Fisheries Management and Ecology最新文献

Hatcheries have long produced salmonids for fisheries and mitigation, though their widespread use is increasingly controversial because of potential impacts to wild salmonids. We conducted a global literature search of peer-reviewed publications (1970–2021) evaluating how hatchery salmonids affected wild salmonids, developed a publicly available database, and synthesized results. Two hundred six publications met our search criteria, with 83% reporting adverse/minimally adverse effects on wild salmonids. Adverse genetic effects on diversity were most common, followed by effects on productivity and abundance via ecological and genetic processes. Few publications (3%) reported beneficial hatchery effects on wild salmonids, nearly all from intensive recovery programs used to bolster highly depleted wild populations. Our review suggests hatcheries commonly have adverse impacts on wild salmonids in freshwater and marine environments. Future research on less studied effects—such as epigenetics—could improve knowledge and management of the full extent of hatchery impacts.

The migratory behavior and spawning of Curimatá-pacu (Prochilodus argenteus) were assessed in a free-flowing remnant spanning approximately 450 km. This evaluation was conducted using radio-tagging and egg sampling, with identification performed through metabarcoding techniques. Among the studied individuals, half migrated 100–365 km upstream, primarily in response to the initial rise in river discharge at the onset of the wet season. Conversely, the remaining fish did not exhibit upstream movement, indicating a partial migratory behavior. The presence of eggs exclusively in the headwaters suggests that breeding occurred solely among fish inhabiting the upstream sites. The observed migratory traits resembled those of other congeneric species.

We sought to demonstrate how eel mortality, growth, and biomass production were related to initial stocking density of glass eels, 18 months after stocking. Glass eels with a mean body mass of 0.29 g were caught in three coastal streams of Denmark, and subsequently stocked at four densities (0.5, 1, 1.5, and 2 individuals m⁻²) in eight shallow, 200 m², open ponds. Recapture after 18 months ranged from 13% to 84% and was negatively correlated with stocking density. Likewise, growth (length and body mass) and body condition were negatively correlated with stocking density. The theoretical maximum biomass per stocked glass eel was 7.3 g at a density of 0.005 eels per m⁻² (one glass eel per pond), and the minimum was at a density of 3 glass eel m⁻² (600 glass eels per pond). The optimum eel biomass was 3.9 g m⁻² at a stocking density of ≈1 glass eel m⁻², which probably represented the present production capacity (food) of these ponds.

The Acoupa weakfish, Cynoscion acoupa, is an important fishery resource of the Brazilian North coast that is commercially valuable, particularly for its gas bladder (fish maw), which is exported to Asian markets. However, because of intensive fishing and lack of reliable data, the Acoupa weakfish is classified as Vulnerable by the IUCN. We used Fisheries Performance Indicators (FPIs) to evaluate C. acoupa fisheries on the Amazon continental shelf, to inform management actions. The ecological indicator had the lowest score due to increased fishing effort associated with high demand for the fish maw, and the co-management indicator was also unsatisfactory due to the predominance of fishing entrepreneurs and a lack of sustainable management practices. Our findings showed that the C. acoupa fishery is precarious in its sustainability, mainly because of harvest and co-management which were the least satisfactory metrics.

Stocking of marine fish into coastal systems to augment natural recruitment is a growing practice adopted by fisheries managers around the world. Releasing fish directly into well-resourced nursery grounds greatly increases survival and retention of stocked individuals but requires an understanding of juvenile habitat requirements. In eastern Australia, the dusky flathead (Platycephalus fuscus) is a highly regarded recreationally targeted species and the focus of an emerging stock enhancement programme, although little is known of their specific nursery habitat. Using acoustic telemetry, hatchery-reared juveniles were monitored in Lake Macquarie to quantify habitat use and dispersal. Sandy areas adjacent to edges of seagrass beds were favoured, likely as foraging habitat. Within 5 weeks after release, fish were detected 5 km from the release site, but only at locations containing seagrass beds, so stocked fish likely disperse around estuaries to regions with suitable habitat. Future releases of dusky flathead should target areas containing patchy seagrass-sand to optimise stocking outcomes. Beyond fisheries enhancement programmes, our findings highlight the importance of structured habitat, such as seagrass beds, for juvenile fish.

