Commercial Fisheries Research Articles

Estuarine residency and habitat preferences of Atlantic Tripletail in the northwestern Gulf of Mexico

AbstractObjectiveThe Atlantic Tripletail Lobotes surinamensis is a globally distributed subtropical and tropical fish species that inhabits estuaries throughout the northern Gulf of Mexico (GOM), particularly during warm months. Little is known about distribution and residency patterns within estuaries, as the species is rarely caught in the recreational fishery, and virtually no commercial fishery exists for the species in the GOM.MethodsWe used data from a long‐term fishery‐independent gill‐net survey to model estuarine distribution throughout Texas and to relate environmental variables to the Atlantic Tripletail catch.ResultAlthough there were no observable temporal trends in catch over the time series (1990–2022), the most recent 6 years included record catch in six of the 10 major Texas estuaries, possibly indicating a recent pulse in abundance. Catch throughout the time series was spatially aggregated in a small number of “hot spots” observed coastwide. Latitude was the best predictor of catch, although wind fetch and wind aspect (wind direction in relation to shoreline direction) were important predictors, and catch was highest near GOM inlets. The Texas Parks and Wildlife Department gill‐net sampling program caught a range of Atlantic Tripletail between 171 and 880 mm total length, indicating a potential gear bias against juveniles.ConclusionDespite this gear bias, these data shed light on the factors that drive Atlantic Tripletail estuarine distribution and abundance in the northwestern GOM. Wind‐driven passive movements in the estuary, combined with active selection of polyhaline habitats near GOM inlets, might be primary drivers of Atlantic Tripletail catch, thus supporting findings from previous studies.

Analysis of natural occurring radionuclide activity concentration of fish in west coast waters of Sabah, Malaysia

Abstract Fish is an important source of protein in human diets, but concerns arise due to natural radionuclide contamination in food and water sources. The study aimed to assess the concentration radionuclides activities (232Th, 238U, and 40K) in three commercial fish species from west coast waters of Sabah, Malaysia. Additionally, the annual effective dose and cancer risk for adults consuming these fish were evaluated. The concentration analysis was conducted using the inductively coupled plasma-mass spectrometer (ICP-MS) technique. The average concentration levels of radionuclide activity detected, and the annual effective dose was estimated to be much lower than UNSCEAR recommendations. The collective effective dose was estimated at 1.88 μSv y−1 for 232Th, 1.11 μSv y−1 for 238U, and 15.12 μSv y−1 for 40K. The cancer risk for adults from the annual effective dose was also found to be much lower than UNSCEAR and ICRP recommendations. Based on the study’s findings, consuming fish from west coast waters of Sabah is deemed safe. However, it is recommended to establish a long-term monitoring system for radionuclide bioaccumulation in fish to gather valuable information for assessing the potential health risks associated with radionuclides in Malaysia, particularly in the Sabah.

Development and analyses of stakeholder driven conceptual models to support the implementation of ecosystem-based fisheries management in the U.S. Caribbean.

Fisheries management agencies in the U.S. Caribbean are currently taking steps into transitioning from a single species approach to one that includes Ecosystem Based Fisheries Management (EBFM) considerations. In this study, we developed and analyzed stakeholder-driven conceptual models with seven different stakeholder groups in Puerto Rico and the US Virgin Islands to assess and compare their perceptions of the fishery ecosystem. Conceptual models were developed for each stakeholder group during 29 separate workshops involving a total of 236 participants representing Commercial Fishers, Managers, Academics, Local Businesses, Environmental NGOs, and the Caribbean Fishery Management Council (CFMC) District Advisory Panels (DAPs) and Scientific and Statistical Committee (SSC). Non-Metric Multidimensional Scaling (nMDS) and two-mode social network analysis were used to investigate differences and similarities between stakeholder groups as well as to identify priority ecosystem elements and threats. Results show important variations between stakeholders and islands in terms of their perceived importance of ecosystem components and relationships, which supports the need for collaborative approaches and co-production of knowledge in the United States (U.S.) Caribbean region. Despite this variation, important areas of common concern among stakeholders were identified such as: habitat integrity (e.g., coral reefs), water quality, and influence of recreational fisheries and tourism on marine ecosystems. Findings of this study support the use of stakeholder-driven conceptual models as effective tools to guide decision-making, aid prioritization of data collection, and increase collaboration and cooperation among stakeholders in the context of fisheries management.

