Environmental Biology of Fishes最新文献

Bowfin, Amia spp., are broadly distributed freshwater fishes native to eastern North America. Male bowfin build nuptial nests in the spring and provide parental care for eggs and young. Spawning occurs in or near wetland habitats often associated with larger bodies of water, but the literature suggests wider distribution during the growing season, such that annual movements may structure population and community dynamics. However, bowfin movements and their ecological roles are poorly known. Over 3 years, using radio telemetry, we studied movement patterns and home range size of the bowfin, Amia ocellicauda, in Oneida Lake, a large inland lake in New York State. We found female bowfin tended to range more widely than males. Furthermore, within-year structure in movement data and seasonal step-changes in relocations suggest that most bowfin exhibited migration-like movements to and from a primary spawning area in northwest Oneida Lake. After spawning (and for males, after parental care), bowfin dispersed around the western half of the lake, with some fish traversing the full extent of our study area. Analysis of home range sizes revealed high variability in how widely individuals roamed, but there was a significant tendency for females to exhibit larger home ranges than males during the spring. During the summer, there was a tendency for individual bowfin of both sexes to inhabit the same area in successive years, though males appeared to exhibit site fidelity more often than females. These data provide a new perspective on the movement ecology of bowfin.

Hardhead catfish (Ariopsis felis) are one of two Ariidae catfishes in the northern Gulf of Mexico and are one of the most common fishes found in the coastal waters in this region. As a generalist consumer with a unique reproductive life history and limited information on long-term population dynamics in the Western Gulf of Mexico, the objectives of this study were to assess trends in Texas estuaries using long-term fishery independent and dependent data sets and to conduct habitat suitability analyses in these same estuaries for both young-of-the-year and adult hardhead catfish. Some estuaries have experienced decreasing trends in catch-per-unit-effort (CPUE) of adult hardhead catfish beginning in the mid-1990s and early 2000s, and widespread decreasing trends in adult mean length were additionally observed for central and lower coast estuaries. Compared to the CPUE of finfish in the larger community, adult hardhead catfish largely exhibited decreasing trends in their relative contribution (expressed as percentage of CPUE) across most Texas estuaries. When combined with the larger Ariidae species grouping, and compared to the relative contribution of common Sciaenids, it was generally observed that the contributions of these two species groupings were converging for many estuaries. This was primarily characterized by increasing Ariidae trends. Given the trophic role of Ariidae catfishes, they clearly have the potential to exert major trophic influence on estuarine food webs. Our study highlights the value of long-term monitoring and the study of non-gamefish species in the larger assessment of community change across time.

Marine protected areas (MPAs) are common conservation tools supporting the protection of threatened marine fishes, such as sharks. However, the creation of shark MPAs has been less common in the Greater Caribbean region despite a growing need and opportunity. In this study, we evaluated the occurrence of shark and reef fish biodiversity off Sint Maarten, Dutch Caribbean, with a particular emphasis on endangered shark presence within the Man of War Shoal Marine Protected Area (MPA). We utilized baited remote underwater video systems (BRUVs) to gather non-invasive data on the abundance and diversity of reef fish and shark species inside and outside the local MPA. Generalized linear models (GLMs) revealed no significant effect of protection status on the presence of the endangered Caribbean reef shark (Carcharhinus perezi). However, we found a significant influence of depth on shark occurrence, as well as an effect of habitat type on shark and reef fish biodiversity, with reef habitats showing the greatest significance. These results suggest that the effect of small coastal MPAs on bolstering local endangered species conservation in the Dutch Caribbean is likely to vary according to habitat features and how those species utilize those habitats across various life stages. These findings have implications for adaptive MPA management, which should be informed by the ecology and habitat preferences of target species to achieve maximum benefits for biodiversity conservation.

