Fisheries Management and Ecology最新文献

The Atlantic chub mackerel (Scomber colias) became an important resource in purse-seine fisheries of the Iberian Peninsula in the mid-2000s. Being data-limited at the stock level, 60 years of landings and 40 years of bottom-trawl survey data were available for part of the area. A biomass model fitted to landings and survey data performed well under the assumption of homogeneous dynamics across the stock area. During 1993–2020, relative stock biomass was above potential reference points with wave-like variation and peaks in 1995 and 2008. Credible intervals of relative fishing mortality indicated that exploitation may have been unsustainable since 2012. Chub mackerel productivity increased from the 1980s to the 1990s, possibly due to decreased sardine predation and competition and increased larval growth. The approach we used demonstrated how information from a portion of a stock's distribution area can be utilised for stock assessment, to potentially prevent neglect of stock data or alteration of management units.

Parasitological information may be useful for managing economically important fisheries by providing insights into population dynamics and health effects. The Chinook salmon (Oncorhynchus tshawytscha), an invasive species with high socio-ecological importance in South America, supports recreational and incipient artisanal fisheries. In Southern Chile, the recent approval of coastal fisheries for returning Chinook salmon in some regions highlights the importance of understanding salmon foraging, habitat use, and commercial value. However, such information is lacking. Parasites have been extensively used as cost-effective biological tags to identify fish stocks. We conducted the first parasitological examination of the marine tapeworm Hepatoxylon trichiuri larvae in returning adult Chinook salmon from the Cisnes River to assess its potential as a biological tag for returning Chinook salmon in Patagonia. Of 61 Chinook salmon from the Cisnes River, 52.46% were infected by H. trichiuri, with 1.65 ± 1.26 parasites per infected salmon (mean ± SD). Infection prevalence and intensity did not differ significantly between males and females. Infection intensity was higher in larger salmon but decreased with increasing salmon condition. Infection intensity was not significantly related to length, mass, or body condition. Infection prevalence and intensity of H. trichiuri varied spatially among Patagonian river-basin populations of Chinook salmon, thereby supporting the use of H. trichiuri as a biological tag. Our findings provide important parasitological metrics that may enhance future management practices by informing geographic variability in foraging locations of adult salmon and their commercial value for human consumption.

We employed a social-ecological systems (SES) framework to investigate the interplay of social and ecological factors influencing the sustainable management of common pool resources, the Sundarbans mangrove forest region in Bangladesh as a case study. Through qualitative and quantitative analyses, we identified positive and negative correlations between dimensions of the SES. Four positive and two negative correlations between dimensions of social systems and ecological systems highlighted the interconnectedness of dimensions in the SES framework. Our study only considered spatial variation across the four SES dimensions, which revealed distinct management practices within the region. Our findings underscored the importance of tailored management strategies to address specific SES dimensions. Enhanced stakeholder participation and institutional frameworks could bolster governance systems and actor capacity, while interventions targeting ecosystem health and species populations may improve sustainable resource systems and resource unit capacity. Our findings provide insights for policymakers and practitioners who seek to promote the sustainability of small-scale fisheries within SES contexts.

Anthropogenic structures, such as dams, delay, injure and kill during downstream migrating silver-phase Anguillid eels. To enhance spawner escapement from rivers, efforts are being made to develop devices that guide eels towards safe passage routes. We tested the ability of a strobing light array to deflect downstream migrating European silver eels (Anguilla anguilla) by comparing the distribution of eel catches in a series of nets when lights were on (treatment periods) and off (control periods). Deflection efficiency of the light array was 80.6% (95% CL = 74.3%–85.3%), estimated by comparing the proportion of the total biomass captured in nets located immediately downstream of the light array during control and treatment periods. Eels caught during treatment periods (Mean ± S.E.; 452 ± 11 mm) were significantly smaller than those caught during control periods (538 ± 8 mm), which suggested that smaller eels were less capable of avoiding the light array. Future research should determine specifications for operation of strobe light arrays, including effects of light intensity and strobe rate, angle of array deployment, and effects of environmental factors on deflection efficiency.