A new and widespread group of fish apicomplexan parasites

Apicomplexans are obligate intracellular parasites that have evolved from a free-living, phototrophic ancestor. They have been reported from marine environmental samples in high numbers,1 with several clades of apicomplexan-related lineages (ARLs) having been described from environmental sequencing data (16S rRNA gene metabarcoding).2 The most notable of these are the corallicolids (previously ARL-V), which possess chlorophyll-biosynthesis genes in their relic chloroplast (apicoplast) and are geographically widespread and abundant symbionts of anthozoans.3 Corallicolids are related to the Eimeriorina, a suborder of apicomplexan coccidians that include other notable members such as Toxoplasma gondii.4Ophioblennius macclurei, the redlip blenny, along with other tropical reef fishes, is known to be infected by Haemogregarina-like and Haemohormidium-like parasites5 supposedly belonging to the Adeleorina; however, phylogenetics shows that these parasites are instead related to the Eimeriorina.6,7 Hybrid genomic sequencing of apicomplexan-infected O.macclurei blood recovered the entire rRNA operon of this apicomplexan parasite along with the complete mitochondrion and apicoplast genomes. Phylogenetic analyses using this new genomic information consistently place these fish-infecting apicomplexans, hereby informally named ichthyocolids, sister to the corallicolids within Coccidia. The apicoplast genome did not contain chlorophyll biosynthesis genes, providing evidence for another independent loss of this pathway within Apicomplexa. Based on the 16S rRNA gene found in the apicoplast, this group corresponds to the previously described ARL-VI. Screening of fish microbiome studies using the plastid 16S rRNA gene shows these parasites to be geographically and taxonomically widespread in fish species across the globe with implications for commercial fisheries and oceanic food webs.

Inuit Traditional Ecological Knowledge of Anadromous Arctic Char, iqalukpik (Salvelinus alpinus) Under Changing Climatic Conditions in the Amundsen Gulf, Western Canadian Arctic

Inuit in the western Canadian Arctic have observed climate change impacts in marine and freshwater environments that have resulted in changes in the abundance, movement ecology, and health of Arctic char, iqalukpik (Salvelinus alpinus), with implications for their fisheries. This research was co-designed with Inuit to investigate reported changes in anadromous Arctic char in waters near Ulukhaktok, Northwest Territories, Canada. An analysis of semi-structured interviews with 26 Inuit fishers not only documented changes in Arctic char population abundance, spatial movement, appearance, and taste but also changes in access to the fishery. Over the past several decades and becoming pronounced in recent years, fewer fish and specifically fewer medium-sized fish that are preferred by fishers, have been caught using nets near the settlement, with some showing poor body condition, and others appearing to originate from lakes outside of the expected spatial range, earlier in an extended summer coastal fishing season. Inuit have observed changes in individual fish with broader environmental changes that are also disrupting fishing activities: the increasing prevalence of Pacific salmon, warmer air and marine sea surface temperatures, inconsistent sea and lake ice conditions, stronger and more frequent wind and wave activity, fluctuating water levels in rivers, and a seasonal tunicate bloom. Inuit have responded to these changes by altering personal subsistence fishing practices and temporarily halting a small-scale community-based commercial fishery because of observations in stock declines and in order to prioritize the subsistence fishery.

Growth–feeding linkage in small pelagic fish larvae in the Kii Channel, Japan

AbstractThe linkage between growth rate and feeding success has been shown to strengthen the effects of early growth rate on later growth rate in the early life history of fish. However, the growth–feeding linkage largely remains to be tested at the individual level within the same populations/cohorts. We examined the growth–feeding linkage for multiple populations/cohorts in Japanese anchovy Engraulis japonicus larvae and Pacific round herring Etrumeus micropus larvae, through otolith microstructure analysis, based on samples collected from the commercial fishery for larval fish in the Kii Channel, Japan. The three growth–feeding mechanisms, which are based on the respective potential advantages of larger somatic size, higher growth rate, and earlier morphological development for achieving feeding success, were tested to understand how growth rate relates to feeding success. The “somatic size” mechanism was supported for all of six samples for anchovy larvae and three of four samples for round herring larvae. The “growth rate” mechanism was supported for two of six samples for anchovy larvae and three of four samples for round herring larvae. The “morphological development” mechanism was supported for three of four samples for anchovy larvae and all of three samples for round herring larvae. Overall, the present analysis supported the growth–feeding linkage but revealed the dynamics of the growth–feeding mechanisms. All the mechanisms were shown to operate at least for certain populations/cohorts, but none of them were universally effective over all populations/cohorts across the two species. Understanding the dynamics of the growth–feeding mechanisms would provide precious hints for considering strategies of predicting recruitment dynamics.