In this study, we aimed to identify the factors that drive the patterns in beta diversity of fish assemblages on the beaches of the Volta Grande do Xingu, a river stretch under the influence of Belo Monte dam. Fishes were collected using a trawl net in 28 sandy beaches during the low water period of 2021 (each beach was sampled once during this period). Measurements of environmental variables were carried out on-site, while spatial variables were obtained using Asymmetric Eigenvector Maps (AEM). Using the Bray–Curtis dissimilarity index, we calculated beta diversity and conducted a distance-based redundancy analysis (db-RDA) with the dissimilarity matrix to assess its relationship between beta diversity and environmental and spatial variables. Additionally, we performed a variance partition to quantify the pure and shared contributions of the explanatory matrices to our response matrix. The results revealed low beta diversity among the sampled beaches, and that this beta diversity was explained in part by the spatial variables and pH. Our findings underscore the influence of spatial structure on the assembly of local communities, indicating that dispersion processes and spatial connectivity are relevant mechanisms that contribute to the beta diversity of beach fish communities under influence of a reduced flow by a Hydropower Plant.

Lake Erie supports many native nongame fishes including freshwater drum, bigmouth buffalo, and smallmouth buffalo. Commercial fisheries in Ohio waters of Lake Erie have no specific regulations on these species. We reviewed the commercial harvest records for these species and quantified population characteristics (size structure, age and growth, length and age at maturity, recruitment variability, and mortality rates) with fishery-independent samples. Commercial harvest effort has generally declined through time, but commercial harvest totals have increased, suggesting potential increases in population size. Sexually dimorphic growth occurred for each species, with females attaining larger sizes than males. Total annual mortality was 6.7–12.2% and recruitment variability indexes ranged from 0.44 to 0.51. Most fish of all species matured by age 6 or 7, and maximum observed ages were 56 years for freshwater drum and 48 years for buffalo species. A catch-only surplus production model suggested overharvest of freshwater drum, and buffalo species has occurred in the past and is likely ongoing. However, these results disagree with biological information collected on the fishery (i.e., age structure, growth, and recruitment). We suggest it is likely some level of overharvest is currently occurring in this fishery; however, more detailed assessment of harvest (i.e., information about size structure rather than aggregate total biomass removed) should be conducted to ensure it can be sustainably managed.

In applied research, there is an expectation that knowledge generators will produce information that can be acted upon by knowledge end users (i.e., actionable knowledge); however, this is not always the case, resulting in a knowledge-action gap. Currently, there is no literature directly targeted at fisheries knowledge generators (e.g., researchers) to guide them in producing knowledge that could be readily used to inform fisheries management and conservation. To that end, this paper provides evidence-based recommendations for researchers to produce actionable knowledge. Key recommendations include the following: (1) embrace co-production; (2) prioritize capacity building; (3) include Indigenous and local knowledge systems; (4) diversify forms of knowledge exchange; (5) participate in interdisciplinary research; and (6) provide training for early-career researchers on producing actionable knowledge. We also analyze challenges to producing actionable knowledge, such as trust imbalances, costs of engaging in highly collaborative work, and difficulties related to effective knowledge exchange with fast-moving research timeframes, funding restrictions, and lack of institutional support. Using several case studies, we examine how knowledge generators overcome such challenges to successfully implement the key recommendations. It is our hope these recommendations will encourage and facilitate actionable research, contributing to more effective fisheries management and conservation.

Sander lucioperca represents a potential candidate for aquaculture in Moroccan freshwater, but information concerning its diet and feeding habits is still lacking. This study therefore aims to contribute to the knowledge of the feeding ecology of this invasive species in Al Massira Reservoir, with particular emphasis on seasonal and intraspecific diet variation. Analysis of stomach contents revealed that the pike perch diet consists of various prey items, with an abundance of Lepomis gibbosus. However, S. lucioperca is also an opportunistic predator, capable of consuming other food resources when they become available in its habitat. This opportunistic behavior may account for the successful establishment of this species' population in a large reservoir, despite the coexistence of other carnivorous fish species. The dietary composition indicated a carnivorous diet with considerable seasonal variation. There was no significant sex-related or ontogenetic variation in the diet. The feeding intensity is similar between males and females, as well as across different size classes, but it varies according to the seasons. The results provide fundamental information about the feeding habits of this species, which is used for artificial culture research.

