Ecology of Freshwater Fish最新文献

Climate change projections predict warmer temperatures and increased frequency of heat waves in many regions across the globe. These scenarios are expected to strongly impact temperature-dependent life-history traits of aquatic species, such as the embryonic stage of annual fishes inhabiting temporary freshwater wetlands. Here, we assessed the effects of different incubation temperatures (18, 24, 27 and 30°C) and exposure to heat waves (18–30°C for 6 h) on aspects of the embryonic development: mortality and trajectory (direct development or diapause entry) of two Neotropical species of annual fishes from high- (Austrolebias nubium) and low-altitude (A. cyaneus) areas. Temperatures of 30°C resulted in 100% embryo mortality in both species, and development trajectory differed between species across temperatures. Embryo mortality in the high-altitude species was higher at 27°C, while a higher number of embryos of the low-altitude species entered diapause II at 18°C. Embryo mortality and development trajectory after exposure to heat waves were similar between species. In terms of implications for climate change scenarios, temperatures above 27°C seem critical for the embryo survival of both species studied, although they seem capable to endure short-term events of heat waves. In summary, our results indicate that the persistence of populations of high-altitude annual fish species may be subject to higher threat under warming scenarios, since embryos from this species were more sensitive to increasing temperatures than the low-altitude species.

We investigated the relative influence of local environmental and spatial factors in structuring the community composition of fish at 15 sampling sites along the longitudinal gradient of the Lower Niger River Basin (LNRB) in dry and rainy seasons using distance-based redundancy analysis and variation partitioning analysis. We collected a total of 3807 fish specimens representing 42 species. Our result indicated that the fish community composition differed between the upper and lower regions of the river. The communities in the upper region is influenced by high-nutrient concentrations, while downstream sites were characterized by high concentrations of suspended solids. Variation partitioning revealed higher contributions of spatial than environmental predictors on fish community composition, with a higher total predicted variance in dry season. The variations in the community composition between upper and lower region may be attributable to the differences in the nature of anthropogenic activities within the regions, which influenced the local conditions differently. Differences in flow dynamics between upper and lower regions as attributable to black and white floods in the LNRB modify the connectivity between sites. Dispersal among sites may be more limited downstream than in the upper region, particularly in the dry season, because damming in the upper region also interrupts the natural flood regime such that there are low water levels in the lower region, which spatially isolate fish communities at certain sampling sites. The relatively higher total predicted variance during dry season may be attributable to the temporal differences in abiotic conditions between sites, which may have influenced site level community composition and abundance differently.

Lakes provide important habitat for salmonids that may use them as a primary feeding area between periods of reproduction. The seasonal changes in vertical thermal structure in lakes can affect the distribution of salmonids on seasonal and diel time scales as they search for, consume, and digest prey that also exploits the water column's distribution of food, temperature and light. Our goal was to analyse the vertical distribution of wild, native coastal cutthroat trout (Oncorhynchus clarkii clarkii) in Lake Washington on daily and seasonal time scales. This lake is stratified in the summer and isothermal in winter, allowing us to compare vertical movements between periods with and without thermal structure in water 50 m deep. We predicted that trout would be deeper in the water column during stratified months and shallower during isothermal months, and shallower at night than in the day. Overall, the trout showed these patterns in the depths and temperatures they occupied, tending to be within or below the thermocline in the summer but not in the coolest water available, and closer to the surface when the lake was isothermal. The trout were also closer to the surface at night and deeper during the day. The vertical range of these diel movements shifted with the seasons–deepest in October, as the thermocline deepened and weakened, and shallowest in January when the lake was isothermal. These seasonal and diel vertical distribution patterns by the trout optimise metabolism for growth, and facilitate feeding on planktivorous fishes that also show seasonal and diel vertical distribution changes.

In large river floodplains, the availability of trophic resources to the fish fauna is highly variable as a consequence of seasonal environmental change and habitat diversity. Young-of-the-year fishes (YOY) must find suitable habitats to settle, feed and survive. However, very few in-depth studies are available about the food preferences of the young fishes during their first growing season. Here, we investigated the composition of planktonic assemblages and the YOY diet of three generalist fish species Alburnus alburnus (Linnaeus, 1758), Squalius cephalus (Linnaeus, 1758) and Pseudorasbora parva (Temminck & Schlegel, 1846) from four floodplain sites of the French Upper Rhône River. More specifically, we studied their temporal and spatial variations in relation to five environmental variables: hydrology, dissolved oxygen, primary production, water temperature and conductivity. Stable flow conditions and the associated temperature and conductivity strongly structured the phytoplankton community in the floodplain channels, whereas water movements within channels and dissolved oxygen concentrations were significantly correlated to the zooplankton composition. A zooplankton density above ≈100 ind L⁻¹ allowed the initiation of a YOY diet mainly based upon zooplankton for the three fish species. When zooplankton densities were insufficient, all three species used phytoplankton as their main food resource. Finally, the diet overlaps between species, differed significantly between sites. The study highlights the need to examine the diet of juvenile fishes and environmental variables in the floodplains.