Optimization of the stowage of fishing discards: Innovations in trawlers in the Gulf of Cadiz (SW Iberian Peninsula)

Discards in commercial fisheries are a common practice that generates negative impacts on fish resources and the environment. This study addresses the challenge of stowing discards in trawlers operating in the Gulf of Cadiz, with the aim of complying with landing regulations and ensuring the safety of fishing operations. The fleet was classified into three groups based on the length (m), power (kW), and tonnage (GT) of the vessels. Through port visits, efficient discard stowage designs were proposed. A SWOT analysis was conducted to assess discard management, leading to proposals based on decision matrices and the establishment of strategies for their management. Subsequently, stowage solutions were proposed for both new and existing vessels, with alternatives such as trays, boxes, and containers, with the optimal solution determined for each vessel type. This study highlights the complexity of discard management on vessels, considering their individual characteristics. Additionally, discard stowage alternatives based on the size and volume of catches are proposed, which could facilitate their handling. Finally, the need to implement a discard treatment system at the fish market is emphasized to achieve comprehensive management of discarded catches.

Preliminary design and hydrodynamic study of power-driven float pole system in Pacific saury fishery

Pacific saury (Cololabis saira), an essential commercial fish species in the North Pacific Ocean, is captured primarily using the stick-held dip net (SHDN) method. During the netting process, the separation of the gear from the vessel is dependent on the wind and currents, which represents a passive operational approach. In this study, we designed a prototype power-driven device for SHDN gear. The device consists of two thrusters, a remote-control system, and an energy device. It was installed on a 1/10 length segment of a float pole, hereafter referred to as the power-driven float pole (PFP) prototype. Experiments were conducted on both the single-thruster and PFP prototype to investigate the relationship between their rotational speed and thrust. SolidWorks was used to model the single-thruster and PFP prototype, and Ansys Fluent was used to solve the Reynolds-averaged Navier–Stokes equations to obtain the hydrodynamic characteristics of both the thruster and PFP prototype. A comparative analysis of the experimental and simulated hydrodynamic results showed the following: (1) the flow velocity between the blade suction surface and pressure surface tended to decrease, and the pressure tended to increase; (2) the thrust of both the single-thruster and PFP prototype increased with the thruster rotational speed according to a quadratic polynomial relationship; (3) the thrust ratio between the PFP prototype and the combined thrust of the two thrusters under the no-load condition exhibited a logarithmic relationship with the increasing rotational speed; and (4) to meet the operational requirements of the PFP prototype with a working duration exceeding 350 min and a minimum thrust of 20 N, the recommended rotational speed range for the thrusters on the PFP prototype was 1569–1970 rpm. The results of this study provide a fundamental reference for the further optimization of the PFP configurations.

Non-native fish species in the North Aegean Sea: a review of their distributions integrating unpublished fisheries data

Fisheries-dependent data and information gathered through fisheries-related scientific surveys can significantly contribute to research on the patterns and processes underlying marine biological invasions and their interactions with fisheries. This study presents an overview of the presence of non-native fish species in the North Aegean Sea, offering insights into their distributions and impact on fisheries. The findings are based on a comprehensive compilation of commercial fisheries-dependent and scientific survey data collected in Greece from 2016 to 2023, along with a systematic review of the international scientific literature. The study resulted in the documentation of the presence of 37 non-native fish species, including several recorded for the first time in the area. The results suggest that non-native fish species invasions in the North Aegean Sea are dynamic. Although most species were classified as casual, and the frequencies of occurrence as well as the quantities in commercial fisheries catches of established species are smaller than in the South Aegean Sea, species introductions and the extent of occurrence and area of occupancy of several species have been increasing since the 2000s. The significance of non-native fish species is becoming increasingly relevant to commercial fisheries in the study area. This is particularly evident in the Northeastern Aegean Sea, where catches of non-native species are on the rise, and new species with potential commercial value have emerged in recent years.

