Fisheries Management and Ecology最新文献

The Delphi method was used to gather assessments from 93 experts about drivers of future angling participation by locals and tourist anglers in Denmark, Finland, Iceland, Norway, and Sweden. The main drivers of future angling participation related to habitat and fish populations, and access to and information about fishing. For Norway and Finland, the predicted future decline in local angler numbers was consistent with a life-cycle model of recreational fisheries, while the anticipated increase for the three other countries contradicted the model. For tourist anglers, growth was expected for both domestic and foreign tourists. Long-term and societal drivers, such as urbanization, sociocultural changes, and climate change were not seen as strong drivers, and may be considered out of reach by managers, but should be included with information and conservation drivers in angler recruitment and retention strategies.

The Mekong River is the most productive inland fishery in the world and identified as a valuable source of hydropower generation. Consequently, benefits of energy production must be traded off against impacts on other ecological and environmental services, especially on fisheries that have been largely downplayed. We surveyed fish markets in 12 provinces in the Lower Mekong River Basin (LMB) to quantify the diversity, abundance and prices of fish species and to account for potential impacts of water infrastructure and development projects. Of 116 species in nine major ecological guilds in markets, potamodromous main channel spawners were the most diverse guild that contributed 30% of species and were present in markets in all countries and sites, whereas anadromous species were the least diverse guild with two species in Vietnam only. More than 45% of fish recorded in local markets in Cambodia and more than 80% in Vietnam were small-sized fish (<25 cm), whereas about 50% of fish marketed in Lao PDR and Thailand were large-sized fish (>50 cm). Fish were sold by both size and species, with most species sold in only one size category. The first-sale price was highest in Lao PDR, followed by Thailand, Vietnam and Cambodia. Our findings provide primary ecological and economic information that can be used to estimate potential economic losses of fisheries when considering trade-offs between energy and the environment.

To enhance management of aquatic systems, long-term monitoring programs are crucial. However, managers often lack sufficient guidance in decision-making. In this study, we analyzed nearshore electrofishing data from Lake Ontario spanning 18 years and over 100,000 caught fish to assess sampling designs for various coastal habitats. Using simulation, we evaluated precision of catch per unit effort (CPUE) for all species, piscivores, and specialist species, at different levels of electrofishing sampling effort. For overall CPUE in any habitat type, increased precision declined with additional electrofishing runs, particularly after reaching 30–40 runs. Adjustments in sampling effort, such as adding 10 runs per year for open-coast sites, increased precision of overall CPUE by 10%. Adding 8 runs per year for wetlands increased precision of specialist-species CPUE by 10%. However, additional runs in embayments did not increase precision for all species, piscivores, or specialist species. Our findings underscore the importance of considering community composition and abundance when evaluating CPUE precision and illustrates a flexible approach to optimize sampling effort in aquatic monitoring programs.

Gear selectivity is crucial in fisheries management because it influences the size and species of fish caught, with traditional methods often basing optimal mesh size on the mature length of a target species. However, to ensure sustainable fisheries, both biological aspects of resource protection and fishing operation efficiency must be considered. This study aimed to determine the ideal mesh size for trap fishing of marbled flounder (Pseudopleuronectes yokohamae) in Gyeongsangnam-do, South Korea, by using biological and economic factors for sustainable fisheries management. We sampled fish caught in traps of varying mesh sizes (35, 50, 65, 80, and 100 mm) and developed two models based on fish maturity, bycatch ratio, and CPUE. Model 1 used a maturity criterion of 17.8 cm, and Model 2 used the legal minimum length limit of 20 cm. Net selectivity curves indicated that the optimal mesh size ranged 50–65 mm based only on a minimum mature body length of 17.8 cm. In contrast, the optimal mesh size based on both biological and economic factors ranged 57.5–90 mm. Our findings could guide policymakers in enhancing marble flounder population management strategies through policy adjustments in mesh size and gear restrictions.

Sustainability of natural stocks of crayfish is critical because of their economic and ecological importance. Crayfish (Pontastacus leptodactylus), one of the most important species in Turkish inland fisheries, has been facing serious threats recently. One threat the species faces is high landed bycatch of undersized crayfish because of selective fishing gear, such as fyke nets. We estimated size-selectivity of sorting grids with various bar spacings for crayfish to reduce bycatch. Six bar spacings (15.0, 17.5, 20.0, 22.5, 25.0, and 30.0 mm) were tested alongside commercial crayfish fyke nets. Mean selectivity (L₅₀) (±95% CI) was 6.90 (6.63–6.99) cm for 15.0 mm bar spacing, 7.52 (7.16–8.02) cm for 17.5 mm, 8.52 (8.32–8.71) cm for 20.0 mm, 9.70 (9.28–9.90) cm for 22.5, 10.75 (10.34–11.17) cm for 25.0 mm, 11.80 (11.31–12.24) cm for 30.0 mm, and 8.79 (8.05–9.29) cm for commercial fyke nets. The proportion of undersized specimens caught be reduced from 32.27% for commercial fyke nets to as low as 2.46% by using sorting grids. The codend of 22.5 mm bar spacing was more selective, with significantly lower discard rates, and more effective for individuals above the minimum conservation reference size than commercial fyke nets.