This study aimed to explore the relative importance of mesohabitat and microhabitat features, as well as the spatial and within-day temporal covariates, on the body size-related within-reach spatial distribution of stream-dwelling fishes in a highland-type and a sub-mountainous-type stream in Central Europe. During daytime, point abundance sampling was applied to catch the fish, and environmental data were recorded at the sampling points (microhabitat features) and along the transects that crossed the sampling points (mesohabitat features). Variance partitioning revealed similar patterns in the size-classified fish data for the two streams. Microhabitat features had a greater explained variance than mesohabitat features. The majority of the mesohabitat influence emerged as variance shared with the microhabitat influence. The pure spatially explained variance proportion was lower than the variance explained purely by the environmental features (meso and micro together), and no temporally explained variance was found. Many species showed body size-related environmental associations. The results suggest that the different-scale habitat features act in a hierarchical way on the within-reach fish distribution. Meso-scale features may determine a great proportion of the micro-scale habitat variability and micro-scale conditions may directly affect how fish select places to stay as a function of both species identity and body size. The restoration of meso-scale environmental diversity can effectively contribute to the protection of size-structured populations in sub-mountainous and highland streams.

The Baltic Sea has been under intense environmental changes in the recent decades, such as climate change, eutrophication and increasing abundance of top-predators, which pose serious challenges to its aquatic life. For informed conservation measures and sustainable yields, we need to understand how the populations are being affected. Accordingly, we used long-term data series (covering the period between 1980 and 2021) to assess how these changes have affected populations of an ecologically and economically important predatory fish, the pikeperch (Sander lucioperca), in the coastal waters of Finland in the northern Baltic Sea. We investigated the estimates of abundance and recruitment, commercial and recreational catch statistics and growth and mortality rates. We found a clear increase in the total catches in the northernmost part of the Finnish coast (Bothnian Bay) that were not explained by changes in fishing effort, indicating increased abundance, most likely due to higher water temperature. In the southern part of the study area (Archipelago Sea), density-dependent factors prevented the development of particularly strong year classes, despite the beneficial conditions of warming seawater and consecutive warm summers. Individual growth has increased in younger age groups, contributing to an upward trend in the spawning population biomass. We also uncovered a declining trend in the total mortality in the southern area, despite increased abundances of cormorants and seals, explained by reduced total fishing mortality. These results show that the pikeperch is one of the species that has, thus far, benefited from the environmental change in the northern Baltic Sea, strengthening its role in the ecosystem.

Endoparasites that are trophically transmitted are closely intertwined and constrained by the structure of the food chain. Each fish species can be used as an intermediate or definitive host; thus, the position it occupies in the food web and the body size can be determining factors for the presence of parasites and their transmission. Considering that fish can be parasitized by larval and adult stage endoparasites and that they are exposed to a wide variety of parasite species, we used a helminth dataset from 70 fish species and tested whether the total parasite richness, larval and adult, of fish from the upper Paraná River floodplain can be explained by body size and trophic level. For the trophic level, we observed an increasing trend in the richness of larval parasites. Regarding the richness of adult parasites and the total richness, we observed an increase as a function of the body size of the host. The tropic position and body size of the fish were good predictors, indicating that the position of the host in the trophic chain can influence and determine its life cycle.

Bythotrephes longimanus is a predatory zooplankton native to Eurasia known for its large caudal spine. This species can decrease Daphnia abundance and may decrease growth rates of native planktivorous fish including yellow perch (Perca flavescens). Bythotrephes was first documented in Oneida Lake, USA in 2019 and reached high densities in 2020 and 2021. This recent invasion created an opportunity to investigate at what length yellow perch feed on Bythotrephes, if age-0 yellow perch select for Bythotrephes, and if yellow perch first-year growth decreased. We found Bythotrephes in the stomachs of 23% (2020) and 35% (2021) of age-1 and older yellow perch caught from June through September and 54% of the age-0 yellow perch caught from June through October (2021). Age-0 yellow perch started feeding on Bythotrephes at 27 mm and selected for Bythotrephes from June 24 through the autumn of 2021. Bythotrephes accounted for 54% of age-0 diets by dry weight over the summer and fall. We used the extensive water quality and biological monitoring data from Oneida Lake to develop a multivariate linear regression model for age-0 yellow perch October length from 1993 to 2021. Significant variables included were age-0 yellow perch abundance (negative effect) and temperature, Daphnia biomass, and Bythotrephes presence, all positive effects. Contrary to our expectations, Bythotrephes were selected by age-0 yellow perch from end of June through October, and contributed a substantial proportion of ingested mass by age-0 perch, without negatively affecting age-0 yellow perch growth.

Understanding the processes governing population dynamics is important for effective conservation and environmental management. Disentangling the relative role of density-dependent versus density-independent processes on population dynamics is often made difficult by the inability to control for abiotic or biotic factors, but long-term datasets are invaluable in this pursuit. We used a 14-year dataset from the Logan River, Utah, to assess long-term trends in abundance and evidence of density-dependent and density-independent effects on population dynamics of Paiute sculpin (Cottus beldingii) across six sites. Additionally, we evaluated the feeding ecology of sculpin over 4 years. Sculpin densities generally increased from upstream to downstream, and the annual per capita rate of increase was negatively and significantly correlated with sculpin density at four of six sites. We observed a negative relationship between total gut content and sculpin density but did not observe a negative relationship between relative condition and density. Sculpin displayed a generalist feeding strategy, and interannual differences in diet composition appeared to be influenced by interannual differences in flow, particularly years with higher magnitude flow. The observed spatial patterns in sculpin abundance throughout the watershed matched those of invasive brown trout (Salmo trutta), the top piscivore in the Logan River, and likely represent affinities for the suite of ecological conditions associated with downstream sections of the Logan River. Our results suggest that sculpin populations are regulated largely by density-dependent processes and match those from other studies on sculpin population dynamics including a range of species and habitats that differ vastly in abiotic conditions.