Ecosystem structure and function of the North Water Polynya

The North Water Polynya is one of the most productive Arctic regions on Earth, sustaining the world's northernmost Inuit communities for millennia. The polynya is a large and persistent region of open water surrounded by sea ice and exhibits high primary productivity, is a biodiversity hotspot, and is a key habitat and migration corridor for Arctic species. Many aspects of the ecosystem structure and the role of resident species in the North Water Polynya remain uncertain. To shed light on these, we developed the first representation of the North Water Polynya food web using the Ecopath modelling framework. Modelled trophic flows indicated that pelagic and benthic communities were primarily connected by Age 1+ Arctic cod ( Boreogadus saida), walrus ( Odobenus rosmarus), and ringed seal ( Pusa hispida). Large copepods, Age 1+ Arctic cod, and bivalves were key prey species. Overall productivity in the North Water Polynya was higher compared to Western Baffin Bay and Western Greenland, corroborating expectations of relatively high productivity within the polynya. This model provides a baseline description of the North Water Polynya ecosystem structure and function prior to future climate-driven food web changes and the emergence of large-scale commercial fisheries.

The survival, gene expression, and DNA methylation of Paralichthys olivaceus impacted by the decay of green tide and bacterial infection in both laboratory and field simulation experiments

The recurring appearance of Ulva prolifera green tides has become a pressing environmental issue, especially for marine transportation, tourism, and aquaculture in the stage of decomposition. An abundance of decaying U. prolifera leads to water acidification, hypoxia and pathogenic microorganism proliferation, threatening marine germplasm resources, particularly benthic organisms with weak escape ability. Epigenetic modification is considered to be one of the molecular mechanisms involved in the plastic adaptive response to environmental changes. However, few studies concerning the specific impact of decaying green tide on benthic animals at the epigenetic level. In this study, decomposing algal effluents of U. prolifera, sediments containing uncorrupted U. prolifera, pathogenic microorganism were considered as impact factors, to reveal the effect of decaying U. prolifera on marine economic benthic species, Paralichthys olivaceus, using both field and laboratory simulation experiments. Field simulation experiment showed higher mortality rates and serious histopathological damage than the laboratory simulation experiment. And both the decaying U. prolifera and the sediment containing U. prolifera were harmful to P. olivaceus. Genome-wide DNA methylation and transcription correlation analyses showed that the response of P. olivaceus to green tide stress and bacterial infection was mainly mediated by immune signaling pathways such as PI3K-Akt signaling pathway. DNA methylation regulates the expression of immune-related genes involved in the PI3K-Akt signaling pathway, which enables P. olivaceus to adapt to the adverse environmental stresses by resisting apoptosis. In summary, this research analyzed the potential role of P. olivaceus in decaying U. prolifera, which is of great significance for understanding the impact of decaying green tide on marine commercial fish and also provides some theoretical guidance for the proliferation and release of fish seedlings.

Foraging niche, sex-specific resource partitioning, and mercury concentrations of male Steller sea lions in Alaska

With their large size, the foraging behaviors of adult male Steller sea lions Eumetopias jubatus may have significant impacts on marine food webs and ecosystems. Limited studies from scat suggest that male and female Steller sea lions exhibit some dietary differences, and bycatch rates tend to be higher for males; however, most foraging ecology data are from adult females. Here we aimed to (1) characterize the isotopic foraging niches of adult male Steller sea lions in the Aleutian Islands and Bering Sea (n = 18), (2) assess sex-specific resource partitioning between male and female Steller sea lions (n = 18) in this region, and (3) identify male foraging strategies associated with greater total mercury concentrations ([THg]), a contaminant of concern in the region. Vibrissae collected from males bycaught in commercial fisheries from 1998-2017 were sectioned, and sequential segments were analyzed for bulk stable isotope ratios (δ15N and δ13C values) and [THg]. Individuals exhibited temporal oscillations in both δ15N and δ13C values that reflect significant summer to winter variation in foraging. Male Steller sea lions had larger isotopic niches than females, and limited overlap of isotopic niches suggests a moderate degree of sex-specific resource partitioning in this system. [THg] were positively associated with δ15N, and individuals exhibited evidence of bioaccumulation with age. These findings represent contemporary isotopic values and the first reported Hg levels for non-pup male Steller sea lions in a region where the population is considered endangered. Together, they provide a reference for assessing shifts in foraging patterns relative to future environmental fluctuations.

