Reviews in Fish Biology and Fisheries最新文献

Small-scale coastal fisheries in the Mediterranean often employ gillnets, a widely used gear worldwide. The disadvantages of gillnets in this fishery include high bycatch levels of unwanted species and consequent discards. Moreover, spatial conflict with other gears and dolphin depredation often results in considerable economic loss. Alternative fishing methods are being tested. This study investigated whether, in small-scale fisheries in the Adriatic Sea, pots can ensure sustainable harvest of mantis shrimp (Squilla mantis), a major target demersal species in terms of landings, and possibly replace traditional gillnets. We adopted a multidisciplinary approach to investigate the catch efficiency, biological impact, and socio-economic effects of the two fishing methods. We found different species compositions in gillnet and pot catches. Gillnets yielded a greater number of discarded species of no commercial value, whereas pots caught a greater amount of mantis shrimp. Finally, a profit analysis indicated that pot fishery has the potential to increase profits for the commercial fishing industry. This study suggests that pots provide a more sustainable fishing method, both in terms of revenue and environmental impact.

Abstract

The incorporation of epigenetics (i.e., change in gene activity without change in DNA sequence) into studies of gene regulation and phenotypic expression has contributed to a significant improvement in our understanding of the evolution of life history traits. One important epigenetic mechanism is DNA methylation, which in vertebrates generally means the addition of a methyl group to a cytosine thus altering gene expression. Here, we discuss progress and gaps in our knowledge of the role of DNA methylation in facilitating diversity across four life history trait classes in fishes: developmental processes, size and growth rates, aging and sexual maturity, and sex regulation. We discuss insights into the regulatory aspect of gene expression in fish which can ultimately influence phenotypic diversity and speciation. We discuss how temperature influences methylation patterns affecting multiple traits. DNA methylation influence on gene expression varies depending on tissue types and the location within the genome of the methylated site (i.e., DNA methylation can increase or decrease gene expression). The role of DNA methyltransferases is also a common denominator across all tissue types in influencing the global methylome status regardless of species or environmental stressor. Organismal development stage is equally important, a decrease in global methylation throughout early development generally corresponds to elevated gene expression associated with growth and development. Finally, we discuss general limitations of DNA methylation studies with a focus on fish. We then provide recommendations for future research.

Graphical abstract

Freshwater eels (Anguillidae) are facing numerous anthropogenic impacts that have led to declines in abundance for nearly all species. They have a complex life history that includes obligate migration and flexible habitat use, characteristics which have generated much research interest in the family. Eels also have high cultural and economic value, further incentivizing the study of key species. We reviewed the scientific literature on anguillids from the last four decades, analyzing research trends among and within species of the genus Anguilla. We identified a shift in research focus from largely biological towards more applied management and conservation topics, an increased emphasis on migration and fish passage considerations, and a tendency towards research on glass eels and silver eels over other life stages. We also identified a significant disparity in research effort between temperate species and tropical species, with a scarcity of knowledge on the latter. Finally, we described several key knowledge gaps about community-based interactions of eels, notably their roles as predator, prey, and ecosystem connector, and highlight opportunities for early career researchers to establish research programs within the field of anguillid research.

Abstract

The Hoplias malabaricus group comprises seven described species, including seven karyomorphs for H. malabaricus. However, the relationship between morphological and chromosomal data within the group remains unresolved. Most studies on the Hoplias malabaricus group from the Iguazu River ecoregion have primarily focused on its upper and middle sections, while the lower Iguazu River remains unstudied. Therefore, in this study, we investigated a population of H. malabaricus from the Capanema’s River (lower Iguazu River basin), Brazil, using cytogenetic techniques and DNA barcode. Through these analyses, we identified the karyomorphs A and D living in sympatry in the lower Iguazu River basin. The karyomorph A, identified as native to the Iguazu River basin, had two cytotypes, designated as A1 and A2, which are differentiated by C-positive heterochromatin and rDNA distribution patterns. Conversely, this is the first record of karyomorph D for the Iguazu River basin, which was previously thought to be endemic to the Upper Paraná River basin and may therefore represent an introduced karyomorph. Interestingly, the cytotype A2 is very similar (same haplogroup) to sequences of Hoplias argentinensis, while the karyomorph D from the lower Iguazu River basin is similar to sequences identified as Hoplias misionera. These findings provided new insights into the diversity of Hoplias gr. malabaricus from the Neotropical region, achieved through cytogenetic and DNA barcode integration. The results also highlight the increased conservation risk for native species in the Iguazu River ecoregion, particularly considering the ecological position occupied by trahiras within the trophic levels.

