Ecology of Freshwater Fish最新文献

The diel distribution of early juvenile fish communities from two temperate freshwater reservoirs that differed in cover of submerged aquatic vegetation was investigated. In the daytime, about 99.9% of the juvenile fish community from the plant-rich Žlutice Reservoir was found in the nearshore belt of submerged aquatic vegetation reaching an average abundance of ~7982 inds. 1000 m⁻³. In contrast, in the pelagic habitat, few fish were found at day. In the plant-poor Římov Reservoir, 98.9% of juveniles occupied the pelagic habitat during daytime and reached an average abundance of ~333 inds. 1000 m⁻³. Vertical distribution of fish in the pelagic habitat in both water bodies was affected by steep thermal and oxygen stratification and no individuals occurred below 6 m depth. At night, 88.8% of the juvenile fish community from the plant-rich Žlutice Reservoir was in the pelagic habitat with an average abundance of ~1423 inds. 1000 m⁻³. Their diel horizontal shifts were much more pronounced compared to the community from the Římov Reservoir that reached an average nighttime pelagic abundance of ~523 inds. 1000 m⁻³. Only 1.1% of the juvenile fish community in the Římov Reservoir was found in the littoral during the daytime and 0.7% at night reaching an average daytime abundance of ~1688 inds. 1000 m⁻³ and average nighttime time abundance of ~1664 inds. 1000 m⁻³. This study indicates that if a well-developed littoral zone with abundant aquatic vegetation is present, early juvenile fish will perform diel horizontal movement in temperate stratified reservoirs.

An active preference for higher temperatures within a physiological optimum is beneficial for animal movement. For example, ascending temperatures induce an increase in cyprinid fish metabolism and swimming ability. Spring upstream migrations driven by the search for resources may be related to these increases. Conversely, downstream migrations in autumn follow a decrease in temperature. When fish migrations are driven by a search for resources, for example, food availability and reproduction, or to avoid predators, then the temperature effect can be reduced to approximately the threshold temperatures that induce up- and/or downstream movement. To test this assumption, we tracked the seasonal migrations of the common bream Abramis brama between a reservoir and its tributary using radio tags with temperature sensors during a 5-year period. Upstream migrations of the species into the tributary were not motivated by seeking temperatures different from those in the reservoir, that is, fish body temperatures in both environments were comparable across seasons. However, for long-distance migrations, increasing temperature did support upstream migrations. Temperature did not determine the direction or intensity of short-distance migration of the species between the reservoir and the tributary. No significant influence of temperature was recorded for the downstream migrations according to the results of the generalised additive mixed model (GAMM1), which related movement distance as the explanatory variable to the signed fish body temperature as the response. The second model (GAMM2) relating fish body temperature as the explanatory variable to the signed movement distance as the response obtained a threshold value of 19.1°C for the upstream migrations and 1.5°C for the downstream migrations of the common bream.

The trophic niche of aquatic generalist predators is influenced by ontogeny, habitat characteristics, availability and type of prey, and competitive interactions. Many interrelated lake characteristics influence the availability of prey and may thereby impact foraging niches and the trajectory of ontogenetic niche shifts. Our work uses Eurasian perch (Perca fluviatilis) as a model species to examine the correlation of multiple lake and fish community characteristics with the size-dependency of perch populations' realised trophic niche. We used carbon and nitrogen stable isotopes to correlate the changes in perch trophic position across a gradient of total lengths in seven gravel pit lakes that differed in lake morphology, habitat heterogeneity, productivity, structural complexity, and fish community composition. Perch populations in lakes with more shallow-water habitat reached a higher trophic position at smaller sizes than perch in deeper lakes. However, the changes in trophic position with increasing size were less pronounced compared to perch from deeper lakes. Large individuals from the latter perch populations ultimately achieved higher mean trophic positions compared to fish from shallow lakes. Perch in lakes with more shallow-water habitat may, therefore, achieve lower rates of piscivory because of higher relative availability of macroinvertebrates or greater competition with zooplanktivores. Our results suggest that large, piscivorous perch are more likely to develop in deeper lakes, and that these changes in perch trophic position across ontogeny are more strongly related to the depth of lakes than to the type of structured habitat in the littoral zone.

