Fisheries Management and Ecology最新文献

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).

Globally, aging offshore oil and gas (O&G) platforms face resource depletion, and regulations often demand platform removal through decommissioning. In the North Sea, >€90 billion will be needed for decommissioning by 2060. However, the influence of O&G platforms on fish communities is poorly understood. This challenges predictions of possible fisheries scenarios associated with different decommissioning options. Here, we examined the role that North Sea platforms played on fish communities. We explored patterns of fish abundance and body size variation along transects from O&G platforms comparing catch per unit effort data. Fish abundance was positively associated with O&G platforms. Atlantic cod, plaice, saithe, and mackerel were most abundant near platforms. Similarly, larger Atlantic cod were near the O&G platforms. Our study provided information for decision-making regarding platform decommissioning scenarios by evidencing O&G platform habitat provisioning for various commercial fish species.

We evaluated the feasibility of classifying ommastrephid and loliginid squid species by statolith shape analysis into fisheries management units or stocks. Statoliths of Illex coindetii (Verany, 1839) and Loligo forbesii (Steenstrup, 1856) were studied from multiple areas of the North East Atlantic and Northern Mediterranean Sea during 2021–2022. I. coindetii and L. forbesii individuals were categorized into multiple stocks across the areas studied. Stocks migrating between fishing areas as well as multiple stocks in the same area, as identified for L. forbesii in this study, need to be considered for sustainable fisheries management.

Coregonus populations across their Holarctic range have often undergone unexplained collapses. Here, we document causes of collapse for two of the largest Coregonus populations in the world, cisco (C. artedi) in Green Bay, Lake Michigan, and Saginaw Bay, Lake Huron, during the 1950s. We used simulation models, rank-order correlations, and historical literature to evaluate effects of overfishing, interactions with introduced rainbow smelt (Osmerus mordax), and overwinter bottom hypoxia on both cisco populations. Fully selected exploitation rates for cisco were alarmingly high (0.82–0.84), correlations and anecdotal evidence suggested negative interactions with rainbow smelt, and extensive areas of hypoxia coincident with cisco declines suggested incubation of cisco embryos was impaired regionally. Our findings suggested that negative effects of rainbow smelt were mainly responsible for the cisco population collapse in Green Bay and that overfishing and hypoxia had suppressed the Saginaw Bay cisco population before rainbow smelt caused its final collapse.

The Spanish mackerel (Scomberomorus brasiliensis) is of high commercial value throughout its distribution. In Northeast Brazil, this important fishery resource has been under strong fishing pressure since the 1960s, with length composition changing between 1998–2001 and 2020–2022. Length frequency distributions, exploitation indicators, and gear selectivity indicated the effects of overfishing on stock size structure, with excessive withdrawal of spawners and reduced numbers of adults larger than 60 cm in catches. In addition, gear selectivity changed, with reduced size at first capture in the 40-mm mesh. Our results indicated that the species is unsustainably exploited in the study area and suggested both growth and recruitment overfishing.

The Bagrid catfish, Bagrus orientalis, historically sustained communities in the Rufiji River basin (RRB), Tanzania, but has rapidly declined due to high consumer demand and unsustainable fishing. Consequently, a Ramsar site was designated within the RRB, although its potential to revitalize overexploited populations beyond its boundaries is uncertain because of limited information on genetic connectivity. To address this uncertainty, 158 partial cytochrome oxidase subunit I sequences of B. orientalis were analyzed to quantify genetic connectivity in the RRB. We observed significant genetic differentiation, indicating limited connectivity among populations. Populations in the Ramsar site were genetically connected to those in the Kilombero Valley Floodplain (KVFP), but were distinct from those in Ruaha and Rufiji, which clustered separately. Our findings suggested the Ramsar site could revitalize overexploited KVFP populations, and emphasized the need for sustained efforts against its encroachment. However, limited genetic connectivity with Ruaha and Rufiji implied that conservation measures in the site might have restricted effect in these areas. Conservation efforts should extend beyond the Ramsar site, by promoting sustainable fishing and enhancing habitat connectivity in Ruaha and Rufiji.

Across the globe, fish stocks have been in decline due to industrialization of fisheries resources, overfishing, pollution, and climate change, thereby warranting more fisheries assessments. The floodplain fishery of Tonle Sap Lake near the Kampong Khleang stilted community in the Chamkar Youn village in Cambodia was evaluated by: (1) characterizing fish assemblage structure and function, (2) highlighting temporal differences in fish assemblage, and (3) assessing potential indicators of fishing-down-the-food-web by the fishery. Fish trap data from the wet season were used to characterize fish abundance, diversity, species richness, and functional feeding guilds from fish catches in 2014 and 2019. Fish abundance declined 62% and species richness declined between 2014 and 2019. Smaller-bodied, lower-trophic level fishes dominated the catch. Our limited findings add insight into the status of a globally important fishery and highlight the need for more local collaborative fishery assessments.

Harvest strategies are utilised in the management of fishery resources globally. Critical to their success is harvest strategy evaluation, whereby future performance is assessed through projection modelling. Using the observed relationship between a puerulus settlement index and model-estimated recruitment, we evaluated a southern rock lobster (Jasus edwardsii) harvest strategy in South Australia. Short-to-medium puerulus settlement recruitment forecasting was incorporated into future projections of catch, catch per unit effort, and percent unexploited egg production (%UEP) during 2019–2022. Observed values of indicators that closely aligned with projected outputs indicated that puerulus forecasting underpinned reliable evaluation of future fishery performance. A key objective of the harvest strategy was to increase egg production in the fishery, with a 20% unexploited egg production targeted by 2036. The target was reached under the proposed strategy, but was sensitive to recruitment, thereby highlighting the need to consider climate change impacts in forecasting scenarios.

From a conservation standpoint, species that are managed without consideration of their population sizes and connectivity have the potential to be over-exploited and/or incur population decline. The burrowing shrimp, Trypaea australiensis, is an important ecosystem engineer and fishery resource caught in large numbers for which population information is unknown for properly managing the species. Here, we determined the level of population structure of T. australiensis across three locations along the East Coast of New South Wales, Australia, using genome-wide single nucleotide polymorphisms (SNPs) obtained through double digest Restriction-site Associated DNA-sequencing (ddRAD-seq). Analysis of population structure, including pairwise Fst (−0.003 to −0.001), STRUCTURE (K = 2) and Discriminant Analysis of Principal Components (DAPC) showed no evidence of structure among locations. Our findings provide crucial preliminary population genetic data for a key cryptic species, that also suggests gene flow among sampling locations enables the management of fisheries throughout the study area as a single unit.