Graphical abstract

Fish behavior is important to consider when developing selective fishing gear. In studies designed to investigate the size selective properties of towed fishing gears such as trawls, fish behavior is mainly documented by underwater video recordings. Because fishing gear can be operated at great depths or in other low light environments, artificial light is often required for underwater recordings. However, artificial light can influence fish behavior, which casts doubt on the validity of behavioral observations obtained in the presence of artificial light. However, removing artificial light disables video recordings and the possibility to study fish behavior in relation to selectivity devices towed fishing gears in low light environments. To date, little is known about the extent to which artificial light used for video observations affects fish behavior with respect to fishing gear. Therefore, we conducted fishing trials in the Barents Sea demersal trawl fishery to assess the effect of light sources on fish behavior by using size selectivity results in towed fishing gears. We found that the behavior of cod (Gadus morhua) was unaffected by the light sources, whereas the behavior of haddock (Melanogrammus aeglefinus), saithe (Pollachius virens) and redfish (Sebastes spp.) significantly changed when red light and white light were employed. Our results also demonstrated significant differences in fish behavior between white and red light.

Quantifying the trophic role of a species is key to understanding its ecology and ecological role. Their trophic role can influence community composition, ecosystem stability, and nutrient transport and cycling between habitats through ingestion, egestion, and excretion, which requires an understanding of species diet and habitat use. Despite the regular occurrence of sawsharks in Australian temperate fisheries, there remains limited information on their trophic ecology or habitat use, but they are assumed to be benthic consumers. We used fatty acid and stable isotope profiles along with stomach content analysis to investigate the trophic ecology of two sympatric species of sawsharks, the common sawshark (Pristiophorus cirratus) and southern sawshark (Pristiophorus nudipinnis) in south-eastern Australia. Stable isotope analysis of δ¹³C, δ¹⁵N, and δ³⁴S in sawshark muscle revealed that P. nudipinnis fed at a higher trophic level than P. cirratus, and mixing models and stomach contents indicated P. nudipinnis was surprisingly reliant on pelagic and benthopelagic prey sources. In contrast, P. cirratus preyed on more benthic invertebrate species, not found in P. nudipinnis. This bentho-pelagic partitioning between species was supported by P. nudipinnis fatty acid profiles having higher levels of tracers associated with dinoflagellate basal sources (16:1/16:0, 22:6ω3) than P. cirratus, indicating a reliance on pelagic food webs. These data demonstrate that sawsharks are mesopredators that play a substantial role linking pelagic and benthic food webs and highlights the value of incorporating multiple biochemical tracers to provide a comprehensive representation of an animal’s trophic ecology and role in and between ecosystems.

In this study, the four most important species in the Humboldt Current System (HCS), Engraulis ringens, Sardinops sagax, Trachurus murphyi, and Dosidicus gigas were linked to four climate indices, sea surface temperature (SST) and wind speed (WS) based on multivariate statistical analyses, aiming to explore their nonstationary responses to climate variability. Significant decadal variations in the catches were identified, with regime shifts in the mid-1970s, early 1990s, and late 1990s. These shifts corresponded well to climatic and environment regime shifts during these periods. However, the response patterns to climate and environmental variations varied among species. Compared with other physical drivers, seawater temperature, wind speed, the Pacific Decadal Oscillation (PDO), and the North Pacific Gyre Oscillation (NPGO) had greater ecological importance in driving changes in the four pelagic species. The variations in the important climate events influenced seawater temperature and wind speed fluctuations within the HCS, impacting on these commercially important pelagic species. Furthermore, non-stationarity was identified in the relationships between climate/environment and species catches, with different species showing different threshold years. The non-stationarity may be attributed to the transitions between warm and cold periods within the HCS, as well as shifts between strong and weak phases of pressure system. This study helps further understand changes in the HCS caused by fluctuations in climate and environment.

