Fisheries Research最新文献

The Center for the Advancement of Population Assessment Methodology (CAPAM) was established in 2013, envisioned as an institute that could conduct, organize, and communicate stock assessment research with the aim of benefiting fisheries assessment efforts internationally. CAPAM’s activities have focused on its workshop series and consequent special issues in Fisheries Research. The information generated through CAPAM and its permanent recording as journal articles has greatly benefited the stock assessment community and can potentially contribute to modelling in general. We discuss what has made CAPAM successful, its future, and what could be done to reach the ultimate goal of producing a good practices guide for fisheries stock assessment.

Spiny dogfish (Squalus acanthias) are a ubiquitous shark species found throughout the northwest Atlantic. Understanding their abundance and distribution patterns are paramount for determining stock status and guiding harvest. Previous work describing their abundance and distribution has relied on a single fisheries independent trawl survey and focused on course size groupings, ultimately capturing only a part of their geographic distribution and making such tools unavailable for use as stock assessment inputs, respectively. Here, we develop spatiotemporal models that integrate multiple surveys’ data to provide a more holistic understanding of the species distribution over time. Models were developed to produce predictions in abundance by season (spring and fall), sex (male and female) and size (6 cm length bins) to assess differences across these dimensions. Models also incorporated environmental covariates to assess whether oceanographic conditions allow for explaining distribution patterns or addressing survey catchability concerns. Model results suggest that spiny dogfish spatiotemporal dynamics were influenced by bottom water temperature. Distributional metrics (northings, eastings, effective area occupied) were largely similar between males and females over time, but highlighted seasonal patterns that reflect their seasonal migrations. For both sexes and season, relative abundance estimates have been stable over time; however, male abundance has increased in recent years in both spring and fall. Integrating the surveys into a single index has not changed perception on spiny dogfish abundance trends for this region, but better accounts for the species’ range. Through the development of these models, we provide more holistic, model-based relative abundance indices for future use in stock assessments of northwest Atlantic spiny dogfish.

Bait quality is an important characteristic that can influence the catchability of target species and contribute to sustainable fishing practices. We used bioelectrical impedance analysis (BIA) to assess the impact of various handling treatments on the quality of sea mullet (Mugil cephalus); a commonly used bait on SMART (shark-management-alert-in-real-time) drumlines in the New South Wales (NSW, Australia) shark management program. Specifically, we focused on the consequences of reusing sea mullet as drumline bait to improve the cost-effectiveness of a program incorporating 305 drumlines and spanning ∼1200 km of the east coast of Australia. After being deployed in seawater for 10 hours at 15°C, 20°C and 25°C temperatures in a flow-through mesocosm aquarium, sea mullet underwent brining, freezing, and ice storage treatments. Electrical impedance (comprised of resistance and reactance) was used as a bait quality indicator. Brining improved bait quality by reducing impedance, ice storage indicated potential quality declines while frozen baits remained stable. Resistance and reactance values of iced fish significantly increased with increasing temperature. Freezing baits showed considerable variation among resistance and reactance values. The results indicate that sea mullet could possibly be reused as bait. However, these reuse procedures now need to be tested in field trials to assess for any changes in the catchability of target sharks relative to fresh bait. We also demonstrate the utility of BIA for rapid, non-destructive assessment of bait quality.

Understanding longline fisheries dynamics is crucial for sustainable resource management. This study aims to provide a panorama of the fishing effort of the principal nations that have exploited tuna and associated species in the Atlantic Ocean for the past decade, integrating vessel data from Global Fishing Watch (GFW) and catch data from the International Commission for the Conservation of Atlantic Tunas (ICAAT), with specific information on the production of these different fleets and resources. Twelve nations represented 94.6 % of all Apparent fishing hours (AFH) of the total effort in the Atlantic Ocean and 99.9 % of all catches in the last years. Our study revealed that regions proximate to the continental shelf break and oceanic islands exhibit notably higher fishing effort than other areas within the Atlantic Ocean. We also highlight a declining trend in fishing efforts in the last ten years, likely due to regulation and overfishing. The blue shark (Prionace glauca) was the most caught species in biomass, representing 38.1 %; bigeye tuna (Thunnus obesus) represented 20.5 %; swordfish (Xiphias gladius) 15.1 %; albacore tuna (Thunnus alalunga) 11.3 %, and yellowfin tuna (Thunnus albacares) 6.1 %. The alarming trends in pelagic shark catch emphasise the need for immediate conservation actions. Management strategies should target critical nations, addressing their significant contributions to shark catch. The lack of information on several species and periods highlights the need for comprehensive research and management initiatives.

Mugil curema is a common species in America and some African coastal areas. It is thought to perform reproductive migrations to the open sea and possibly spawn in estuarine waters. Previous studies described it as a species complex composed of cryptic species, which could be explained by reproductive isolation and/or philopatric behavior. In order to assess genetic diversity, genetic structure and philopatry in M. curema, we sequenced and analyzed two mitochondrial genes (control region and Cytochrome Oxidase Subunit I [COI]) and 10 microsatellite loci from adult individuals from 10 locations in the Gulf of Mexico, one in the Atlantic Ocean, and three in the Mexican Pacific. The mitochondrial results showed two genetic groups: Gulf of Mexico (GOM) and Mexican Pacific (MP). There was relatively high genetic distance between the groups (4.5 % for COI and 11.7 % for the control region), but they did share haplotypes. In addition, two genetic groups were found within the MP group, which could constitute cryptic lineages. The microsatellite results showed genetic connection between GOM and MP, probably as a consequence of recent contact. The results also showed genetic structure within GOM and MP; genetic subgroups differed between the sexes in the GOM (F_ST=0.348 ♂ and 0.275 ♀), but not the MP (F_ST=0.233 ♂ and 0.166 ♀). The results of genetic structure and gene flow support the hypothesis of regional philopatry in males in the GOM and both sexes in the MP. The difference between regions could be explained by the fact that these are located geographically on different oceanic slopes. We recommend that areas where there is strong mixing of males and females and high genetic diversity be considered conservation priorities.

