Fisheries Management and Ecology最新文献

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.

This study aimed to provide data for fisheries management of two threatened guitarfish species, by using linear and geometric morphometric analyses. Linear morphometrics (LM) has limitations in determining minimum catch sizes, whereas geometric morphometrics offers a robust approach to quantifying body form variations with the potential to influence metrics set by legislation. Based on LM analysis, Pseudobatos horkelii were larger than Pseudobatos percellens. Based on geometric morphometric analysis body form differed between the two species, particularly in the head, disk, and posterior region. P. percellens were also sexual dimorphic in body form. Our findings provide valuable insights into permissible catch size limits of these threatened guitarfish and also contribute to improvement of fisheries management strategies where catch is still allowed. The study underscores the necessity of species-specific and sex-specific management directives to effectively ensure the population recovery of both guitarfish species.

Oceans are increasingly warming through climate change. Fish and invertebrate ectotherms respond to ocean warming through poleward and depth-related migrations, a consequence of which is disruption of fisheries catch compositions. Mean temperature of the catch (MTC) is an index of change in catch composition, from colder to warmer water species. MTC is widely applied as an easily parameterised variable using readily available data (catch and species preferred temperature), but few studies underscore situations that might mask the “true” MTC trend. Here, we use fisheries catch in the Arabian-Persian Gulf (“Gulf”) to highlight, for the first time, how abrupt changes in market demand can strongly influence catch composition and thereby mask a trend in MTC, and discuss the implications of the unmasked MTC trend to fisheries in the region. We found that a recent sharp decline in MTC from 27 to 26°C, despite a gradual increase in sea surface temperature, coincided with an escalated demand for the largehead hairtail (Trichiurus lepturus), a relatively cold-water species in the Gulf, that caused catch to dramatically increase for export to overseas markets. Our findings suggest that the change in MTC reflected a fishery response to satisfy increased international market demand, rather than reflecting warming-driven changes in catch composition. When excluding the effect of T. lepturus catch, the Gulf MTC trend was stable over time and consistent with a trend in many tropical and subtropical waters. Our findings highlight that an MTC change can be masked by factors unrelated to warming-driven changes in catch composition, and that catch-only MTC trends should be examined cautiously.

Small-scale fisheries are vital to millions of rural people, but surprisingly little is known about the environmental and socio-economic factors that guide rural peoples' decisions to adopt a fishery-oriented livelihood. We analyzed data from a large-scale household survey of 3929 households in 235 rural communities in the Peruvian Amazon to develop multi-scalar quantitative models to explain engagement in fishing and the relationship between fishing livelihoods and poverty. Households harvested an average of 1000 kg of fish and sold 450 kg over the 12 months preceding interviews. The mean total annual income was 3119 USD per household and fishing contributed 27% to total income. Access to extensive floodplain habitat, geographical isolation, and an available workforce were important drivers of fishing activity, while poor market connectivity and limited financial capital restricted households from increasing the scale of market-oriented fishing. Wealthier households generally harvested more fish, whereas reliance on fisheries was greatest among poorer households who harvested less fish. Fisheries management and conservation initiatives in developing regions must consider the distinct drivers of fishing specialization across the full wealth spectrum with particular attention to “high reliance-high harvest” households.

Reduced food availability increases the capture of several fish species, although the mechanisms responsible for how food resources result in increased capture are undefined. Our objective was to quantify the mechanism by which food availability might influence the angling vulnerability of muskellunge (Esox masquinongy). We assessed capture rates in the field under different food levels, quantified the behaviors of muskellunge that were either fed or food deprived, and determined if appetite-related hormones leptin and ghrelin affected fish behavior. Catch rates of fasted muskellunge were more than twice as high as those of fed muskellunge. However, food deprivation and hormonal treatments did not influence laboratory behavior, which suggested that catch rates of food-deprived muskellunge increased because fish were more receptive to lures. Furthermore, an ecosystem approach should be used to consider forage as a component of management goals.

An understanding of egg densities and juvenile production is critical in salmonid egg stocking projects, but the question is not deeply studied. Given that managers rely on the number of young of the year (YOY) fish to evaluate stocking success, this knowledge gap poses a major challenge. We studied effects of two stocking levels on YOY brown trout at different downstream distances (0–600 m) from the stocking point. Density increased significantly with increasing distance from the stocking point when 60,000 eggs were stocked but not when 30,000 eggs were stocked. Body length was not related to distance from the stocking point and only moderately negatively related to density. We conclude that the results of egg stocking can be difficult to interpret because site-specific density may vary with distance from the stocking point and the number of eggs stocked.