In Namibia, fisheries are important for food security and protein provisioning, income generation and trade; but they are vulnerable to the impacts of climate change. Not only does climate change impact the marine living resources crucial to fisheries; but changes in weather, currents and storminess are affecting the safety and effectiveness of fishing. Here we ask: What are the key risks from climate change to the eight large-scale fishery sectors of Namibia, and for the recreational and small-scale (artisanal) fisheries? For each fishery sector, we assessed three main risk components: (1) climate hazard exposure; (2) fish species sensitivity; and (3) socio-economic vulnerability. In combination, these three risk components are then used to calculate the overall climate risk for each fishery. Climate hazard exposure was assessed as highest for the small-scale, recreational, and rock lobster fisheries. Species sensitivities were highest for the rock lobster and crab fisheries, followed by monkfish trawlers, hake liners and hake trawlers. Socio-economic vulnerability was highest for the small pelagic fishery (linked to the collapse of pilchard). The overall climate risk emerged as greatest for the rock lobster fishery, followed by the (highly marginalised) small-scale artisanal fishery. The key risks by sector emerging from this assessment, informed five stakeholder workshops held across Namibia in 2023, attended by representatives of each sector and aimed at exploring options for climate adaptation. Based on these, we discuss potential adaptation measures that could reduce risk and minimise consequences, in support of improved climate resilience in Namibian fisheries.

Global change has profound effects on marine species, communities, and ecosystems. Among these impacts, small pelagics have emerged as valuable indicators for detecting regime shifts in fish stocks. They exhibit swift responses to changes in ocean variables, including decreased abundances, accelerated juvenile growth rates, early maturation, and reduced adult sizes in warm waters. However, each pelagic species occupies a unique local ecological niche, that reflects the sum of all environmental conditions. Consequently, their responses to environmental changes manifest in distinct ways. We explore here how global change affects small pelagics in the Madeira Archipelago (NE Atlantic Ocean) at (i) community level, by studying the effects of climate change over a 40-year (1980–2019) period on small pelagic landings, and (ii) population level, by studying the effects on the life-history traits of the two most abundant species, Scomber colias and Trachurus picturatus. Our study demonstrated that anomalies in the Sea Surface Temperature and the North Atlantic Oscillation caused a regime shift within the small pelagic community. Both environmental predictors explained 88.9% of the community landings oscillations. S. colias appears to exhibit a relatively more favorable adaptive response to climate change compared to T. picturatus. Understanding the species-specific ecological responses of small pelagic fish to global change is crucial for effective management and conservation efforts in the face of ongoing environmental scenarios.

Graphical abstract

The Chinese sturgeon (Acipenser sinensis) is a critically endangered, large migratory fish that serves as a vital indicator of ecological status of marine and river environments. Conservation efforts for Chinese sturgeon primarily focus on freshwater rearing, potentially leading to smaller adult sizes and higher disease incidence due to limited exposure to marine environments. Thus, it is imperative to study the behavioural characteristics and marine life history of artificially reared populations in seawater environments. In this study, acoustic telemetry technology was employed to investigate the behaviour of the Chinese sturgeon. We deployed an acoustic array at a nearshore-fenced marine farm on Bailong Island and conducted a one-year (December 2020–December 2021) tracking of ten acoustic-tagged fish, comprising five adults and five juveniles. We generated distribution heat maps and analysed displacement during typhoons and tidal events to differentiate activity levels. Annual distribution revealed areas of distinct increased density, with adults displaying a denser distribution compared to the more scattered pattern observed in juveniles. Rhythmic behaviour in response to tidal cycles was observed. During typhoon periods, individuals exhibited reduced activity levels but increased concentration, with no significant diurnal behavioral variations. These age-specific and environmentally responsive habitat preferences provide valuable supplementary insights into the species' life history and potential conservation strategies.

Graphical Abstract