The Atlantic bigeye Priacanthus arenatus is among the main target species by small-scale fisheries in the southwestern Atlantic. Due to its importance to small-scale fisheries, information regarding its trophic ecology is essential for the development of sustainable management plans. Using combined stomach content (SCA) and stable isotope analysis (SIA), the current study examined Atlantic bigeye feeding ecology, including evidence for ontogenetic and intra-annual (i.e. seasonal) diet variation. The diet of Atlantic bigeye was comprised of 16 prey species but was dominated by pelagic crustaceans (53.3% in number) and pelagic fish (19.7%), and benthic crustaceans (11.0%). SCA identified diet variation among seasons (higher dissimilarity in Spring vs. Autumn), which is most likely related to the occurrence of intense coastal upwellings. Significant positive relationships between fish size and δ¹⁵N and δ¹³C values indicated an ontogenetic diet and potential habitat shift; broad isotopic niche area in small individuals (size class I: 115–169 mm) narrowed with increasing body size with the highest niche overlap occurring between size class II (170 to 243 mm) and class III (244 to 308 mm). Overall, the combined SCA and SIA approach determined that the Atlantic bigeye’s diet is closely connected to the pelagic food web. These data provide an improved understanding of ontogenetic and seasonal variation in Atlantic bigeye predator-prey interactions in the southwestern Atlantic.

Mobulid rays are among the most vulnerable of chondrichthyans to overexploitation by fisheries due to their low population growth rates. In locations where catch data are lacking, long-term sightings data can provide valuable insight to infer population trends and status. We recorded underwater sighting data of reef manta rays (Mobula alfredi), oceanic manta rays (M. birostris), and shorthorned pygmy devil rays (M. kuhlii) between 2003 and 2023 in the waters off Praia do Tofo in the Inhambane Province, southern Mozambique, one of the major global hotspots for these rays. We modelled sightings data using a hierarchical generalised linear mixed model framework to account for a suite of environmental variables when examining temporal trends. Raw trend models including only ‘year’ as a predictor showed a 99% decline in sightings of reef manta rays, a 92.5% decline in oceanic manta ray sightings, and an 81.3% decline in devil ray sightings over the 20-year study period. The declining trends persisted for reef and oceanic manta rays once a suite of temporal and environmental variables were accounted for, indicating that the declines were driven by external factors not tested in the models. For shorthorned pygmy devil rays, models that incorporated environmental variables did not retain year as a significant predictor and showed a reduced overall decline in sightings of 36.5%. This indicates that the tested predictors were responsible for approximately half of the observed decline. Anthropogenic factors, particularly fisheries mortality, are likely to have played a significant role in the declining sightings of these three Threatened species. Improved conservation and management measures at a national and international level are critical to prevent further declines, which may otherwise lead to localised extinction.

Estimation of population dynamic rates is one of the most established and widely recognized components of modern fisheries management, yet this information is rarely collected for non-threatened native species. Pejorative views of native, underrepresented fish have contributed to a dearth of research and management efforts for these species. We sought to reduce this knowledge gap for one of the most widely distributed freshwater fish in North America, Freshwater Drum Aplodinotus grunniens (Rafinesque, 1819). We calculated estimates of growth, mortality, and recruitment from lotic environments in the most northern drainage of their range (i.e., Hudson Bay). Our estimates of growth (K, Brody growth coefficient) are similar to studies as far south as Alabama, USA. Estimates of annual mortality (4–10%) and longevity (62 years) are consistent with latitudinal trends observed in the standing literature. We found evidence of recruitment variability (recruitment variability index = 0.53), with a positive association between growing season degree days and year-class strength. Hydrologic variables of discharge during the cold season and rise rate were found to have negative relationships to recruitment. This research gives insight into factors regulating Freshwater Drum populations and will provide useful information for the management and conservation of this widespread but underappreciated species.