Spatial and temporal distribution of European eel (Anguilla anguilla) during 1967–2020 was used to model European eel distribution in response to climate variability. Modeling integrated predictions from two distinct models for inferences. First, modeling of the relationship between temperature and precipitation and European eel catch values using multiple time-series regression analyses showed that climate variables contributed to eel distribution in Türkiye. Eel catch became restricted to western and southern coasts of Türkiye and total catch decreased between 1967 and 2020. From 1967 to 2020, favorable climatic conditions for European eels in Türkiye were characterized by moderate temperatures. Furthermore, projections for 2050 and 2070 suggested that suitable habitat would be lost in Türkiye. Our findings underscore the urgent need for immediate and widespread implementation of effective conservation policies to mitigate threats to European eel in Türkiye and globally.

Understanding drivers of effort and catch is important for sustainable management of recreational fisheries. For the Pipi (Latona deltoides) fishery in South Australia as a case study, publicly available datasets on fisher demography, market forces and internet connectivity improved understanding of fisher motivations and capabilities, identified different historical periods in the fishery and addressed temporal gaps in effort and catch estimates from on-site surveys. Most variables were correlated with recreational effort and catch estimates from on-site surveys and principal component analysis identified 2013–2014, 2015–2018 and 2019–2022 as distinct periods in the Pipi fishery. Results corroborated studies and anecdotal information that suggested declining availability and higher prices of local, commercially caught Pipi, and reduced imports of bivalves from Asia that previously supplied the South Australian bait market. Reduced availability and higher prices of Pipi likely motivated recreational fishers to gather their own bait to increase catch over the years. Similarly, increased internet and smartphone access and increased numbers of utility vehicles aided recreational catch efficiency of Pipi. Effective management of recreationally harvested resources requires understanding of external processes that drive fisher motivations and capabilities, particularly for stocks that are shared among fisheries. The need for improved data on fisher behaviour for management of recreational fisheries can be addressed by leveraging external information from available datasets. We recommend that the temporal gap between surveys should be less than 5 years, supplemented by analysing behavioural information collected from fishers during interviews.

Lakes are important in supporting ecosystem services and livelihoods. However, their food webs and ecological functioning are continuously threatened by anthropogenic influences. Food web models have been widely used in studying trophodynamics, fisheries impacts, and ecological functioning of temperate lakes, but less often in Afrotropical lake systems. We used Ecopath mass-balanced trophic models annually in 1999, 2010, and 2020 to assess trends in ecosystem function, and the impact of fisheries on the Lake Baringo Ecosystem, a shallow freshwater lake in Kenya. Pre-balance (PREBAL) and Pedigree analyses supplemented Ecopath models. Model input data were from field sampling, published and gray literature. Food web trophic models indicated a bottom-up grazer and detrital food chains in all 3 years. Odum's ecosystem development indicators (total productivity to total biomass and total respiration ratios; TPP/TB and TPP/TR) showed that the lake was in a low to intermediate developmental stage, with room for bio-manipulation, and a highly reduced mean transfer efficiency (TE) (6.4%–0.49%) indicated low trophic transfer of internal production. System omnivory (SOI) and connectance (CI) indices that varied among years indicated temporal variation in food web complexity. Indices of system resilience (overhead and ascendency) indicated an increasing potential for the lake to recover from perturbations. The mean trophic level of the catch (MTLc) increased from 1999 to 2010 and decreased in 2020, by fishing down the food chain as fishing pressure increased. Oreochromis niloticus, an endemic cichlid, was the keystone species (KSi >0) controlling community structure, while the lungfish Protopterus aethiopicus, the top predator in the lake, was not a keystone species (KSi <0). We recommend an integrated approach to lake management that incorporates watershed regulations, regulates fishing effort on the keystone species (O. niloticus), and monitors water quality for sustainable management of the Lake Baringo ecosystem.

The addition of coarse woody habitat (CWH) is often used to mitigate the loss of natural structure in aging waterbodies. Ecosystem-scale effects of large-scale CWH additions and their influence on fish productivity have been assessed in oligotrophic, natural lakes, but need to be assessed in more ecosystems. Therefore, we tested the effects of an ecosystem-scale addition of CWH to a eutrophic reservoir using a reference reservoir and data from 4 years before and 4 years after habitat enhancement. Zooplankton and benthic macroinvertebrates did not respond to the addition of CWH, but bluegill (Lepomis macrochirus) reproductive productivity and largemouth bass (Micropterus salmoides) size structure increased. Positive fish responses that contrasted with a lack of fish population-level responses after a similar CWH addition in an oligotrophic, natural lake highlight the importance of assessing the efficacy of CWH addition across diverse ecosystems.

Composition, size distribution, structure, and function of deep-sea marine communities must be understood before they are impacted by anthropogenic effects. The deep-sea ecosystem of the Colombian Caribbean Sea is unexploited with no fishing activity ever registered. We quantified the current state of the marine community using body size distribution (size-spectra), size-based indicators, minimum length (L_MIN), maximum length (L_MAX), average length (L_mean), standard deviation of length (L_SD), 10th and 90th percentiles of the length distribution, Shannon–Wiener diversity (H′), and Pielou's evenness (J′) to generate a baseline of potential ecological indicators that contribute to management and conservation of the Colombian bento-demersal community of deep-sea marine ecosystem. Sampling was in the Colombian Caribbean Sea at 58 stations during four samplings in August and December 2009, 21 stations in March and May 2010, and 45 stations from August to December 2020, using the swept area method, at depths of 200–550 m. Catches included >50% families and species of fish, followed by 27 families (30%) and 33 and species (37%) of crustaceans. Chondrichthyes included 14% families and 9–11% species. Cephalopods included 2–3% families and 1–4% species. Size-spectra analysis confirmed expected values for unexploited communities in three sampling years for teleostei, crustacea, and whole community.