Lake Erie walleye (Stizostedion vitreum) recruitment fluctuates annually and depends partially on their diet and growth during their first year of life. In recent decades, age-0 walleye diet and growth may be responding to food web changes in western Lake Erie. To determine how age-0 walleye have responded to changes in prey species and abundance, we compared diet between 2019, 2014 and 1994–1999. Larval walleye ate predominantly cyclopoids in 2019, compared to 1994–1999 when calanoids were the most consumed copepod. Juvenile walleye ate predominantly large cladocerans and benthic invertebrates in 2019, compared to 2014 and 1994 when fish was the most consumed prey. Additionally, in 2019 and 2014, age-0 walleye ate two of the current aquatic invasive species (AIS), Bythotrephes longimanus and Neogobius melanostomus, and the historical AIS, Osmerus mordax. Age-0 walleye were smaller in 2019 than in 2014 and switched to consuming more AIS and less fish suggesting that more energetically favourable prey were not available. While age-0 walleye showed adaptation to new prey and conditions, they had a lower quality diet because they consumed less fish, but also because the invasive fish they now consume have a lower energy density than native species. However, lower quality diet and size may not result in reduced survival, if adequate alternative prey is available. Continued monitoring of age-0 walleye diet could provide confirmation that lower diet quality during the first year decreased walleye growth and aid to identify any effects changes in age-0 diets has on recruitment to the adult population.

Freshwater fish metacommunities are best understood when considering the dendritic structure of riverine networks. The dendritic structure imposes restrictions to dispersal associated with the connectivity. Many structures restrict the movement of fish even more, such as dams and the terrain slope (dispersal costs). We investigated the influence of environmental predictors and dispersal costs on the beta diversity of freshwater fishes from the Upper Tennessee River using Generalised Dissimilarity Modelling (GDM). In addition, we tested the effects of asymmetrical dispersal costs (high costs for upstream dispersal) on the nestedness of native and non-native fishes. Environmental predictors were more important than dispersal costs for explaining the overall fish dissimilarity in the GDM models, with the turnover capturing most of the explanation compared to the species richness difference. Dam heights were the most important dispersal cost variable in the GDM, mainly for species turnover. Overall dissimilarity of the native fish subset was better explained by environmental and dispersal variables than non-native fish (20.03% vs. 8.41%). Considering the native species assemblage subset, dispersal cost related to maximum channel slope between pairs of sites and watercourse distance increased the nestedness of adjacent upstream–downstream sites, whereas those attributed to dams reduced the nestedness. The results support that dams increase overall dissimilarity in the native fish metacommunity of the Upper Tennessee basin, but also reduce the nestedness of adjacent sites. Our findings improve the knowledge on how mechanisms and processes associated with dispersal costs in watersheds under the effects of dams create patterns of dissimilarity and nestedness.

Non-native fish species may generate major ecological impacts on native assemblages. This study aims to assess the potential impact of the introduced Arapaima gigas on native fish assemblages in two oxbow lakes of the Bolivian Amazon. Stable isotope data were used to determine trophic position (TP) and isotopic niche overlap, to evaluate potential predation and competition interactions, respectively. Results suggest that A. gigas is more an omnivore than a top predator, as often claimed. Arapaima gigas occupied an intermediate TP between detritivore/herbivore and piscivore fish species and showed broader isotopic niche compared to most native species analysed. The isotopic niche of A. gigas significantly overlapped with most native fish species in one lake (i.e. Lake Mentiroso), while there was low niche overlap in the second (i.e. Lake Miraflores). Given its omnivorous tendencies, the predation impact of A. gigas on other fish species is likely less than currently claimed and likely varies with the food web structure of the ecosystem. More precise data on resource availability and use are necessary to infer whether niche overlap will have negative impacts on native fish species through potential competitive interactions. Increasing our understanding on the processes generating impact of these introductions on resident communities through food web ecology will pave the way for better resource management and conservation efforts.

