Fisheries Management and Ecology最新文献

Gillnets are the most commonly used fishing gear targeting black rockfish (Sebastes schlegeli) and fat greenling (Hexagrammos otakii) in the artificial reef area in coastal China. However, a minimum mesh size (MMS) has not yet been established for this fishery, which is unfavorable for sustainable development and effective management of fishery resources. We compared size selectivity and catch efficiency of gillnets of four commonly used mesh size (stretched mesh size; 40, 50, 60, and 70-mm) in a typical artificial reef area in the Yellow Sea, China. Increasing the mesh size improved size selectivity of gillnets for black rockfish and fat greenling by reducing the proportion of undersized individuals. Further, changes in mesh size affected catch efficiency of target-sized individuals. To protect juveniles, while maintaining catch efficiency for target-sized fish, we recommend 60-mm as the MMS for this fishery. Our study will contribute to the development of MMS regulations in reef fisheries management in China.

Rainbow trout have been translocated from North America worldwide for more than 150 years, but have not reproduced in the wild in Europe in the last 100 years. In recent decades, several examples of successful reproduction have become public. This study reports scientific evidence of natural reproduction of North American rainbow trout (Oncorhynchus mykiss) in three alpine rivers in Bavaria, Germany. Eggs collected from spawning redds were determined to be rainbow trout in all study rivers. In the river Leitzach, where spawning was exclusively observed in spring, electrofishing revealed a balanced length-frequency distribution with a high abundance of rainbow trout and a high proportion of individuals < 10 cm. In the rivers Isar and Traun, spawning was observed in winter and supposedly also in spring, according to local reports. Rainbow trout < 10 cm were also observed in these two rivers during electrofishing surveys but were less abundant than in the river Leitzach. Genetic factors and river-specific environmental and climatic conditions may have contributed to the success or failure of rainbow trout reproduction. Effects of rainbow trout on native fish vary widely, from severe negative impacts to minimal niche overlap, so further studies of genetic and environmental factors that determine rainbow trout naturalisation are needed to better inform fisheries management.

Catch-and-release (C&R) angling is becoming more common worldwide for managing stream-resident salmonids but has only recently been introduced in Japan. However, few studies have examined effects of C&R regulations on fish populations through adequate experimental designs. We estimated effects of implementing a C&R regulation on stream-resident salmonids. The western part of the Agatsuma River system in Japan is a fishing area with standard regulations under which anglers can harvest white-spotted charr or masu salmon of > 15 cm total length. In contrast, the eastern part is a fishing area with a C&R regulation requiring release of all caught fish, owing to radiocesium contamination caused by a nuclear accident at Fukushima. Density and total length of stream-resident salmonids were examined in these areas in several tributaries. Fish density was significantly higher in the C&R area, whereas total length did not differ significantly between areas. Implementing a C&R regulation may be effective for conserving salmonid populations in mountainous streams.

The cobia (Rachycentron canadum) is important to fisheries in Northeastern Brazil. To restore stocks in Rio Grande do Norte, cobia were stocked and the fishery was monitored over 4 years. We evaluated effects of stocking on cobia size composition in this data-limited fishery to understand stocking limitations and explore possibilities for future projects. Total length of cobia was significantly shorter after stocking than before stocking, with mostly small fish caught mainly by nets, an unusual pattern for cobia. Total length also varied significantly among bottom types. Most of the cobia harvested were below the size at first maturity, which suggests that stocking increased the catch, but most fish harvested were immature, thereby potentially hindering stock recovery. For future projects, we recommend against the use of plastic tags for tagging hatchery cobia and propose releases that emulate natural spawning dynamics, alongside releasing fish at older ages. Further, we recommend robust post-stocking fishery monitoring, and management strategies, such as a release of net-caught cobia in the initial 2 years and incorporating validated fisher knowledge into decision-making.

To reduce catches of juvenile bigeye and yellowfin tuna, while maintaining skipjack catches under drifting fish aggregating devices (dFAD), we analyzed spatiotemporal distributions of dFAD catches by European purse seiners in the Eastern Atlantic Ocean during 1996–2019. To detect hotspots of juvenile dFAD catches, we: identified periods of maximum abundance using a seasonal sub-series diagram; normalized monthly FAD catches per unit effort; and used emerging hotspots analysis on spatiotemporal density. Two main spatiotemporal strata were identified in the Guinean Gulf, which could be used to establish moratoria on dFAD fishing. These spatiotemporal strata differed from the existing ICCAT moratorium, which spanned a larger part of the African coast. Our findings also indicated that time-area closures of dFAD-fishing lasting 3–4 months in smaller areas could be more effective than the current dFAD moratorium to reduce unwanted bycatch in the Eastern Atlantic region. The two metrics we developed for comparison provided clear and measurable evidence that demonstrated how strategic and data-informed moratoriums can lead to substantial improvements in conservation.

Citizen science platforms are an alternative to traditional survey methods for collecting data from recreational fisheries. However, to supplement data collection, challenges associated with these platforms must be addressed, such as lack of recruitment and sustained engagement. Some platforms distinguish between recruitment and data contribution in that participants might register on a platform, but only a subset starts contributing data, and even fewer continue to do so. To further understanding of drivers behind data contribution, we first assessed the willingness to share information, using response rates to optional questions asked during account registration, among three distinct groups of participants on an electronic citizen science platform for anglers: (i) registered and did not contribute data (registrants); (ii) registered and contributed data in a single year (contributors); and (iii) registered and contributed data in multiple years (sustained contributors). We next modeled demographic and fishery-specific questions to determine specific drivers of data contribution and sustained contribution. Willingness to share information upon registration was lowest among registrants, intermediate among contributors, and highest among sustained contributors. The answer to the question “How important is angling as a hobby for you?” was the main driver in moving from registrant to contributor and from contributor to sustained contributor (i.e., participants who considered angling a more important hobby were more likely to be contributors and sustained contributors). Additionally, the probability of being a contributor declined over time, and angler residence (postal codes) was a driver of sustained contribution. Our findings indicated temporal and spatial instability in the participant base.

Aquatic protected areas and co-management have been proposed as strategies for conserving fisheries resources in several world regions. We analyzed the effects of different levels of governance on yield of experimental fisheries in Amazonian floodplain lakes. Sampling between 2018 and 2022 used gill nets deployed for 24 h during flooding and receding water phases. Generalized linear models (GLMs) were fitted to catch per unit effort (CPUE) and covariates, river level, time, sampling sites, level of management of the collection sites, and lake fishery management type. CPUE was significantly related to governance, management type, sampling site, and water level. Our results indicated that areas of sustainable use where community-based co-management was implemented were more effective for promoting high fishery yield.