Fisheries Management and Ecology最新文献

The blackspotted croaker (Protonibea diacanthus) is among the highest-valued commercial marine fish species in Bangladesh. Therefore, we assessed the stock status, economic significance, and market status of blackspotted croaker in the Bay of Bengal, Bangladesh. We estimated life history parameters and sustainability indicators to determine if the stock was being sustainably managed. Size of blackspotted croaker was significantly differ temporally. Blackspotted croaker increased in weight allometrically in relation to length. Length-age life history parameters were L_∞ = 161.16 cm, k = 0.39 year⁻¹. Natural mortality M was 0.39 year⁻¹ and fishing mortality F was 0.35 year⁻¹. Catch composition and sustainably indicators revealed that the stock was prone to recruitment and growth overfishing. Medium to large sized blackspotted croaker (> 85 cm) fetched the highest price in commercial markets for the swim bladders that was worth many times more than the value of fillets. The highest demand of swim bladders in export commerce termed this species as marine gold to the fishers. Therefore, fishers were increasingly motivated to target the species. Ununiformed landing of blackspotted croaker, for domestic and international trade of swim bladder of blackspotted croaker, and poorly documented trading supply chains make this fishing industry luck-driven. Management interventions are needed to sustain the fishery and economic value.

Crustacean fisheries have increased worldwide, leading to changes in fishing practices. In San Matias Gulf, Argentina, the Patagonian red shrimp replaced Argentine hake as the main target since 2012. We analyzed this shift from 2004 to 2020 using vessel monitoring systems and landings. Fishing positions were identified using the speed rule. Gravitational centers of fishing intensity were used to assess seasonal spatial changes of the fleet, and bottom-trawling footprint was used to quantify the area of the seabed affected. Landings were pooled monthly to assess multivariate changes in landing composition. Previously concentrated around a frontal system, the fleet moved northward between 2014 and 2020, while reducing hake landings but increasing shrimp landings. The total area trawled did not change significantly, but the footprint nearly doubled. Our results can be used for fishery management by increasing understanding of spatial and temporal changes in fishing strategies for policymakers.

Anthropogenic impacts to estuaries are increasing globally, and often exceed the capacity of resource managers to effectively quantify environmental changes, design and implement effective restoration programs, or assess ecosystem response to specific restoration projects. We interviewed recreational fishers to document spatiotemporal fishing effort over a 40-year period, analyzed commercial fishing landings, to qualitatively compare the data to seagrass monitoring estimates of aerial coverage and percent cover over a four-decade period for the Indian River Lagoon, Florida (USA). Fisher effort and landings mirrored declines in seagrass percent cover, which preceded declines in seagrass aerial coverage resulting from large-scale, harmful algal blooms. A super-bloom was posited as the point of ecological collapse of the Indian River Lagoon. We recommend engaging stakeholders and incorporating local ecological knowledge into resource management programs to monitor and improve restoration outcomes by expanding the knowledge base from which decisions are made.

Elasmobranch (rays and sharks) populations are vulnerable to overexploitation due to their slow growth, late maturity, and low fecundity. Industrial fishery impacts on sharks and rays are known, whereas impacts of artisanal fisheries are less understood. We quantified catches of sharks and rays in artisanal fisheries at the Parc National du Banc d'Arguin (Banc d'Arguin), Mauritania (West Africa) during 1998–2020, a period when fishing effort increased around 2006, catches increased, but catch-per-unit-effort declined substantially. Shark nets and meagre fixed gill nets were used to catch elasmobranchs, with catches comprising over 60% of elasmobranch species. Therefore, elasmobranchs were not bycatch, but rather, the target of fisheries. Of 33 elasmobranch species captured, 94% of shark species and 76% of ray species are threatened with extinction. We recommend that management approaches should focus on fishing locations with the highest occurrence of threatened elasmobranch species in catches, through new regulations on fishing gear types and discouragement of trade in elasmobranch products from Banc d'Arguin.