This study aimed to identify best-practice methods and equipment for humane dispatch of 15 species of sharks commonly captured by commercial fishers in the Northern Territory (NT), Australia. Anatomical brain location was determined for each species using dissection, external photographs and radiographs (see www.ikijime.com website and Ikijime Tool phone apps). Eight dispatch methods were qualitatively evaluated for their effectiveness on sharks of various sizes. Electrical stunning equipment could not be used because it failed to meet Australian electrical safety standards. Field trials of 206 dispatch events found that penetrating captive bolt tools were most effective on medium-sized (120–210 cm) and large sharks (210–360 cm long), with mean total dispatch scores (MTDS) that ranged from 4.6 to 4.84 out of 5 and instantaneous death rate (IDR) that ranged from 88.57% to 95.45% (n = 79), while ikijime was most effective on small sharks (< 120 cm long), with an MTDS of 4.69 and IDR of 93.75% (n = 16). In contrast, percussive stunning (MTDS = 3.95, IDR = 80.95%, n = 42), shooting with a 12-gauge shotgun (MTDS = 2.92, IDR = 36.54%, n = 52) and spinal section (MTDS = 3, IDR = 0%, n = 2) were less effective, as shown by their lower IDR and MTDS scores. These preliminary findings may be useful for directing further research into best-practice dispatch methods for sharks in the NT, Australia, and elsewhere globally.

Climate change has significantly affected the Curonian Lagoon, the largest coastal lagoon in Europe, which is of great economic importance to fisheries and tourism. We modeled how environmental factors and fisheries affected recruitment and subsequent catches of pikeperch (Sander lucioperca L.) and common bream (Abramis brama L.) in the lagoon. Recruitment, catch per unit effort (CPUE), environmental variables, and fishery catch, and effort were used to construct Bayesian belief networks (BBNs) for both fish species. Catches of pikeperch and common bream depended more on fishing effort than recruitment. Environmental factors (temperature and riverine discharge) were only weakly related to catches of pikeperch and common bream. Changes in salinity and temperature are expected to have only minor direct effects on populations of pikeperch and common bream.

Although the worldwide status of burbot (Lota lota) across its Holarctic distribution has recently been assessed, adverse effects of dreissenid mussels on burbot abundance in waters invaded by mussels have not been investigated. We analyzed data from an annual spring gillnet survey to characterize burbot population dynamics in northern Lake Michigan during 2001–2023. Adult burbot abundance in northern Lake Michigan trended neither significantly upward nor downward during 2001–2023. Thus, expansion of the quagga mussel (Dreissena rostriformis bugensis) population into deeper waters of Lake Michigan during 2003–2008 had no detectable negative effects on burbot abundance. Burbot continued to feed on lake trout (Salvelinus namaycush) stocked in the Northern Refuge of Lake Michigan through 2023, which supported a hypothesis that the burbot population potentially impeded lake trout restoration in the refuge.

The shortfin mako shark (Isurus oxyrinchus) is a widely distributed predatory species. However, critical aspects of its biology remain poorly understood in several regions, including the Ecuadorian Pacific Ocean, where it is one of the most commonly captured shark species. Vertebral samples of 238 specimens were analyzed, including 119 females (82–228 cm TL; 0–15 years), 115 males (76.4–248 cm TL; 0–16 years), and 4 unsexed individuals (194–215 cm TL; 10–14 years). The von Bertalanffy model provided the best fit for males (L_∞  271.31 cm TL, L₀ = 75.85 cm TL, k = 0.10 year⁻¹), and females (L_∞  347.53 cm TL, L₀ = 76.04 cm TL, k = 0.06 year⁻¹). The results indicated sexual dimorphism, with females reaching a larger size and exhibiting slower growth rates compared with males. The shortfin mako shark in the Ecuadorian Pacific Ocean grew slow, and based on its life history characteristics, is vulnerable to overexploitation, thereby necessitating harvest management to sustain a fishery.