Fish and Fisheries最新文献

Although the eco-evolutionary consequences of dispersal and exploitation are increasingly recognised, consideration of these effects and how they interact for management and conservation remains limited. We addressed this gap by examining population exploitation within a metapopulation framework, using Atlantic salmon as a case study. We compared eco-evolutionary consequences of alternative exploitation strategies by incorporating selective exploitation based on life-history traits and spatial dimension of exploitation (i.e., whether populations were net exporters or importers of individuals). We used a demo-genetic agent-based model to examine demographic and evolutionary consequences of these strategies across a gradient of population-specific exploitation rates. At the metapopulation scale, we found both lower abundance and earlier sexual maturation with increasing exploitation, particularly when fishing was selective on larger individuals. The spatial selectivity of exploitation had an overall additional detrimental effect on metapopulation performance and fisheries yield, and induced stronger evolutionary changes than when exploitation was evenly spread over all populations. We discuss the implications of metapopulation functioning for species management and how considering dispersal patterns and intensity might change how we apply harvest. Nevertheless, our findings suggest that the safest approach remains to distribute exploitation efforts evenly across all populations, especially in the absence of variation in intrinsic productivity. However, this strategy might not completely prevent negative consequences at the local scale. Therefore, we advise managers to critically assess the relevance of our results and dispersal assumptions in the specific cases they may have to deal with.

Social learning is common among vertebrates, including fish. Learning from others reduces the risk and costs of adaptation. In some longer-lived species, social learning can lead to the formation of persistent groups that pass learned adaptations from one generation to the next (culture). Variations in learned adaptations are subject to natural selection, leading to a second, fast-paced, fine-scale evolutionary process that complements genetics and enables adaptation to the peculiarities of local areas. Socially learned knowledge is stored mainly in the minds of older fish and subsequently inherited (learned) by younger fish. Consequently, the persistence of locally adapted groups of long-lived fish requires the inheritance of genetic and learned adaptations. Local populations of social learners are not often recognised nor conserved by fisheries managers. Fishing usually reduces the relative abundance of older fish far more than younger. We hypothesise that fishing may impair and eventually erase the learned local adaptations of long-lived fish, leading to the loss of local stocks of these species and significant ecosystem-wide changes. Fishing may shift abundance towards species not dependent on learned adaptations, i.e., invertebrates and short-lived fish. The hypothesis leads directly to the idea that conserving populations of long-lived social learners is likely best accomplished by protecting age and social structure or, more generally, the natural processes, such as social learning, that generate complexity in an adaptive ecosystem. Local area-based management is aligned with the local processes of social learners and can capture and learn about the effect of human activity at that scale.

Fjords provide valuable research opportunities for marine scientists. They are excellent natural infrastructure for climate impact studies associated with hypoxic episodes and consequences for mesopelagic and deep-sea ecosystems involving oceanographic circulation processes and basin water renewals. Repeated sampling from the same populations is possible, making fjords excellent systems for developing time series of data for climate impact studies. We provide an overview of the 14 years of data from Norwegian West Coast fjords, focusing on Masfjorden, and report major findings from Oslofjorden in Eastern Norway, exhibiting recurrent hypoxia in the basin waters. We document that the oxygen levels in Masfjorden decreased rapidly by over 60% at 450 m depth in < 8 years, which is much faster than the average rate of deoxygenation in the global ocean. We also discuss the increase in the deep-sea and low-light-adapted coronate jellyfish Periphylla periphylla in view of altered optical conditions of the basin water potentially related to deoxygenation. We argue that fjords like Masfjorden and Oslofjorden are not only macrocosms for ecological processes but also are likely an accelerated version of deep oceans with respect to climate impacts.

Marine fisheries are crucial to the economy, livelihood, food security and culture of coastal nations and communities, significantly contributing to the United Nations Sustainable Development Goals. A decade ago, T. J. Pitcher and W. W. L. Cheung highlighted the dichotomy in the perception of fisheries' status, concluding that long-term sustainability and benefits to people were threatened by overexploitation, climate change, pollution, habitat change and other human stressors. They advocated for a fundamental shift towards ecosystem-based management, better enforcement of existing regulations and more inclusive and equitable management practices. In this paper, we provide an updated review of the status of global fisheries, reflecting on policy actions, key assessments and research findings over the past decade. While there is a growing recognition of the need for sustainable fisheries management and ocean protection, the overall status of fisheries has not improved. Despite progress in international and national policies addressing direct and indirect drivers such as climate change and harmful practices, these trends have not been reversed. Many challenges identified by Pitcher and Cheung and others persist. Additionally, new and emerging issues such as deep-sea mining, plastic pollution, unhealthy aquaculture development, increasing social inequity and the rapidly increasing push for the acceleration of the blue economy exacerbate the complexity of achieving fisheries and other ocean management goals. Debating whether there is more hope or despair in global fisheries has become irrelevant. Pathways to ‘bend the curve’ for fisheries are clear, and effective actions are now urgently needed to achieve desirable and sustainable fisheries.

