Fish and Fisheries最新文献

Fishes inhabiting the mesopelagic zone of the world's oceans are estimated to account for the majority of the world's fish biomass. They have recently attracted new attention because they are part of the biological carbon pump and have been reconsidered as a contribution to food security. Hence, there is an urgent need to understand how environmental conditions and species interactions shape their assemblages, and how they contribute to the functioning of marine ecosystems. Trait-based approaches are valuable for addressing these types of questions. However, the biology and ecology of mesopelagic fishes are understudied compared to fishes in shallow and epipelagic waters. Here, we synthesise existing knowledge of traits of mesopelagic fishes and relate them to their role in survival, feeding and growth and reproduction, the key functions that contribute to fitness. Vertical migrations, specialised vision and the use of bioluminescence are among the most striking adaptations to the conditions in the mesopelagic realm. Many traits are interrelated as a result of trade-offs, which may help to understand selection pressures. While morphological traits are straightforward to observe, major knowledge gaps exist for traits that require frequent sampling, assessment under experimental conditions or age determination. The unique adaptations of mesopelagic fishes need to be included in management strategies as well as fundamental research of the habitat.

Billions of fishes are kept in captivity for research and food production world-wide, with a strong impetus for maintaining high welfare standards. Accordingly, the importance of empirical research into the welfare and husbandry of captive fishes is increasingly acknowledged in both science and aquaculture, alongside growing public and governmental interest. Physical enrichment can have an important influence on welfare in of captive fishes, but many questions remain. Here, we summarise the current state of research and outline knowledge gaps in the area of physical enrichment, which is a fundamental aspect to improving welfare of captive fishes. To explore the level of research interest this area across time we conducted a series of surveys, using the number of papers published per year as a metric. These surveys highlight that work on fish welfare, while representing a relatively low proportion of fish research overall, is increasing rapidly. For species that are of aquaculture importance or used commonly as laboratory subjects, we show a positive relationship between general research interest and number of welfare-related papers. However, for many, particularly relatively less studied, species the proportion of papers on enrichment remains low, with a slower increase compared to welfare-related papers in general. In terms of common metrics used to quantify fish welfare, there is a reliance on growth and behaviour, with scope for inclusion and combination of a more comprehensive range of reproducible measures. We finish by highlighting recent progress, promising areas for future research and suggestions for advances in this area.

The risk of predation is an important driver that tailors life histories in various ways. Using an evolutionary model based on hormonal control, we study how different predation regimes affect adaptive risk-taking and growth in fish populations. Growth, metabolism and foraging in the modelled fish are regulated by three simplified hormone functions: growth hormone, orexin, and thyroid hormone. A dynamic state-dependent optimization model finds optimal hormone profiles for adaptive growth strategies in juvenile fish. We consider a gradient from species where behaviour and metabolic activity have large consequences for risk (typically benthic and camouflaged species), to the opposite endpoint where behaviour may modify predation risk to a smaller degree (as in the pelagic). Along this gradient, the model predicts changes in the pace of life from slow to fast, enacted by up-regulation of the three hormone functions which in turn increase foraging and metabolism and change the priorities of energy reserves versus growth. Under all types of predation risk investigated, growth is faster when food availability is higher. Energy reserves are maintained primarily during periods of poor food availability and are used to accelerate growth during periods when food availability is high. The thyroid hormone function is up-regulated predominantly when food availability is high and has an important role in trade-offs balancing energetic gain and survival. At the individual time scale, the hormone system improves organismic flexibility and robustness. Over the phylogenetic time scale, hormone system adaptations have also restricted the phenotypic plasticity of individuals.

Several previous studies of marine fish stocks have demonstrated time-varying recruitment productivity and indicated that including time-varying parameters can track process variation in recruitment. Few studies have synthesized signal-to-noise ratios and underlying reasons for time-variation across stocks and regions. Using Peterman's productivity method (PPM), we provide a broad synthesis of time-varying density-independent productivity in 84 stocks across five regions of the United States. Of all stocks investigated, 50 were found to have time-varying productivity, challenging assumptions on the stationarity of recruitment parameters and dependent reference points. Our results demonstrate the power of PPM for synthesizing the form and pattern of recruitment time-variation among regions, including general summaries of directional change over time. Furthermore, our results show regional differences in time-varying patterns, particularly the signal-to-noise ratio (SNR) of low- to high-frequency variation. The SNR was lower in the California Current region than in two Atlantic regions and two Alaska regions. Generalized linear modelling used to synthesize results suggests that stocks with higher contrast in spawning stock biomass over time, standardized regardless of actual spawning stock size, were more likely to have time-varying productivity than stocks with low contrast. The likelihood of time-variation in productivity of a given stock was also found to be closely related to the autocorrelation of the recruitment time series. Such inter-regional and inter-stock comparisons of variation are vital in understanding the roles of local and global environmental change on fish productivity.

