Ecology of Freshwater Fish最新文献

The round goby (Neogobius melanostomus) is an example of an invasive species where the adults are unimpressive swimmers and yet via human activities, they have managed to rapidly invade the Laurentian Great Lakes, the Baltic Sea and many rivers in Western Europe. The secondary spread from human-impacted sites has been attributed to adult life stages, despite their poor swimming capacity. However, the swimming capacity of early life stages of round goby has not been considered before. We therefore quantified critical swimming performance (U_crit), sprint swimming performance (U_sprint), burst swimming speeds and swimming behaviours in early juvenile round goby that ranged between 10 and 25 mm in body length. The average U_crit, U_sprint and burst speeds of these fish were an impressive 0.22, 0.34 and 0.67 m/s respectively, with the capacity of these early juveniles ranging between 41 and 79% of what has been documented for adults. Notably, fish spent more time actively swimming as current speed increased, while station holding decreased. Taken together, our findings highlight that despite their small size, early juvenile round goby are not simply passively moved by currents but have movement capacities that approach that of the much larger adults. Our study emphasizes the need to consider the swimming capacity of all life stages as this information will better predict dispersal and range expansion and will help to design mitigation efforts to potentially prevent the spread of this and other invasive species.

In order to investigate the reproductive dynamics of the ichthyofauna in the Brazilian Pantanal, this study examines the spatial and temporal distribution of ichthyoplankton, taxonomic composition, and its correlation with environmental factors within one of the most important sub-basins, the Taquari River. Egg and larvae collections were conducted at 11 sampling points between October and March of 2017/2018 and 2018/2019. Significant differences were observed between collection points, months, and years, with higher ichthyoplankton densities in the Coxim and Taquari rivers, particularly between November and January. Twenty-eight genera and/or species of fish were identified, including 10 long-distance migratory species. Egg density showed a negative correlation with water temperature and rainfall. For larvae, water transparency and rainfall were both significant, negatively influencing larval abundance. However, different species tend to occur in environments with distinct abiotic qualities. Yolk-sac, preflexion, and flexion larval development stages were distributed throughout the sub-basin, especially near the Pantanal. Considering the data and analyses presented in this study, the importance of connectivity between these environments, specifically between the plateau and Pantanal, is evident, highlighting the significance of the entire sub-basin for fish reproductive processes. Therefore, research focusing on the ecological processes influencing the distribution of ichthyoplankton offers valuable insights for ecosystem conservation and aids in effective environmental management.

Animal personalities are differences in behaviour among individuals of the same species that are consistent over time and contexts. The integration of animal personality into conservation actions is hampered by limited understanding of personality traits in non-model organisms. We estimated repeatabilities and correlations between behaviours in Nannoperca vittata (western pygmy perch), a threatened freshwater fish species endemic to south-western Australia, and, for comparative purposes, in Poecilia reticulata (guppy), a species frequently used in personality research. Each fish was measured four times for each of seven behavioural variables, presumed to reflect five underlying personality traits. Track length (TL) was used as a measure of activity; time spent in a risky zone (RZ) and time to emergence (ET) for boldness; latency to approach a novel object (LA) and time spent close to the object (TS) for exploration; time spent close to a mirror (CV) for sociability and number of attacks at the mirror (AT) for aggression. Four behavioural variables (TL, RZ, ET and CV) were significantly repeatable in N. vittata and also in P. reticulata. There was a lack of concordance in phenotypic and among-individual correlations between variables in both species, emphasising the importance of partitioning trait covariances to infer behavioural syndromes. Significant among-individual correlations were found between activity, boldness and sociability variables in N. vittata, consistent with a proactive-reactive personality axis, but not in P. reticulata. Personality variation should be considered in conservation actions for N. vittata, particularly with respect to unintended consequences of domestication selection in captive breeding and release.

Fish assemblages, defined by taxonomy or functional traits, –respond to regional and local habitat variation. Our hypothesis was that fish assemblages could be best predicted using reach-scale (RS) hydrology variables over valley-scale (VS) hydrogeomorphology variables for US and Mongolian rivers. We further predicted that fish traits were predicted better by RS than VS variables. We evaluated the FS and VS hydrogeomorphologies of rivers in the United States and Mongolia in each of three ecoregions: grassland, forest and endorheic. Fishes were collected using a backpack electrofisher, following standard protocols. Constrained ordination analyses were conducted at three scales: among continents, by continents and by individual ecoregions within continents. We found no significant difference in mean variation explained by VS versus RS or by taxonomy versus traits. Ecoregions differed in factors contributing to fish assemblage patterns, likely a result of differences in hydrogeomorphology, hydrological connectivity and historical influences. We found that fish assemblages were structured by hydrogeomorphic processes occurring at VS and RS, and that variables predicting fish assemblages varied with scale and whether fishes were classified by taxonomy or traits. Although anthropogenic impacts were substantially higher for western US rivers than for Mongolian rivers, we were unable to detect strong differences in our ability to predict fish assemblage variation from RS and VS habitat variables.

