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ABSTRACT 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. [ABSTRACT FROM AUTHOR]

ABSTRACT Regional factors correlated with recruitment of black bass (largemouth bass; Micropterus nigricans and smallmouth bass; Micropterus dolomieu), two important fishes, are rarely studied, despite the importance of recruitment variation in influencing fish populations. We sought to identify factors that drove variation in age‐0 and age‐1 black bass abundance. Age‐0 or age‐1 black bass catch per unit effort (CPUE) in reservoirs in Kansas and Illinois, USA, was positively correlated with local short‐term (i.e., mean April precipitation) environmental variables. In contrast, age‐0 or age‐1 black bass CPUE was generally negatively correlated with long‐term environmental variables and river regulation metrics (i.e., reservoir elevation) in the Mississippi and Missouri river reservoirs. Our findings highlight that consideration of spatiotemporal scale is important when managing black bass populations. [ABSTRACT FROM AUTHOR]

Abundance of adult walleye (Sander vitreus) and sauger (Sander canadensis), two important sport fishes, decreased significantly during 2001–2022 in Lewis and Clark Lake, a border water between Nebraska and South Dakota, despite walleye fingerling stocking and stable age‐0 abundance of both species. We sought to identify factors that drove variation in age‐0 abundance from 2001 to 2022 using an information theoretic approach. Age‐0 walleye catch per unit effort (CPUE) was correlated to mean monthly outflow, mean annual precipitation, and mean April gauge height in a delta. Age‐0 sauger CPUE was correlated to adult conspecific CPUE, mean April Heating Degree Days, and mean annual precipitation. Our findings suggest that both biotic and abiotic factors were important for explaining variation in age‐0 CPUE of sauger, but mainly abiotic factors for walleye. As such, manipulation of abiotic factors (i.e., outflow) by installing entrainment barriers may be more effective than manipulation of biotic factors (i.e., stocking). [ABSTRACT FROM AUTHOR]

Paddlefish, Polyodon spathula (Walbaum), provide an important snagging and bowfishing fishery below Gavins Point Dam in South Dakota. During 2009–2020, snagging catch rates of paddlefish decreased below Gavins Point Dam to presumed "normal" lower pre‐2004 levels, while bowfishing catch (harvest) rates significantly increased during 2000–2020. Because Paddlefish are highly migratory, both local (i.e., monthly gauge height, precipitation, and air temperature near Gavins Point Dam) and remote (difference in Mississippi and Missouri River discharge near their confluence) environmental conditions were used to explain variation in snagging catch rates and bowfishing harvest rates. Snagging catch rates were related to October gauge height, whereby deeper water in October led to decreased catch rates below Gavins Point Dam. Bowfishing harvest rates increased significantly after a 2016 regulation change moved the season from July 1 to July 31, and from June 1 to June 30, likely because water clarity was greater in June than in July. Mean annual air temperature and precipitation explained variation in bowfishing harvest rates prior to the 2016 regulation change. Our findings, the first to examine both snagging and bowfishing fisheries below Gavins Point Dam, suggest that local abiotic factors are likely more important than remote discharge for explaining variation in snagging catch rates and bowfishing harvest rates in the channelised Missouri River. [ABSTRACT FROM AUTHOR]

The brown trout, Salmo trutta L., population in River Skjern, a major tributary stream to the Danish lagoon Ringkøbing Fjord, is reduced despite various efforts towards its recovery. This study investigated if bycatch of migratory trout in the commercial whitefish, Coregonus lavaretus L., fishery in the lagoon might be a significant cause. Experimental surveys were carried out to examine bycatch levels using different fishing protocols and gear types. Data were also collected through an observer fishery, questionnaires and from a database on local fisheries statistics. Trout occurred as bycatch in low numbers in the observer fishery (mean of 0.2 trout per km gillnet). The whitefish fishing protocols examined in the experimental surveys revealed a significantly lower bycatch of trout when fishing with sinking gillnets than floating gillnets. However, few fishers use floating gillnets in the present‐day fishery. The other fishing practices examined revealed no alternatives that would reduce trout bycatch markedly. The results indicated that the whitefish fishery in the lagoon is not the major reason for the lack of recovery of the trout population in River Skjern. [ABSTRACT FROM AUTHOR]

