Fisheries Oceanography最新文献

The East Asian common octopus Octopus sinensis is distributed in the coastal waters of East Asia and can grow to around 2 kg in 12–18 months. This species is semelparous, and its spawning season is highly variable and depends on the water temperature, which has increased in the Seto Inland Sea, western Japan. To investigate the impact of this temperature increase on the reproductive characteristics of O. sinensis, we collected 3387 and 757 samples using small trawls in 1999–2001 and in 2019–2021, respectively, and compared the body condition of all samples and the occurrence of final maturation stage females between the two sampling periods. Paralarval abundance was also compared using samples collected with a plankton net. The relative condition factor indicated that individuals were in a worse growth condition in 2019–2021. The mean mantle length of final maturation stage females was significantly larger in 2019–2021; however, there was no significant difference in body weight between the sampling periods. Seasonal changes in the gonadosomatic index of females and the occurrence of final maturation stage females between the sampling periods indicate that the proportion of final maturation stage females peaked in September during 1999–2001 but shifted to spring and late autumn in 2019–2021. Paralarval densities in October were more than 10 times higher in 1999–2001 than in 2019–2021, which may be related to the body condition and changes in the spawning season due to increasing water temperatures.

The East Asian common octopus Octopus sinensis is distributed in the coastal waters of East Asia and can grow to around 2 kg in 12–18 months. This species is semelparous, and its spawning season is highly variable and depends on the water temperature, which has increased in the Seto Inland Sea, western Japan. To investigate the impact of this temperature increase on the reproductive characteristics of O. sinensis, we collected 3387 and 757 samples using small trawls in 1999–2001 and in 2019–2021, respectively, and compared the body condition of all samples and the occurrence of final maturation stage females between the two sampling periods. Paralarval abundance was also compared using samples collected with a plankton net. The relative condition factor indicated that individuals were in a worse growth condition in 2019–2021. The mean mantle length of final maturation stage females was significantly larger in 2019–2021; however, there was no significant difference in body weight between the sampling periods. Seasonal changes in the gonadosomatic index of females and the occurrence of final maturation stage females between the sampling periods indicate that the proportion of final maturation stage females peaked in September during 1999–2001 but shifted to spring and late autumn in 2019–2021. Paralarval densities in October were more than 10 times higher in 1999–2001 than in 2019–2021, which may be related to the body condition and changes in the spawning season due to increasing water temperatures.

Spatial models that identify statistical relationships between environmental conditions and species distributional data are commonly used in fisheries research to evaluate habitat suitability and predict distributional shifts, such as those driven by changing ocean temperature and oxygen levels. However, a lack of environmental data—particularly dissolved oxygen—at the same temporal and spatial resolution as biological data can limit these analyses. We evaluate the ability to predict bottom dissolved oxygen via imputation and extrapolation and with biophysical oceanographic models in the northeastern Pacific Ocean (Aleutian Islands, Eastern Bering Sea, Gulf of Alaska, British Columbia, and California Current). Specifically, we measure predictive skill compared to in situ observations (measured concurrently with bottom trawl data) for (1) predictions from an empirical statistical model fit to integrated dissolved oxygen observations and (2) a commonly used dynamical oceanographic model estimate of oxygen, the Global Oceanographic Biogeochemistry Hindcast (GOBH). Lastly, we evaluate how estimation and interpretation of a species distribution model are impacted by the use of different oxygen data sources. For year-out cross-validation, we find that the empirical statistical model predicts bottom dissolved oxygen for fish catch sampling events with relatively high accuracy in only certain regions (California Current and British Columbia) (root mean squared error [RMSE] ~ 16–30 μmol kg⁻¹). Prediction skill was more than two times lower in Alaska regions that did not have extensive data (around < 0.075 observations per square kilometer), and this approach would likely not provide sufficiently accurate oxygen values for SDMs in these regions. The Copernicus Global Oceanographic Biogeochemistry Hindcast had a substantially lower prediction skill than the integrated statistical predictions (RMSE ~30–90 μmol kg⁻¹). When applied to species distribution models, the estimated dissolved oxygen thresholds differed by 20–50 μmol kg⁻¹ when fit to different dissolved oxygen data sources. We focus on oxygen in the northeastern Pacific, yet our approach is generalizable to other variables and systems. We recommend increased attention to validating oceanographic models when operationalized to fisheries applications and evaluating the robustness of conclusions to environmental covariate data sources.