The development of diverse capture mechanisms during foraging allows predators to select their preys and succeed in their capture, with the least energy expenditure possible. In this context, we seek to understand how prey selection mechanisms exhibited by freshwater fish piscivores relate to their foraging mode. The study was carried out in the floodplain of the Upper Paraná River, where fish were captured from March 2006 to June 2013. The fish were identified and measured, their stomachs were removed, and the stomach contents were analysed. Quantile regressions were used to evaluate possible effects and relationships between the sizes of piscivores and their prey. A significant positive effect on the predator–prey size relationship was observed, indicating an increased size of consumed prey with increased size of piscivore, mainly for Acestrorhynchus lacustris, Hoplerythrinus unitaeniatus, Hoplias intermedius, Hoplias mbigua, Hoplias sp. 2, Pseudoplatystoma corruscans, Rhaphiodon vulpinus and Salminus brasiliensis. Ambush predators were more likely to consume slow-moderate and fast prey, while pursue predators only consume fast prey. Several mechanisms can influence a piscivore's foraging behaviour, and body size is an important factor for both the piscivore and its prey. From the prey's point of view, the way they swim and the complexity of the habitat are important characteristics to ensure their survival. For piscivores, the foraging mode will influence the type of prey consumed, depending on the prey's swimming mode.

Isolation and limited migration among populations and differences in the environments they inhabit set up conditions for population differentiation of life-history traits, even across a regional spatial scale, such as a statewide landscape of lakes and reservoirs. Our objective was to understand how largemouth bass (Micropterus nigricans) life histories differ across a regional spatial scale (Ohio, USA) and whether environmental differences are influencing this variation. To address this, we (1) described spatial variation in largemouth bass life-history traits, with a specific interest in potential correlations between early-life growth and later-life traits and (2) tested whether life-history traits can be predicted by reservoir characteristics. We found two groups of correlated population traits: the inverse relationship of early-life growth rate with population density and asymptotic length and the positive relationship between adult size and asymptotic length. Early-life growth had a positive relationship (and population density and asymptotic length had a negative relationship) with littoral habitat availability and other environmental conditions expected to enhance early growth. Despite the strong influence of reservoir characteristics on life-history traits in our analysis, the most plausible model could not give precise predictions of these life-history traits, suggesting that the availability of data on other aspects of the populations and environments may improve our ability to understand life-history differences. Overall, our results suggest that, even among recently separated populations, we should expect differences in growth patterns and that we cannot understand drivers of these differences without considering possible correlations in growth patterns across the lifespan.

Comparisons between contemporary and historic surveys are useful in assessing how fish assemblages respond to anthropogenic stressors. When these stressors degrade aquatic environments, assemblages often experience biotic homogenization. The Strawberry River flows through the Ozarks of northern Arkansas and has been subject to both pasture land use conversion and constructed waterbodies which can degrade aquatic environments and alter fish assemblages. We investigated how fish assemblages in the Strawberry River have changed over a 35-year time span in response to pasture land use and constructed waterbodies. We found evidence of both taxonomic and functional homogenization of fish assemblages from the mid-1980s to 2019. This shift towards homogenization was primarily driven by increases in both site occurrence and abundance of generalist centrarchid species (associated with land use practices) and headwater specialist species (likely related to increased intermittency upstream). We created a composite variable using principal component analysis that represented pasture land use and constructed water body metrics because of their close relationship with each other. We found evidence of early functional differentiation associated with this composite variable; however, we found that over time fish assemblages ultimately experienced greater levels of homogenization associated with this same variable. This pattern of biotic homogenization associated with species additions suggests the Strawberry River is at a tipping point along a subsidy stress gradient, and in the future, we expect to see losses of specialist endemic species if conservation actions are not taken.

Nesting animals require information about their environment to place nests in optimal locations. This information can either be derived from an animal's previous experiences (private information), or it may be gained through the observation of the success of conspecifics (public information). This use of public information to locate suitable nesting sites has been explored in birds but not fishes. Many fish construct nests to protect their offspring, and the utilisation of public information could be a suitable strategy for determining which nesting locations would maximise fitness. We studied public and private information use in the bluehead chub, a species of nesting leuciscid in the Southeastern United States, by observing nesting activity and measuring habitat variables along a 0.65 km reach of Toms Creek in Blacksburg, Virginia. We clustered activity data and created generalised linear models to determine if bluehead chubs construct nests within discrete nesting periods during the spawning season and if they use public or private information to select nest sites between these periods. Our results suggest that bluehead chubs construct nests periodically within a single spawning season and use a combination of public and private information when determining suitable nesting sites from one nesting period to another. This study provides some of the first evidence suggesting public information use for nest site selection in a species of fish and opens up a new frontier of research into public information use among fishes.

The management of intraspecific diversity in many species is usually disconnected from eco-evolutionary processes happening in natura. A classic example is embodied in the problem of introgression in hybridized fish populations, wherein management practices are generally unaware of any selective process at work, and therefore generally rely on numbers (adding or removing individuals) to reduce introgression. Such an example can be observed in the French Alps, where native Mediterranea (MED) brown trout have been highly introgressed through decades of stocking with domesticated Atlantic (ATL) brown trout. Recently however, new results shed light on a potential selective mechanism that may affect differentially the fitness of MED and ATL genes depending on the environment (GxE interaction). Using a demogenetic agent-based model able to account for such GxE interaction, we simulate a management scenario implemented in 2005 by some biodiversity managers and scientists, who attempted to restore the Mediterranea gene pool using translocation of near pure MED individuals in Atlantic-dominated areas. We show that the model is unable to recreate the observed introgression dynamics if the GxE interaction is not included. This finding implies that (i) eco-evolutionary mechanisms can have large effects on introgression dynamics on very short time scales and (ii) management of intraspecific diversity should increasingly rely on these natural mechanisms, so as to improve management targets and facilitate adaptation to rapid environmental changes.