Some features of natural spawning and problems of artificial reproduction of the cherry salmon Oncorhynchus masou (Brevoort, 1856)

The article discusses certain aspects of the dispersal and biology of cherry salmon, Oncorhynchus masou (Brevoort, 1856). It is noted that the species is the southernmost within the Pacific Salmon family and is also the only member of the Oncorhynchus genus whose habitat is exclusively in Asia. The decline in the number of cherry salmon across their range has been highlighted, and the main underlying factors have been identified. Some features of cherry salmon spawning run in various parts of their range are examined. A long stay of spawners in fresh water before spawning with preservation of feeding behavior is noted, which makes the species an extremely compelling object of recreational and commercial fishing. Some features of natural reproduction, such as spawning timing and fertility, depending on the habitat and size of the spawners, are indicated. The issue of preserving and restoring the species population is touched upon; the most appropriate method of its implementation is the artificial reproduction of the young with subsequent release into the natural habitat. The paper highlights a number of obstacles to the implementation of such programs, such as the undeveloped technology for growing young masu salmon and the difficulty of optimizing the temperature regime at hatcheries. As one of the limitations to increasing release volumes, it is indicated that masu salmon belongs to a species that have a long freshwater period, with the young spending up to three years in the river. A large number of juvenile masu salmon in the river leads to insufficient food supply and high mortality. In order to overcome this factor, it has been proposed to conduct research aimed at stimulating the smoltification of hatchery salmon fingerlings. This measure will allow significantly increasing the number of smolt and the return rates of spawners, which can be removed without affecting the natural populations.

Real-world waste dispersion modelling for benthic integrated multi-trophic aquaculture.

In real-world situations, marine fish farms accommodate multiple fish species and cohorts within the farm, leading to diverse farm layouts influenced by cage dimensions, configurations, and intricate arrangements. These cage management practices are essential to meet production demands, however, farm-level complexities can impact model predictions of waste deposition and benthic impact near fish cages. This is of particular importance when the cages are used for integrated multi-trophic aquaculture (IMTA) with benthic feeders, where this waste not only affects environmental conditions but also provides a potential food source. The Cage Aquaculture Particulate Output and Transport (CAPOT) model incorporated multiple species, cohorts, and cage arrangements to estimate waste distribution from a commercial fish farm in the Mediterranean between October 2018 and July 2019. This spreadsheet model estimated dispersion for individual fish cages using a grid resolution of 5 m x 5 m. The study categorized discrete production periods for each fish cage every month, aligning with intermittent changes in biomass and food inputs due to different cage management practices throughout production. This approach facilitated the use of detailed input data and enhanced model representativeness by considering variations in cage biomass, food types, settling velocities, and configurations. Model outputs, represented in contour plots, indicated higher deposition directly below fish cages that varied monthly throughout fish production cycles. Deposition footprints reflected changes in cage biomass, food inputs, and farm-level practices reflecting this real-world scenario where aquaculture does not follow a production continuum. Moreover, cohort dynamics and cage movements associated with the cage management practices of the fish farm influenced the quantity and fate of wastes distributed around fish cages, revealing variability in deposition footprints. Clearly, these findings have important implications for the design of benthic IMTA systems, with species such as sea cucumber and polychaetes. Variability in waste deposition creates challenges in identifying where the benthic organisms should be placed to allow optimal uptake of waste to meet their food requirements and increase survivability. Evidently, models have an important role to play and this study emphasizes the need for representative input data to describe actual food inputs, cage biomass changes, and management practices for more representative farm-scale modelling and essentially to improve particulate waste management. To effectively mitigate benthic impacts through IMTA, models must quantify and resolve particulate waste distribution and impact around fish farms to maintain a balanced system with net removal of wastes. Resolving farm-level complexities provides vital information about the variability of food availability and quality for extractive organisms that helps improve recycling of organic wastes in integrated systems, demanding a more representative modelling approach.