State-space models are now a common tool for modeling time-varying ecological phenomena. This extends to state-space stock assessment models (SSAMs), recognized as pivotal components within the evolving landscape of next-generation stock assessment methodologies. Though methods are rapidly evolving, the estimation of time-varying rates of natural mortality (M) remains a challenge, and the sensitivity of stock assessments and management advice to assumed M values underscores the pressing need for improved estimation methods. Using southern Grand Bank (SGB) Atlantic cod as a case study, we introduce a novel approach to estimate time-varying M. We first convert a length-based starvation M index into an age-based index, which we then include in an age-based SSAM to estimate two components of M: starvation M and a remainder component. This produces a new SGB cod SSAM with time-varying total stock M. This model produces a large decrease (68 %) in the size of the model process errors (i.e., their standard deviation) and better fit compared to a model that did not account for time-varying M, indicating that the starvation M index improves our model of stock productivity. By leveraging readily available information on fish body condition and the proportion of fish in really poor condition, the proposed methods offer a valuable solution to the challenges associated with estimating time-varying M. The proposed methods offer a tractable solution to the common struggles associated with quantifying changes in fish productivity, which is crucial for the management of dynamic systems.

In New South Wales (NSW), Australia, the majority of the commercial catch of eastern rock lobster (Sagmariasus verreauxi) is captured from traps fished on the mid and outer continental shelf in depths 50 – 220 m (119.5 t in 2021–22: 66.5 % of landings). Hermit crabs are the greatest bycatch from this fishery. The Fishery Management Strategy (2007) for the NSW lobster fishery, recognised the need to quantify by-catch species associated with lobster catches with an emphasis on increasing knowledge of the populations of hermit crabs along the NSW coast. An observer-based survey during 2008 and 2009 quantified by-catch from the fishery including, for each hermit crab species identified: (i) spatial and temporal distribution; (ii) relative abundance (number per trap-lift), and (iii) size distribution (shield length, SL). A total of 5782 hermit crabs were collected from 70 offshore trips comprising 722 trap-lifts. No hermit crabs were collected from 73 inshore trips (< 50 m depth) comprising 3232 trap-lifts, due to the low number (seven) of hermit crabs observed. Five species of hermit crab were identified. Three species were captured in very low numbers: Dardanus crassimanus (n=2), Dardanus pedunculatus (n=2) and Dardanus australis (n=1). The striated hermit crab (Dardanus arrosor; Herbst, 1796; n = 1970) and the stridulating hermit crab (Strigopagurus strigimanus; White, 1847; n =3812) were common in all latitudinal zones (30° - 37°S) and offshore depths (50–220 m) sampled. Abundance of D. arrosor decreased southward in contrast to S. strigimanus that showed the opposite pattern. Both species were more abundant on the outer-shelf than the mid-shelf. Mean SL of males was greater than females for both species across all latitudes on both the mid- and outer-shelf. Annual catches by the commercial fishery, by latitude and depth, were estimated for each species. This research provides a baseline for monitoring and interpretation of any future changes in the distribution and abundance of hermit crab species along the NSW coast.

The installation and operation of floating offshore wind power is an integral component of societal transition to renewable energy generation where fixed bottom offshore wind is not possible. However, it will cause unique ecosystem changes. To disentangle the effects of offshore wind installations from the concurrent effects of climate change and the fishing practices on commercially significant resources, we must develop detailed characterizations of the resources before development occurs. In the Gulf of Maine, American lobster is the most commercially and culturally important fishery. At the time of writing, this is the largest fishery by value in North America. Our understanding of baseline localized parameters (such as catch per trap at the spatial scale of individual turbines) should be informed by relationships to environmental, biological, and survey-specific functional drivers of catch. A more mechanistic understanding of catch will allow for strategic adjustments to Post-Deployment fishery responses and ultimately, the development of research- and commercial-scale floating offshore wind development. Here, we used survey data from the New England Aqua Ventus Pre-Construction Commercial Trapping Survey to develop Generalized Additive Models describing seasonal catch per trap for legal and sublegal lobsters. We found fall catch to be nearly twice that of spring. Bottom temperature dynamics could be used to predict catch, and the Fall survey was associated with a warmer temperature regime. By using analytical tools that incorporate environmental heterogeneity, we developed monitoring methods from pre-construction baseline data that will be applicable over the post-construction operating period of an offshore wind farm.

The use of morphology to investigate the population structure of fishes is an increasingly used technique in fisheries science. Understanding population structure helps ensure fisheries sustainability and preserves intraspecific biodiversity, which is key to ecosystem functioning. Here, the landmark-based geometric morphometric technique was utilised for the first time on New Zealand snapper (Chrysophrys auratus), a sought-after fish in both recreational and commercial fisheries. Evidence of regional population structure was found, the most pronounced morphological differences being in the head curvature, body depth, eye size, and caudal peduncle width. There were statistically significant differences in body morphology between all but one of the hypothesised populations, with C. auratus individuals correctly allocated to the appropriate populations 86 % of the time. To test optimal population configuration for management areas, several scenarios were run where individual fish were reassigned to different groups, but there was no improvement in allocation success. However, a scenario that excluded fish near the boundaries of current management areas improved allocation success to 99 %. The morphological findings in this study align with other productivity measures for these populations, suggesting that current stocks are comprised of multiple populations. This population structure must be considered at a management level to prevent localised depletions and conserve crucial intraspecific biodiversity.