Robust estimates of the relative efficacies of alternative management interventions are essential for developing evidence-informed fisheries bycatch policy. Bycatch is a major threat to the conservation of albatrosses and other pelagic seabirds. Branchline weighting is one approach prescribed by regional fisheries management organisations and the Agreement on the Conservation of Albatrosses and Petrels to reduce seabird bycatch in pelagic longline fisheries. We used a Bayesian multilevel network meta-regression modelling approach to conduct the first synthesis of available evidence to assess the relative efficacies at mitigating seabird bycatch of alternative pelagic longline weighting designs. Unlike conventional pairwise meta-analysis, network meta-analysis enables the simultaneous comparison of multiple interventions within a coherent modelling framework. There was a > 97% probability that all weighting designs significantly reduced seabird bycatch compared to a reference design with no weight within 5 m of the hook. Nonetheless, some weighting designs were significantly more effective at reducing seabird bycatch than others—for instance, the 2 designs with weights >60 g and >1 m from the hook performed the best with >93% probability that those 2 designs performed significantly better than 2 more commonly used designs with less weight but attached closer to the hook. These two best performing designs reduced seabird bycatch by ca 89% relative to the reference design. These relative efficacies and rankings, when combined with other performance criteria such as costs to commercial viability and crew safety, support robust evaluations of alternative bycatch management strategies.

Home range size is a fundamental trait that can affect the probability of fish being harvested and, at the same time, may be affected by fishing. The relationship between home range size and fishing will impact the effectiveness of fully protected areas (FPAs), as it will influence the number of fish moving into fished areas, affecting both spillover and edge effects. One hypothesis is that individuals within FPAs will present reduced home range size relative to individuals in fished areas. This pattern can be driven by demographic selection (e.g. fishing of individuals with large home ranges leaving the FPAs), improved habitat requiring less foraging movements, or behavioural changes associated with reduced fishing threats. To test the relationship between home range size and protection, we compiled 1143 individual-level home range sizes based on acoustic tracking, covering 17 species from 11 FPAs in 7 countries, with information on distance from FPA borders. A dichotomic analysis (in/out of FPAs) did not support a significant change in the home range size between FPAs and fished areas. However, continuous analysis across the FPA borders demonstrated reduced home range size within the FPAs. We did not find an effect of FPA age or size on this pattern. While we cannot pinpoint the underlying mechanism for the pattern revealed, we suggest behavioural changes as the main driver for reduced home range within FPAs. This mechanism will lead to more resident populations within FPAs, reducing fishing mortality within FPAs yet limiting spillover benefits to adjacent fisheries.

Tagging fishes with internal or external electronic tracking devices (acoustic, radio, satellite, or archival tags) is invaluable to behavioural, ecological, and welfare research, but may have adverse effects on the animals studied. While short-term responses to tagging (e.g., days to weeks) have often been investigated, less information is available on longer-term impacts (e.g., months to years) and the potential chronic effects of tagging on basic biological needs such as foraging and reproduction. Here, we synthesize existing knowledge from peer-reviewed acoustic, radio, satellite, and archival tagging articles (n = 149) and anecdotal accounts (n = 72) from 36 researchers to assess the effects of tagging over prolonged periods. We identified a dearth of research that has specifically measured or quantified the impacts of tagging over a period longer than a few weeks or months (e.g., median experimental study duration = 33 days; n = 120 articles). Nevertheless, there was limited evidence to support a net negative long-term impact from the implantation or attachment of electronic devices. Considerations and future research directions are discussed with the goal of generating guidance to the research community and minimizing potentially detrimental impacts to study animals. Given the global application and relevance of electronic tagging research to inform conservation and management of fishes, it is imperative for scientists to continue evaluating how tagging procedures affect animal welfare, fate, and the interpretation of tracking data.