DNA Barcoding Revealed a High Percentage of Mislabeling in Commercial Fish Products: The First Empirical Survey in South Texas

Seafood mislabeling is a widespread problem that have produced a growing distrust of seafood industry. In this study, we examined the prevalence of mislabeling in fish samples from regional markets in the greater Houston area and close-by coastal communities. A total of 63 fish fillet samples were purchased, labeled, and stored at -20˚C in individual packages until DNA extraction. DNA fragments of roughly 700 base pairs encoding cytochrome oxidase I (COI) were PCR-amplified from each DNA sample. With 99.6–100% nucleotide identity in the GenBank and BOLD databases, all samples were correctly identified at the species level. The scientific names identified by DNA barcoding were matched with legally acceptable market names using the US Food and Drug Administration (FDA) Seafood List. Out of the 63 samples examined, 13 samples (20.6%) were mislabeled. Moreover, 24 samples (38.1%) did not use the acceptable market names, indicating that the FDA policy is poorly implemented in seafood industry. The first DNA barcoding survey this area warranted the need of continuous monitoring and the dissemination of the regulation combined with taxonomic knowledge.

Marine protected areas and fishing community well-being: An example from statewide socioeconomic monitoring of the California MPA network

As marine protected areas (MPAs) continue to proliferate as an ocean conservation tool, it is important to understand their socioeconomic outcomes, both in the short-term following implementation and in the long-term as they become a more permanent part of the ocean landscape. This paper presents results from an effort to conduct long-term socioeconomic monitoring of commercial fishing communities in relation to California's statewide MPA network, which was fully implemented in 2012 and consists of 124 MPAs covering 16% of state waters. To assess commercial fishing community perceptions of well-being and outcomes from the MPA network, we held virtual focus groups in 18 major port-based commercial fishing communities across California with a total of 85 participants from 2020 to 2021. Focus groups had both quantitative and qualitative components, with participants rating their fishing community and engaging in discussions on topics related to their environmental, economic, and social well-being and MPA outcomes. Results revealed that perceptions of fishing community well-being varied throughout the state, but were overall low. Key areas for improvement included recruitment and retention of participants in the fishing industry, availability and maintenance of key fishing infrastructure, and access to harvestable resources. Fishing community perceptions of the management and outcomes from the MPA network were overwhelmingly low across the state with little variation. Common reasons for participant dissatisfaction included perceptions of negative ecological and livelihood outcomes from the MPAs and a perceived lack of clear MPA management goals in addition to poor communication of those goals. Overall findings highlight the value of collecting community well-being data in coordination with long-term socioeconomic MPA monitoring to understand the greater context in which MPAs are received. A well-being approach to socioeconomic MPA monitoring also broadens policy pathways that could help improve outcomes from and beyond MPAs to support overall fishing community health.

Evaluating the unexplored recreational fishing in the Turkish Black Sea: socio-economic significance and environmental impact

Marine recreational fishing, a globally popular outdoor activity, has deep cultural roots and ecological implications. This study, conducted between 2021-2022, explores marine recreational fishing practices along the Turkish Black Sea coast. It analyzes fisher numbers and demographics, fishing effort, fishing methods, and species caught and released. Furthermore, the research sheds light on the economic dimensions, emphasizing the substantial contributions of recreational fishing to local economies. Notably, responsible practices, such as catch-and-release initiatives, demonstrate anglers’ awareness of conservation efforts. Within the Turkish Black Sea region, an observed 18.5% participation rate among a population of 24.5 million implies the presence of approximately 4.5 million marine recreational fishers. Annually, this translates to nearly 30 million fishing days, accompanied by a total expenditure of 400 million Euros. However, it’s imperative to handle these figures cautiously as the timing of the screening survey during the COVID-19 pandemic may have influenced the high participation rate, introducing a potential bias. A detailed examination of a Turkish marine recreational fisher engaged in Black Sea fishing reveals an average annual catch of 16.5 kg of retained fish and 1.2 kg of released fish biomass. When extrapolated to the larger population of 4.5 million fishers, this culminates in a noteworthy landing biomass approaching 74,000 tons. The study unveils that marine recreational fishers in the Turkish Black Sea predominantly target commercially important species, resulting in a retained biomass surpassing commercial landings in 2021. This prompts concerns about potential impacts on crucial commercial fish stocks, underscoring the imperative inclusion of recreational fisheries in stock assessments. The research, providing essential insights into the intricate dynamics of recreational fishing, lays a foundation for well-informed policies and practices that concurrently promote environmental conservation and the continuation of this valued leisure activity.

