Fisheries Management and Ecology最新文献

Identifying efficient otolith subsampling strategies that maintain data quality for stock assessments is imperative given limited resources to meet age-estimation demands of managed fish stocks. Our objective was to evaluate the performance of three different subsampling strategies: (1) fixed otolith subsampling, (2) proportional otolith subsampling with targeted supplemental sampling, and (3) hybrid otolith sampling for estimating age composition and proportions of individuals-at-age within length bins for Pacific sardine (Sardinops sagax). Proportional and hybrid strategies generally performed better than the fixed strategy. The performance of subsampling strategies was less consistent among combinations of age and length bins for estimates of proportions of ages-at-length than for estimates of age composition, due in part to high variation in age-at-length that caused uncertainty in predicted ages from lengths. We recommend the hybrid strategy that increases sample sizes at extremes of the length distribution and within length bins with multiple age classes. Processing 300–500 otoliths per year for age estimation is expected to maintain accuracy and reliability.

Most research comparing wild and hatchery-produced fish focuses on recently stocked individuals. As a result, these studies only investigate the behavior of naive hatchery fish, leaving a knowledge gap regarding long-term survivors. We compared the movement, space use, and survival of wild and hatchery-reared brown trout (Salmo trutta) that had survived for multiple years in a large Swedish lake (345 km²). Acoustic tracking of 38 wild and 56 naturalized, hatchery-origin trout over 4 years revealed similar weekly travel distances, sub-basin transitions, and survival rates between the groups. However, wild trout exhibited greater seasonal variability in their movement and sub-basin usage than their hatchery-reared conspecifics. These differences may reflect a reduced ability of hatchery trout to respond to environmental cues (e.g., prey availability). Our findings highlight that while hatchery-reared trout can persist in the wild, behavioral differences may influence their local ecological interactions and long-term fitness.

In 2002, the Brazilian government banned fishing for Goliath grouper, Epinephelus itajara (Lichtenstein, 1822), through 2007. This grouper was the first fish species targeted by a specific law in Brazilian environmental legislation. Grouper stocks showed no signs of recovery, so the ban was renewed multiple times since 2007. Official estimates indicated that catches of Goliath grouper from the Amazon continental shelf decreased by ~70% since the moratorium was instituted, although this may be an underestimate because actual catches were likely underreported prior to the ban. We investigated fisher behavior while fishing illegally for Goliath grouper, based on fisher perceptions and current fishery management in Brazil. In particular, we investigated underlying social and economic motives for illegal fishing by local artisanal fishers. We used a quali-quantitative approach to document fishing scenarios, identify problems associated with illegal fishing, and develop approaches for constructive measures to effectively manage Goliath grouper stocks. Productivity and susceptibility analysis (PSA) and cluster analysis identified positive and negative behavioral attributes related to illegal fishing by fishers from the Amazon coast. Fishers expressed moderate to negative profiles of sustainability in relation to the moratorium and illegal fishing for Goliath grouper, which reflected the ineffectiveness of the current management system, proposed more than 20 years ago. A more viable and effective management approach should balance legislation with the reality of artisanal fisheries. Therefore, we propose integrating more holistic measures with intervention that seeks fairer and more positive measures of control that involve motivated local actors.

The Murray-Darling Basin (MDB) is one of the most regulated and fragmented river systems in Australia. The basin's extensive river infrastructure development has supported growing water demands for irrigation, industry, domestic, and electricity production, but increased use of pumps for water diversion threatens aquatic species and biodiversity conservation. Of particular concern is the entrainment of fish from natural waterways into water intake infrastructure, which causes the loss of millions of fish every year in the MDB. Fish protection screens have been installed to prevent fish entrainment, but few studies have empirically evaluated their effectiveness, and none in Australian rivers. We investigated the effectiveness of fish screens in reducing the entrainment of multiple aquatic species and debris at differently sized discharge pump diversions in Australia. Screening pumps reduced fish entrainment by 93%–100% and debris entrainment by over 99%. When appropriately designed and operated, fish screens reduced fish, crustacean, and debris entrainment by small and large water pumps in multiple riverine environments. Impingement of organisms at screen installations requires further investigation. We recommend fish protection screens as a complementary tool for supporting native fish recovery and river management programmes, while still enabling an effective water supply for human needs.

Fishing tourism of sailfish and accompanying species represents a significant source of income for Costa Rica. However, little information is available regarding trends in the availability of these species to recreational fleets. We estimated temporal trends in catch per unit effort (CPUE) for sailfish, marlins, yellowfin tuna, and mahi mahi using recreational fisheries data from the central and south Pacific coast of Costa Rica during 2011–2023. The CPUE declined for sailfish but increased or remained stable for the other species. The decrease in CPUE for sailfish was correlated with an increase in commercial longline sailfish landings and, to a lesser extent, with sea surface temperature (SST). The increase in CPUE for the other species was positively correlated with SST and with commercial landings, except for tuna. Our results suggest that local commercial fisheries and environmental variability are affecting the availability of sailfish for the recreational fishery. We strongly suggest that our findings be included in national fisheries management initiatives.