We developed a particle tracking model for the transport and dispersion of American lobster (Homarus americanus) larvae for the Gulf of Maine (GoM) that considers both passively drifting larval stages and their swimming ability during the postlarval (pre-settlement) stage. The model takes into account two characteristics of the postlarval stage: directional swimming toward shallower regions and diel fluctuations of their swimming speed. Diffusivity (lateral mixing), based on surface GPS drifter observations, was also considered and used to validate this model. Numerical experiments, using the hydrodynamics predicted by the Gulf of Maine Operational Forecasting System (GoMOFS) model, were conducted to test the potential impact of postlarval swimming ability on successful settlement on suitable habitat (defined as regions shallower than 20 m). The results of this experiment showed that elevated swimming ability (18 cm/s) in postlarvae significantly improves settlement success compared to trials modeling postlarvae with a diminished swimming ability (7 cm/s), or no swimming ability (control) at all. In contrast, diel swimming behavior in postlarvae slightly decreased successful settlement. In addition, ocean drifter observations and numerical simulations consistently revealed that successful settlement decreases the further the initial release point of larvae is from the coast. Combined, these experiments indicate that both the swimming ability of postlarvae and the distance they are from shore when they hatch are critical factors that influence their potential to reach viable settlement locations in the GoM. These data also suggest that if the GoM continues to warm, and females move further offshore to avoid warmer inshore waters, the settlement success of their larvae may be compromised.

We developed a particle tracking model for the transport and dispersion of American lobster (Homarus americanus) larvae for the Gulf of Maine (GoM) that considers both passively drifting larval stages and their swimming ability during the postlarval (pre-settlement) stage. The model takes into account two characteristics of the postlarval stage: directional swimming toward shallower regions and diel fluctuations of their swimming speed. Diffusivity (lateral mixing), based on surface GPS drifter observations, was also considered and used to validate this model. Numerical experiments, using the hydrodynamics predicted by the Gulf of Maine Operational Forecasting System (GoMOFS) model, were conducted to test the potential impact of postlarval swimming ability on successful settlement on suitable habitat (defined as regions shallower than 20 m). The results of this experiment showed that elevated swimming ability (18 cm/s) in postlarvae significantly improves settlement success compared to trials modeling postlarvae with a diminished swimming ability (7 cm/s), or no swimming ability (control) at all. In contrast, diel swimming behavior in postlarvae slightly decreased successful settlement. In addition, ocean drifter observations and numerical simulations consistently revealed that successful settlement decreases the further the initial release point of larvae is from the coast. Combined, these experiments indicate that both the swimming ability of postlarvae and the distance they are from shore when they hatch are critical factors that influence their potential to reach viable settlement locations in the GoM. These data also suggest that if the GoM continues to warm, and females move further offshore to avoid warmer inshore waters, the settlement success of their larvae may be compromised.

Tropical Atlantic Ocean is a vital region for longline fisheries, characterized by oceanographic features that enhance fishing productivity. However, there is a lack of information about key fishing hotspots and the factors influencing these areas, limiting efforts to optimize exploitation while ensuring sustainability. To address this gap, we analyzed monthly fishing effort data from the Global Fishing Watch platform (2019–2023) between 23.5°N and 23.5°S, focusing on the six most significant fleet nations. Spatial–temporal variables, along with fishing effort, were analyzed at a high resolution (0.01°). Distance from the nearest coastline was also calculated to assess fleet operations relative to Exclusive Economic Zone (EEZ) boundaries. To assess spatiotemporal variations and the influence of environmental variables on fishing effort distribution, we applied Generalized Additive Models. Results indicate that distant-water and foreign fleets predominantly operate outside EEZs but approach national waters between May and September. In contrast, fleets from Brazil and Venezuela mainly operate within their EEZs, likely due to operational constraints and productive fishing grounds. Our model selection process identified sea surface salinity, sea surface height, and primary production as having a positive effect on fishing effort, while sea surface temperature, longitude, and distance from the coast showed a negative effect. These findings suggest that longline fleets favor upwelling zones, as well as warm-core eddies, areas with positive SSH and high SSS, likely due to their role in aggregating target species. These insights can aid policymakers and stakeholders in identifying productive fishing areas and optimizing longline operations in Tropical Atlantic.

Tropical Atlantic Ocean is a vital region for longline fisheries, characterized by oceanographic features that enhance fishing productivity. However, there is a lack of information about key fishing hotspots and the factors influencing these areas, limiting efforts to optimize exploitation while ensuring sustainability. To address this gap, we analyzed monthly fishing effort data from the Global Fishing Watch platform (2019–2023) between 23.5°N and 23.5°S, focusing on the six most significant fleet nations. Spatial–temporal variables, along with fishing effort, were analyzed at a high resolution (0.01°). Distance from the nearest coastline was also calculated to assess fleet operations relative to Exclusive Economic Zone (EEZ) boundaries. To assess spatiotemporal variations and the influence of environmental variables on fishing effort distribution, we applied Generalized Additive Models. Results indicate that distant-water and foreign fleets predominantly operate outside EEZs but approach national waters between May and September. In contrast, fleets from Brazil and Venezuela mainly operate within their EEZs, likely due to operational constraints and productive fishing grounds. Our model selection process identified sea surface salinity, sea surface height, and primary production as having a positive effect on fishing effort, while sea surface temperature, longitude, and distance from the coast showed a negative effect. These findings suggest that longline fleets favor upwelling zones, as well as warm-core eddies, areas with positive SSH and high SSS, likely due to their role in aggregating target species. These insights can aid policymakers and stakeholders in identifying productive fishing areas and optimizing longline operations in Tropical Atlantic.