Recreational fisheries selectively capture and harvest large predators

AbstractSize‐ and species‐selective harvest inevitably alters the composition of targeted populations and communities. This can potentially harm fish stocks, ecosystem functionality, and related services, as evidenced in numerous commercial fisheries. The high popularity of rod‐and‐reel recreational fishing, practiced by hundreds of millions globally, raises concerns about similar deteriorating effects. Despite its prevalence, the species and size selectivity of recreational fisheries remain largely unquantified due to a lack of combined catch data and fisheries‐independent surveys. This study addresses this gap by using standardised monitoring data and over 60,000 digital angling catch reports from 62 distinct fisheries. The findings demonstrate a pronounced selectivity in recreational fisheries, targeting top predators and large individuals. Catch‐and‐release practices reduced the overall harvest by 60% but did not substantially alter this selectivity. The strong species‐ and size‐specific selectivity mirror patterns observed in other fisheries, emphasising the importance of managing the potential adverse effects of recreational fisheries selective mortality and overfishing.

At-sea distribution of marine predators around South Georgia during austral winter, with implications for fisheries management

The sub-Antarctic island of South Georgia is surrounded by highly productive waters, supporting dense aggregations of Antarctic krill (Euphausia superba), a vital food source for globally important seabird and marine mammal populations. These waters also support a commercial fishery for Antarctic krill. Regular monitoring of key krill predator species is undertaken at South Georgia to detect any changes in the ecosystem in response to harvesting activities. This monitoring provides essential data but is focused on land-breeding animals during the austral summer, whilst the krill fishery operates exclusively in winter. Here, we report the results of at-sea surveys to investigate abundance and distribution of krill-dependent predators from winter 2010 and 2011, which represented a “poor” krill year and “good” krill year, respectively. Correspondingly in 2011 higher numbers of krill predators were observed; notably Antarctic fur seals (Arctocephalus gazella) across the northern shelf. Spatial overlap between fur seals and the krill fishery occurred mainly within the krill fishery hotspot to the north-east, highlighting the potential for locally high levels of competition. Cetaceans were observed during both survey years, but in low numbers compared to recent studies. Gentoo penguins (Pygoscelis papua) were the most frequently observed penguin species, showing an inshore distribution and almost no overlap with the krill fishery. Diving-petrels (Pelecanoides spp.) were the most abundant flying seabirds, observed across all transects, with particularly high densities to the south in early winter 2010. In conclusion, this survey provides valuable baseline data on the distribution of South Georgia’s predators during the winter months.

Vertebral chemistry distinguishes regional populations of Blacktip Sharks in the northern Gulf of Mexico

AbstractObjectiveUnderstanding the spatial connectivity of elasmobranch populations is critical for regional fisheries management. The Blacktip Shark Carcharhinus limbatus is abundant in coastal waters of the Gulf of Mexico (GoM) and important in recreational and commercial fisheries. Based on genetic and tagging studies, GoM Blacktip Sharks are currently managed under separate quotas between the eastern and western GoM (divided at 88°W), but no studies have used vertebral chemistry to assess the population structure of adult Blacktip Sharks.MethodsWe compared vertebral elemental signatures (barium [Ba], magnesium [Mg], manganese [Mn], strontium [Sr], and zinc [Zn]) for the first year of life with last occupied habitats (vertebral edges) in Blacktip Sharks collected from the western (Texas and Louisiana) and eastern (Alabama and Florida) coastal waters of the northern GoM.ResultWe found significant regional differences in Ba, Mg, Mn, and Sr vertebral edge signatures, suggesting ecological separation of Blacktip Sharks. Significant correlation between first‐year and edge signatures suggested a high degree of residency between life stages. Cross‐validated discriminant function analyses yielded highest regional classification accuracies when Florida sharks were grouped separately west of 88°W (90%), demonstrating the unique elemental signatures of eastern versus western GoM Blacktip Sharks under current management delineations.ConclusionCombined, these findings demonstrate that trace element markers can distinguish regional populations of Blacktip Sharks and provide a complimentary approach in addition to genetics and physical tagging to support current stock management efforts.