlight the potential of machine learning to complement conventional methods, such as linear regression models, in fisheries science, providing more accurate predictions of stock biomass in response to environmental and anthropogenic pressures.
Cephalopods are commercially valuable invertebrates with short lifespans and rapid responsiveness to climate change, making them sensitive indicators of ecosystem dynamics. In recent decades, they have become the primary target species in the East China Sea (ECS) fishery following declines in demersal fish catches. Investigating the relationship between cephalopod populations and environmental factors enables researchers to characterize the ecological conditions conducive to their proliferation. The study employed six machine learning models to predict cephalopod distributions in the coastal waters of Zhejiang. Sea water temperature (SST) and chlorophyll-a concentration (Chl-a) were identified as key seasonal distribution drivers. Family-level patterns largely reflected the dominant species, yet inter-family differences revealed distinct environmental niches: Loliginidae favored warmer, nutrient-rich waters, whereas Sepiolidae exhibited different seasonal patterns in their preferences for SST and Chl-a. Notwithstanding these general consistencies, both cephalopods exhibited distinct spatiotemporal distribution patterns under different climate change scenarios. Under RCP2.6, Loliginidae were concentrated in the coastal waters of southern Zhejiang in spring and displayed a broader distribution in autumn. In contrast, under RCP8.5, their distribution range expanded notably with a northward migration in autumn. Sepiolidae showed a more constrained spatial distribution pattern, with shifts in their concentration areas across different climate scenarios and seasonal periods. Our findings systematically establish links between cephalopod spatiotemporal distribution patterns and dynamic environmental conditions, and highlight taxon-specific responses to climate change, thereby providing a scientific reference for the formulation of future fisheries management strategies under variable climate scenarios.
