Fisheries Management and Ecology最新文献

We used the bycatch of Caspian sturgeon to quantify the species composition, length structure, spatial and temporal distribution, temporal dynamics of relative abundance (indexed as catch-per-unit-effort, CPUE), effects of fingerlings released, and to forecast future sturgeon stock status. Dynamic factor analysis of temporal changes in species CPUE was used to quantify relationships to environmental variables (sea surface temperature, chlorophyll-a, sea surface level, and river discharge) during 2006–2022. We found that the Guilan subarea had the lowest relative abundance and differed from all other subareas. Fish abundance was highest in October and November, particularly in Mazandaran and Golestan coastal waters. Relative fish abundance declined significantly over time. Acipenser persicus was the most abundant species, followed by Aciperser gueldenstaedtii, Aciperser stellatus, Aciperser nudiventris, and Huso huso. The annual number of fingerlings released decreased during 2000–2021. Over the years, environmental variables such as sea surface level, sea surface temperature, and chlorophyll-a showed different trends, with sea surface temperature generally increasing, chlorophyll-a generally decreasing, sea surface level decreasing nearly linearly, and river discharge varying erratically without a trend in the southern Caspian Sea during 2006–2022. The relative abundance of all species decreased and was significantly related to sea surface level. Fish abundance was forecasted to decline by 2025, as sea surface temperature increases and sea surface level decreases. Illegal, unreported, and unregulated (IUU) harvest of sturgeon must be effectively regulated to ensure the survival and recovery of sturgeon populations in the Caspian Sea.

Evaluating trends in fisheries, especially data-limited small-scale fisheries, is challenging. We used fish landings to evaluate changes in composition of fish landings in rivers of the Central Amazon, from a discontinuous historical 28-year series of landings from different data collection systems in main ports of the city of Manaus, the largest consumer market in the region. Annual mean trophic level (MTL), fishing-in-balance index (FiB), and mean landed size (MSL) were estimated. MTL did not decline, FiB was positive in most years, and MSL declined. Relative catches of certain fish species were replaced by others at a similar trophic level, but mean body size declined over time. We conclude that fishing in the Central Amazon is not sustainable and would benefit from better management strategies.

Movements of common fish species in large lakes that are inadequately known is challenging for fisheries management. Pikeperch (Sander lucioperca) (n = 478; mean length = 42.1 cm; SD = 7.0), bream (Abramis brama) (n = 775; mean length = 31.1 cm; SD = 5.3) and roach (Rutilus rutilus) (n = 939; mean length = 21.4 cm; SD = 2.0) were marked with individual T-anchor tags to investigate movements in Lake Vesijärvi, a large lake situated in southern Finland consisting of several basins and managing by multiple entities. All species moved between basins, but only rarely moved outside tagging areas. The recapture rate of pikeperch was higher than roach and bream. Tagged fish consistently crossed municipality borders and water ownership units, thereby forming shared stocks, which underlined the importance of cooperation in lake restoration and a need to unite fragmented water ownership. Management of fisheries for cyprinid fishes could be more efficient if fishing targeted the most suitable areas without considering restrictions due to fragmented water ownership. Tagging data provided information on which parts of a large lake should be subjected to uniform pikeperch fisheries management. The importance of other species catch varied between different parts of the lake, thereby requiring different fishing regulations. Tagging data on common fish species provided valuable information on fish movements to support spatially explicit fisheries management.

Coastal rocky fish species support important fishing activities, but basic information is lacking for many before catches decline. Monitoring and management of coastal rocky fish species is urgently needed in Chile, but knowledge of these species is fragmentary at best. Performance of Baited Remote Underwater Video Stations (BRUVS) for assessing rocky fish assemblages was evaluated in south-central Chile. Seven medium- to large-sized exploited species dominated fish assemblages in the survey area, including five small cryptic rocky reef fishes, one agnathan and a catshark species. These seven species represented 78% of the species targeted by commercial fishing in the survey area. Furthermore, this tool provided new information on behaviour of rocky fish species. The simple, inexpensive and light nature of single-camera BRUVS may be crucial for maintaining monitoring programs along remote areas of Chile.

The cover image is based on the Note Stocking fish in inland waters: Opportunities and risks for sustainable food systems by Ian G. Cowx et al., https://doi.org/10.1111/fme.12656. Image Credit: Ian G. Cowx.

Artisanal small-scale fisheries are crucial for subsistence and food security, especially in developing countries. However, artisanal fishers face stressors, such as economic and social marginalization, conflicts, and overfishing. Socio-economic attributes potentially influence their risk perception. We investigated risk perception among artisanal fishers in a Marine Protected Area through interviews and semi-structured questionnaires. Risk perception was positively influenced by fishing environment and negatively influenced by a lack of religious beliefs. Offshore fishers faced more operating conditions and time at sea, with higher risk of losses, and perceived more health and conflict risks. Inshore fishers have higher perception of environmental degradation. Prioritizing different risk perceptions is essential for effective fisheries management. Separate management plans for offshore and inshore fisheries are recommended due to varying catch, environmental perception, socio-environmental risks, and exploited resource characteristics among artisanal fisher groups.

Effective management of migrating fish stocks requires an understanding of population structure and each stock's contribution to the fishery. Water bodies spanning across national borders pose a particular challenge. We investigated the genetic structure of 13 adfluvial brown trout populations from natal rivers and conducted a genetic mixed-stock analysis of brown trout from the cross-border Lake Pyaozero Basin in eastern Fennoscandia, using 16 microsatellite loci. Our analysis revealed a clear genetic structure of three distinct geographic groups, consisting of river-specific populations. The Western and Southern groups, which included 11 rivers, contributed over 90% to the mixed stock in the lacustrine rearing area. This mixed stock of several river-specific subpopulations renders poorly managed fishing in the area a significant threat to the entire native adfluvial brown trout population complex.

Spawning potential ratio (SPR) is an important index used by fisheries biologists and managers to determine how a fishery should be harvested to prevent recruitment overfishing. In the southeastern Caspian Sea, Iran, 3430 common carp Cyprinus carpio were caught by beach seine in 2-week intervals of two fishing seasons in 2019 and 2020. Fork length (FL) was measured to the nearest 1 cm. The age and maturity stage of 434 specimens, including 236 females and 198 males, were estimated by scale and gonad microscopic examinations. Estimated L_∞ was 71.9 and K (growth constant) was 0.09. Instantaneous total mortality (Z) was 1.08, natural mortality (M) was 0.18, and fishing mortality (F) was 0.9. Estimated SPR at current fishing mortality (0.18) was lower than the reference point (0.4). Our findings indicated that fishing mortality should be reduced to F = 0.38 for C. carpio to meet the SPR reference point of 0.4. Further, higher minimum length limits should be set to reduce fishing mortality, and catch quotas for fishing cooperative corporations should be considered to meet the 40% SPR threshold.

A formerly unexploited stock of red porgy that was intensely fished along southern Brazil in the 1970s collapsed in less than a decade. Subsequently, population dynamics or stock status has not been reported, so we updated growth parameters by analysis of otolith annual-increments and micro-increments. Growth did not change after the stock collapsed, which suggested no density-dependent effect. Given the lack of growth changes and data-limitation, we used an age-structured assessment model set until 1984 to forecast relative spawning biomass and assess recovery possibilities. Projections showed that a 19 years moratorium would have been necessary for the stock to rebuild. The model suggested an annual catch of at least 170 t in the post-collapse period because the stock did not recover, and a small-scale hand-line fishery with unreported landings continued fishing. Our results reinforced the need for more curated and up-to-date data collection to properly assess and manage this formerly abundant stock.