Fisheries Management and Ecology最新文献

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.

Resource user compliance is a key element in effective fisheries management. Herein, we examine two decades of enforcement records pertaining to Atlantic salmon from Newfoundland and Labrador, Canada. Illegal incidents were negatively correlated with the number of licensed anglers but not salmon abundance. Over two decades, illegal incidents declined by 66%, even after correcting for the positive relationship between enforcement effort and illegal incidents. This decline was primarily driven by a 67% reduction in netting and jigging-related violations, which were likely to impose the highest levels of mortality on adult salmon among violations examined. Additionally, illegal incidents and violation types did not increase as a result of management changes. While Newfoundland and Labrador remains one of the last strongholds for Atlantic salmon, we encourage other jurisdictions to monitor fisheries compliance to better understand the social-ecological landscape that is crucial to supporting healthy fisheries.

Estimating egg deposition for Atlantic salmon population assessments is made difficult by their lack of sexual dimorphism prior to the autumn spawning season. We quantified the effect of sex misclassification from subjective examination of external morphology on egg deposition estimates in four Atlantic salmon populations across multiple years. Sex classification of Canadian salmon using the genetic sex marker (sdY) was accurate (>97%), whereas sex classification based on subjective examination of external morphology was inaccurate, with misclassification rates dependent on sea age, life history, and sampling season. Sex misclassification led to annual egg deposition estimates that ranged from −36% to +56%. We found that sex could not be discriminated based on measures of external morphology.

Stocking is one of the foremost tools in the inland fisheries management toolbox, but it comes with both opportunities and risks. Stocking is often used as compensation for depleted wild populations, particularly where recruitment processes have been disrupted, but it can introduce disease, disrupt community structures, reduce genetic integrity, and cause conflicts between fishery stakeholders. Despite its widespread use, examples of effective stocking for food fisheries in inland waters are sparse in the peer-reviewed literature. Nevertheless, it is well established that stocking is frequently used to maintain fish yield, so there is a need to conduct the practice in a robust manner that minimises the potential risks. This paper serves as the front matter for a special section of Fisheries Management and Ecology focused on fresh waters feeding the world, which resulted from two panel sessions, one focused on aquaculture and one focused on stocking, hosted by the international InFish research network (https://infish.org/). The paper highlights current practices of fish stock enhancement in inland waters for food, examines potential synergies and interactions of stock enhancement programmes with aquaculture, and provides an outline framework for responsible management of fish stock enhancement.

Effects of global climate change on inland artisanal fisheries have received little attention from scientists. We investigated fisheries of the Lower Amazon in Brazil using a wavelet analysis of a 13-year data series of fishery catches, environmental variables, and climatic indices, to determine how these variables affected catches of different species. The catch per unit of effort (CPUE) of gillnet and line fisheries increased over time. Relative humidity, latent heat, and sea surface temperatures influenced productivity of both fisheries. El Niño had a negative and immediate effect on gillnet CPUE, while its effect on line fishing was positive, with an eight month lag. Our findings indicate that fishery productivity was modulated by climate events, which influenced ecosystems and modified habitats and ecological niches, andthereby impacted fishery productivity.

Coregonines (ciscoes and whitefishes) are economically, ecologically, and culturally important fishes that are distributed throughout the Northern Hemisphere. In the Laurentian Great Lakes, coregonines declined throughout the 19th and 20th centuries, and managers have prioritized their restoration. A key restoration tool is reintroduction via stocking. However, hatchery-reared coregonines can display different morphologies than wild fish, which could affect their fitness. Unfortunately, our understanding of these differences is limited because previous work did not adequately remove allometric effects in morphological analyses. We compared morphologies between wild and hatchery-reared Bloater (Coregonus hoyi) from the same stock using appropriate size corrections. Hatchery-reared fish had shorter heads, shorter dorsal fins, and shallower bodies than wild fish. Moreover, some characters differed across wild fish collections. Our results improve our understanding of how artificial rearing can impact coregonine morphology, and we recommend future studies on what causes these differences and whether they impact fitness.