The age‐0 abundance of eight sport fish species in the four mainstem Missouri River reservoirs in South Dakota was evaluated to estimate the influence of environmental and biological factors on age‐0 species abundance. Datasets (at least ten consecutive years) from each reservoir were analysed to evaluate the effects of both monthly (i.e. gauge height, temperature and precipitation) and annual (i.e. cooling degree days and heating degree days, minimum, average, and maximum temperature, and average precipitation) environmental and biological factors. Biological factors including age‐0 prey fish abundance (i.e. gizzard shad Dorosoma cepedianum [Leseuer] abundance), age‐0 sport fish abundance and adult sport fish abundance were examined. Factors were included that are known to have impacts on abundance of age‐0 sport fish in other systems. The abundance of all sport fish species was stable or increasing in all reservoirs, except for walleye Sander vitreus (Mitchell) and white bass Morone chrysops (Rafinesque) in Lewis and Clark Lake. Age‐0 white crappie was the most supported model for explaining age‐0 walleye abundance in Lewis and Clark Lake, and adult white crappie abundance was the most supported model parameter for explaining age‐0 white bass abundance in the reservoir. Findings of the current study highlight the need for species‐specific management of both environmental (i.e. flow manipulation) and biological factors (i.e. harvest limits for sport fish) to increase the abundance of age‐0 sport fish. Due to the dynamic nature of aquatic systems, resulting requirements for management agencies are system‐specific evaluations and management approaches. [ABSTRACT FROM AUTHOR]

Almost all fisheries in the Zambezi River system have experienced severe declines in catch rates, loss of larger, most valuable fish species, and increased use of environmentally damaging active fishing gears. The fisheries of the Barotse, Caprivi and Kafue floodplains, and lakes Kariba (Zambian sector), Malawi and Malombe are all fished down. The concept of balanced harvesting with moderate effort has no relevance to these African inland fisheries, where rapid human population growth and lack of alternative livelihoods for small-scale fishers means they have no choice but to continue fishing despite dwindling returns. In some areas, e.g. Liuwa Plain National Park in Zambia and conservancies in Namibia, comanagement with local communities has potential for success, but other fisheries, e.g. Lake Malombe in Malawi, are so severely fished down that there is no prospect of recovery without radical restructuring of exploitation patterns coupled with habitat restoration. [ABSTRACT FROM AUTHOR]

The characteristics and contribution of a developing recreational fishery to the local, regional and national economy of Angola were evaluated in 2006. Annual angling effort was 13 435 h, while the estimated total catch of the three target species [leerfish, Lichia amia (L.), west coast dusky kob, Argyrosomus coronus (Griffiths & Heemstra) and shad, Pomatomus saltatrix (L.)], was 5913 fish with a mass of 27 975 kg. Catch per unit effort (CPUE) for all teleost species combined was 0.44 fish per angler h−1 and 2.08 kg per angler h−1. Total harvest of the three species was 576 fish with a total mass of 2221.6 kg. The total contribution of this recreational fishery (mostly anglers from South Africa) to the local economy was US$ 1007 per harvested fish and US$ 243 per harvested kg. This equated to a contribution to the local, regional and national economies of US$ 151 685, US$ 44 767 and US$ 344 364 respectively. Although the regional contribution was less than half of the national contribution, it was regionally significant when the low population density and the general absence of other formal sector employment opportunities are considered. As a result of the largely undisturbed nature of the southern Angolan coastline, the catch, effort and CPUE information was considered suitable as a baseline for a cost-effective method of future fisheries monitoring in the region. [ABSTRACT FROM AUTHOR]

Abstract Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha-1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha-1 yr-1 . The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f ) and the catch-per-unit-effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long-term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries. [ABSTRACT FROM AUTHOR]