Recreational fishing is a popular activity that has many social and economic benefits. Monitoring has traditionally centred around measuring fishing effort and catch. However, contemporary measures, such as fisher demographics and behaviours, which may be linked to social and economic objectives, are now recognised as necessary to meet expectations that all aspects of resource use are considered for fisheries management. The challenge for recreational fisheries is how to regularly provide information across a growing diversity of metrics, and at a scale relevant to specific fisheries, with limited resources. The Blue Swimmer Crab (Portunus armatus) is one of the most commonly recreationally harvested species in Western Australia. This species served as a case study to explore if data from five broad-scale phone-diary surveys between 2011–2012 and 2020–2021 could be adapted to meet expanded information needs. Twelve discrete fisheries represented small spatial-scale areas for fisheries management, with some variation in management arrangements (i.e., bag limits). Robust estimates of traditional and contemporary measures could be produced for three fisheries: Peel-Harvey Estuary, Swan-Canning Estuary and Geographe Bay. Traditional measures of participation, fishing effort, total catch and harvest from 2011–2012 to 2020–2021 were generally consistent for Swan-Canning Estuary but decreased for Peel-Harvey Estuary and Geographe Bay. The proportion of harvest from recreational and commercial fishing varied from mixed use (Swan-Canning Estuary, Peel-Harvey Estuary) to recreational only (Geographe Bay). Variation in contemporary measures was also evident, with recreational fishing largely undertaken by local residents in Swan-Canning Estuary, while participation was more uniform between local and non-local residents in Peel-Harvey Estuary and Geographe Bay. We found that broad-scale surveys could be successfully adapted to meet the growing need for information on contemporary measures to support a holistic approach to sustainable fisheries management for small spatial-scale recreational fisheries.

Species with high connectivity usually lack genetic differentiation. We tested for the presence of multiple populations of jumbo squid (Dosidicus gigas) on the Southeastern Pacific Ocean. Samples were collected from Ecuador to southern Chile (1.5° S–38° S). Two mitochondrial genes were sequenced (COI and ND2). Jumbo squids from all sampled locations in Ecuador, Peru, and Chile, as a whole, were characterized by low genetic diversity and an absence of spatial genetic structure, which suggest the presence of a population genetic unit in the Southeastern Pacific Ocean. Absence of spatial genetic structure was associated with high vagility of adults, eggs, and paralarvae of jumbo squid. We conclude that jumbo squid should be managed as a single biological stock along the Southeastern Pacific Ocean.

Counting departing smolts and returning adults in index rivers is essential to estimate marine survival and track population trends of Atlantic salmon (Salmo salar). However, mortalities between counting facilities and a river mouth can skew survival estimates. We used acoustic and radio telemetry to investigate survival, mortality sources and behaviour of wild salmon smolts in the River Erriff, Ireland's index river, and Killary Fjord. Smolts were tagged with acoustic tags in 2017 (n = 40) and 2018 (n = 35) and radio tags in 2018 (n = 30). Survival was low for acoustic-tagged smolts in 2017 (26%) and 2018 (47%), mainly due to riverine mortality. Terrestrial or avian predators consumed 65% of acoustic-tagged smolts in 2017 and 67% of radio-tagged smolts in 2018. Nocturnal migration and ebb tide transportation likely contributed to high estuary survival. High predation on smolts emphasised the importance of assessing freshwater mortality for effective salmon management.

Over 60% of the world's fish stocks suffer from limited data, which hampers effective fisheries management. Researchers have developed stock assessment methods for data-limited fisheries using length-frequency data, but reliability was questionable and not well researched. We evaluated the precision of the widely used length-based method ELEFAN using 24 months of length-frequency data from 14,190 individual yellowfin tuna and sequential and interval data fractions. Using bootstrapping (1000 times) and data reduction, growth parameters and precision $��L_{\infty }�$, $��K�$, and Φ′ were estimated. The CVs of $��L_{\infty }�$, $��K�$, and Φ′ were 2.55%, 23.04%, and 2.35%, respectively. From the result of data reduction, at least once in 1 or 2 months and 12 times measurements with 500 data per measurement on average is recommended for achieving high precision with CV of Φ′ < 3%.

The Bighead Catfish (Clarias macrocephalus) plays crucial roles in the ecosystem and as a protein source for humans in Nong Han Lake, Thailand, but their ecological and population dynamics, along with their genetic diversity and structure, are poorly understood. Therefore, the dynamics of genetic diversity and differentiation of bighead catfish populations in Nong Han Lake were investigated during 2018–2023 to provide essential insights into preserving biodiversity and maintaining ecological balance. Microsatellite genotyping was used to assess the genetic diversity of one bighead catfish population in 2018, two populations in 2023, and one hatchery population. Potentially stable, effective population sizes and distinct genetic clusters of these populations were identified, which represented the resilience of populations and the complexity of their genetic dynamics. Genetic differentiation between sample dates and among populations suggested that limited recent and historical genetic exchanges could potentially influence genetic structure. The impact of ecological factors, including flooding, metapopulation dynamics, and human interventions, was indicated by unique and shared gene pools among populations and subpopulations in different years. Ongoing assessment of genetic diversity and structure of bighead populations is essential for developing conservation strategies and ensuring sustainable management.