Initial investigations of home range for freshwater fish noted that it scaled allometrically, with additional studies having linked home range to variations in water body size. Here, we revisit the analysis of factors influencing freshwater fish home range sizes using an expanded dataset incorporating more recent telemetry data and a meta-analysis approach to evaluate the influence of fish length, water body size, trophic guild and latitude on the home range size of fishes in lotic and lentic systems. With the expanded data set we reaffirm that length has a significant effect on the home range size in both lentic and lotic environments, with the effect of length being more pronounced in lotic environments. Similarly, we determined water body size also significantly influences home range size and is the key determinant of home range size in both lentic and lotic environments. We also demonstrate the importance of trophic guild and latitude as determinants of home range in lentic and lotic environments. The factors influencing home range size in both environments were common (i.e. fish length, water body size, trophic guild and latitude), but varied in importance weight between the environments. The results of this study help illuminate the weight of importance of factors influencing the home range of freshwater fishes and provide useful information for conservation and environmental management planning purposes.

Abundance, placement beneath cover and clustering of brown trout spawning redds were monitored throughout five spawning seasons (2016–2020) in a 4.8-km reach of a Minnesota coldwater stream to assess the potential impacts of concurrent stream habitat rehabilitation projects. We anticipated that redd abundance (redds/100 m stream segments) and placement beneath cover (e.g. logs and branches, boulders, overhanging bank vegetation, aquatic macrophytes) would increase and redd clustering (placement within 1.5 m of other redds) would decline as stream sections were rehabilitated. Repeated redd counts were conducted for the entire stream reach during each of the five spawning seasons, and redd cover and clustering were documented. Before-after comparison of impact (BACI) tests were used to compare redd abundances in control versus rehabilitated stream sections, and before-after distributional tests compared redd placement beneath cover and redd clustering within rehabilitated sections. In total, 1895 brown trout spawning redds were documented within the study reach during the five spawning seasons combined. Redd abundance increased nearly fivefold throughout the 5-year study period (from 3.5 to 15.5 redds/100 m), but no significant difference was detected in redd abundances between rehabilitated versus control stream sections. Redd placement beneath cover (63% beneath cover in total) also increased throughout the study, but at a rate nine to 45 times greater in stream sections rehabilitated during the study than in control or previously rehabilitated sections. Redd clustering remained unchanged (5-year means = 35 to 46% of all redds clustered) in rehabilitated sections, but increased significantly through time (0% to 35%) in the control section. Stream habitat rehabilitation did not increase spawning redd abundance or reduce redd clustering in rehabilitated stream sections, but redd placement beneath cover increased after rehabilitation to levels present in other stream sections.

Ecosystem services provided by communities are related to the diversity of functional traits, and biotic functional simplification occurs when this diversity is reduced. Thus, we used the approach of functional indices, applied to the abundance of fish larvae and traits of the spawning stock, to evaluate the spatial and temporal variations in the functional diversity of the fish community of a Neotropical reservoir. The following hypotheses were tested: (i) different environmental conditions between reproductive periods lead to temporal variations in the functional diversity of the community, and (ii) the spatial heterogeneity (longitudinal and lateral) of the environmental conditions formed in the reservoir causes functional biotic simplification to occur from lotic towards lentic areas since the original community was formed by rheophilic species. Larval collections were carried out monthly, at night, between October and March, from 2009 to 2016, with plankton nets equipped with a flowmeter in nine sample areas categorised into three longitudinal zones (fluvial-FLU, transition-TRA and lacustrine-LAC) and three sides (upper-UPP, middle-MID and lower-LOW). Water samples were obtained to measure the temperature and turbidity. Precipitation and reservoir quotas were obtained from official agencies. After the identification of captured larvae, we determined which species were present and used the functional traits of the adults (parental stock), obtained from specialised literature, and functional richness (FRic) and its corresponding standardised effect size (SES.FRic) were computed. The spatiotemporal variations in these indices were evaluated through the two-way block factorial MANOVA/ANOVA. Their association with environmental variables was inferred through multiple linear regression models. Altogether, 51,995 larvae were captured with the highest abundance in the period V, longitudinally in LAC and TRA and laterally in LOW. Among these, the functional indices were higher in periods IV and V. The highest values of FRic occurred longitudinally in FLU and laterally in LOW. Among the abiotic conditions, rainfall and water temperature were the most influential variables over functional indices and total larvae abundance. The results indicate that fish reproduction is linked to spatiotemporal variations in abiotic conditions confirming our first hypothesis. The second hypothesis was partially supported because functional biotic simplification was observed in the longitudinal gradient, with reductions in FRic in LAC. However, this reduction was not observed in the lateral gradient. We showed that the temporal variability of abiotic conditions is important for the high functional diversity of reservoirs.