Species distribution models (SDMs) are critical to the adaptive management of fisheries under climate change. While many approaches projecting marine species range shifts have incorporated the effects of temperature on movement, there is a need to incorporate a wider suite of ecologically relevant predictors as temperature-based SDMs can considerably under- or over-estimate the rate of species responses to climate shocks. As a subarctic ecosystem at the sea ice margin, the Eastern Bering Sea (EBS) is warming faster than much of the global ocean, resulting in the rapid redistribution of key fishery and subsistence resources. To support long-term planning and adaptation, we combine 40 years of scientific surveys with a high-resolution oceanographic model to examine the effects of bottom temperature, oxygen, pH and a regional climate index (the extent of the EBS ‘cold pool’) on range projections through the end of the century. We use multimodel inference to partition uncertainty among earth systems models, climate scenarios and distribution model parameterizations for several ecologically and economically important EBS groundfish and crabs. Covariate choice is the primary source of uncertainty for most species, with models that account for spatial responses to the cold pool performing better and suggesting more extensive northward movements than alternative models. Models suggest declines in the probability of occurrence at low pH and oxygen concentrations for most species. We project shifts that are directionally consistent with, yet larger than those previously estimated for most species, suggesting that accounting for large-scale climate variability in species distribution models may substantially alter range projections.

Ecosystem models predict changes in productivity and status for multiple species, and are important for incorporating climate-linked dynamics in ecosystem-based fisheries management. However, fishery regulations are primarily informed by single-species stock assessment models, which estimate unexplained variation in dynamics (e.g., recruitment, survival, fishery selectivity, etc) using random effects. We review the general benefits of estimating random effects in ecosystem models: (1) better representing biomass cycles and trends for focal species; (2) conditioning interactions upon observed biomass for predators and prey; (3) easier replication of model results using formal estimation rather than informal model “tuning;” and (4) attributing process errors via comparison amongst different models. We then demonstrate these by introducing a new state-space model EcoState (and associated R-package) that extends mass balance dynamics from Ecopath with Ecosim. This model estimates mass balance (Ecopath) and time-dynamics (Ecosim) parameters directly via their fit to time-series data (biomass indices and fisheries catches) while also estimating the magnitude of process errors using RTMB. A real-world application involving Alaska pollock (Gadus chalcogrammus) in the eastern Bering Sea suggests that fluctuations in krill consumption are associated with cycles of increased and decreased pollock production. A self-test simulation experiment confirms that estimating process errors can improve estimates of productivity (growth and mortality) rates. Overall, we show that state-space mass-balance models can be fitted to time-series data (similar to surplus-production stock assessment models), and can attribute time-varying productivity to both bottom-up and top-down drivers including the contribution of individual predator and prey interactions.

The coexistence between offshore wind and fisheries has raised questions about potential impacts on species that are fished. We systematically evaluated the offshore wind farm (OWF) literature for evidence of effects leading to impacts on commercial fisheries species. First, we collated evidence of environmental effects of OWFs on fisheries species and then determined whether these could be interpreted as impacts using fishery-scale and organism-scale parameters for pelagic finfish, demersal and reef-associated roundfish, demersal flatfish, elasmobranchs and shellfish. We appraised consistency and level of agreement of direct evidence and explored the body of indirect evidence. A total of 1268 documents featured evidence of OWF effects on fisheries species, with only 60 documents (274 species records) providing direct evidence. Evidence on finfish far outweighed that for shellfish. Demersal and reef-associated roundfish were the best-studied group, while elasmobranchs were poorly evidenced. Most studies considered population rather than stock parameters. There was limited evidence of impacts, owing to inconclusive results and inconsistent effects within the parameters assessed—illustrating the importance of looking across the evidence base rather than focussing on individual studies. Hence, there is currently insufficient direct evidence to confidently determine OWF impacts on fisheries species. Overwhelmingly, the evidence deals with indirect effects, although these should not be disregarded as they can highlight plausible impacts on fisheries species, which could guide research and monitoring targeted at understanding the impacts of OWF—a pressing concern given the increased policy commitment of many nations to these two marine sectors sharing marine space.