Accurate information on population structure is essential for effective fisheries management. Greenland halibut (Reinhardtius hippoglossoides) in the North Atlantic is managed as four separate offshore stocks. We use Multivariate Autoregressive State-Space (MARSS) models to assess population structure by means of abundance and biomass trends in four regions (Norwegian Sea, Iceland, Southeast Greenland, and Northwest Atlantic) where three offshore stocks are recognized: (1) Baffin Bay–Davis Strait (Northwest Atlantic stock), (2) Southeast Greenland and Iceland (West Nordic stock (WNS)), and (3) the Barents and Norwegian Seas (Northeast Arctic stock). We formulated model alternatives, using bottom trawl survey data from each region for 1996–2019, to evaluate support for different population structures. Abundance and biomass observations from each region were linked to growth rate parameters in MARSS models and the impact of climate (North Atlantic Oscillation Index) and fishing (commercial catches) on stock dynamics was investigated. Top models identified the Northwest Atlantic as an independent population. Best-fit models treated Greenland halibut in the WNS as two independent populations (east and west), with potential connections between eastern Iceland and the western Barents Sea. These results suggest a mismatch between current stock perception and management boundaries in the Northeast Atlantic.

Evaluating population trends in dynamic estuarine environments can be challenging, especially when survey data include a high percentage of zero observations. In fishery-independent surveys, zeros that come from reduced susceptibility to sample gears and reduced availability of the population to the survey impact survey catchability and negatively bias relative abundance indices. A zero-inflated negative binomial model was used to standardize a juvenile Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) relative abundance index (Hudson River, New York) that included a high proportion (42%) of zero observations and intra- and interannually variable covariates. Reduced susceptibility was related to low water temperature, with the percentage of zeroes increasing rapidly below 7°C. Availability was influenced by temperature and distance to salt front, as catch rates increased with temperature and peaked in mesohaline waters ~27 km downstream of the predicted salt front. An alternative index suggested significant population growth (r = 0.15; p-value = 0.007) occurred from 2004 to 2015. The zero-inflated model helped better understand Hudson River juvenile Atlantic Sturgeon ecology and relative trends in abundance, to better inform future management and monitoring decisions along the Atlantic Coast.

Size-based indicators are appropriate for monitoring status and guiding management of multi-species, multi-gear fisheries, such as coral reef fisheries. From May 2018 to April 2019, size distribution and composition of coral reef fish catches were monitored through a participatory landing survey in southwestern Madagascar. Fishers targeted a large diversity of fish taxa (75 families) and range of sizes (1.6–86 cm). Five predominant gears accounted for most of the catch (1360 [±39] t), including mosquito net trawl (27.7%), beach seine (26.8%), speargun (7.2%), gillnet (30.6%), and handline (7.1%). Due to widespread use of gears made from mosquito nets, 75% of fishes smaller than 9 cm and 47% of juvenile fishes were represented in the total catch number. Large-size taxa (Scaridae, Lethrinidae, Siganidae, Acanthuridae, Synodontidae, Mullidae, and Labridae) were mostly harvested as juveniles. Catches varied by 8%–70% throughout the year. Size of coral reef fish, annual catches, and catch rates all declined since the 1990s.

Groupers are apex predators that are believed to play crucial roles in ecosystems, so any loss or decline of these species in coral reefs can adversely affect ecosystem stability. Epinephelus fuscoguttatus is currently categorized as vulnerable (VU) from its previous near threatened (NT) category. Information about their biological and ecological status is limited to assist in formulating management plans for the species in Kenya. Therefore, we aimed to provide baseline scientific information on the biology of E. fuscoguttatus, to enable formulation of sustainable management strategies. Sampling was conducted for 1 year at two fish landing sites along the Kenyan coast: Shimoni and Mayungu. Exploitation rate, size at maturity (L₅₀), GSI, and fecundity were estimated. We found that E. fuscoguttatus was currently exploited above an optimum level, (E = 0.9). Length at maturity L₅₀ was 59.50 cm for males and 48.2 cm for females, and mean fecundity was 509,121 eggs/female/year. The gonadosomatic index was highest in June and December, but ripe females were identified in several months to suggest a protracted spawning period. The exploitation rate of E. fuscoguttatus was not sustainable. Consequently, we recommend reducing fishing effort to biologically sustainable levels to enhance recovery.

Fish are ubiquitous in pumped artificial drains but channel maintenance exposes fish to high flows and predators, and fish communities may experience population-level threats if they are unable to access refuge during extreme flood-relief pump operations. We assessed the impact of an extreme flood-relief pump operation and effects of artificial habitat introduction on a resident fish community in an artificial drain in Great Britain using side-scan and multi-beam sonar. Sonar surveys before the flood found abundant aggregations of resident fish, whereas no fish were found after the flood, which suggested flood-relief pump operations significantly altered resident fish populations. Fish abundance near artificial habitats monitored before the flood were highest during crepuscular periods and was similar among three different artificial habitat designs. Our findings improve the understanding of extreme flood impacts on fish in artificial drains and demonstrate the usefulness of sonar techniques for surveying abundance and spatial distribution of fish populations before and after floods.