Ecology of Freshwater Fish最新文献

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.

Large dams significantly impact river ecosystems by disrupting connectivity, altering physicochemical variables, and modifying flow regimes. These modifications influence the spatial and temporal dynamics of biological processes and species distributions. While much research has focused on potamodromous species, there remains a gap in understanding the recovery gradients of resident species in dam-altered rivers. This study examines the responses of larvae of a resident species, the mandarin fish (Siniperca chuatsi), to environmental alterations caused by the Three Gorges Dam (TGD) in the middle reach of the Yangtze River. We hypothesized that larval abundance, feeding, growth, and survival would exhibit longitudinal recovery gradients, improving with the increased distance from the TGD. Our results confirm this hypothesis, showing that larvae further from the TGD exhibited higher abundance, increased feeding intensity, enhanced growth rates, improved survival rate, and earlier peak abundance and hatching dates. Key environmental factors, including water temperature and discharge, increased downstream, while transparency decreased. Major tributary inputs significantly contributed to these recovery gradients. The observed longitudinal gradients in larval attributes mirrored environmental changes, underscoring the TGD impact on population recruitment. These results highlight the broader implications of dam-induced changes on resident species recruitment, potentially affecting entire fish communities. Our study contributes to understanding the distinct spatial patterns of population trends, providing valuable insights for designing more effective conservation and management practices for resident freshwater fishes in large regulated rivers.

Hybridisation is a complex process that begins with mating. Females have more to lose with each hybrid fertilisation than males, so they should avoid it. Even if females choose con-specific males as preferred mates, they often cannot control which additional males release sperm during spawning. Polyandry is ubiquitous and may result in hetero-specific sperm competition between males of different species. In such cases, cryptic female choice (the ability to bias paternity towards certain males under sperm competition) is the last line of defence to prevent hybridisation of her eggs and is highly adaptive if it enables con-specific sperm preference. Such seems to be the case with the hybridisation of Atlantic salmon (Salmo salar) and brown trout (S. trutta) in their native Europe. Under hetero-specific sperm competition, hybrid fertilisations in these fish are reported to be reduced via ovarian fluid-mediated cryptic female choice. It is not known, however, whether the strength of this mechanism is dependent on reinforcement and thus, the historical sympatry/allopatry of hybridising populations. Brown trout are one of the world's worst invasive species. Ecological impacts arise through competition with other species (e.g. Galaxids in the southern hemisphere, Oncorhynchus in western North America). Eastern North America contains native salmonids that evolved in the absence of brown trout but have gametes that are compatible. The 140 -year-old brown trout invasion of Newfoundland is ground zero to study these potential interactions. Their relatively low spread rate across the island may be the result of inherent poor productivity, but data suggest it could also be a function of hybridisation with native Atlantic salmon and brook char (Salvelinus fontinalis).

Sexual dimorphism, the phenotypic differences between males and females within a species, is widespread in the animal kingdom. This study investigates the extent of sexual dimorphism and species divergence in external morphology in two closely related freshwater fish species, Devario malabaricus and D. micronema, in Sri Lanka. Devario malabaricus, a habitat generalist, inhabits a wide range of aquatic environments, while D. micronema, a habitat specialist, resides in shaded rainforest streams. The study reveals size differences between the two species: D. malabaricus is consistently larger than D. micronema. However, there are no size differences between the sexes within each species. Several additional morphological traits, such as head length, interorbital width, predorsal length and postdorsal length display divergence between the species as well as between the sexes within each species; these patterns are also consistent across populations. The sexually dimorphic traits are similar between the two species despite their distinct ecological habitats. However, Devario malabaricus exhibit stronger sexual dimorphism compared to D. micronema, supporting the prediction of a positive relationship between the extent of sexual dimorphism and ecological generalism. The study highlights the importance of considering sexual dimorphism in morphometric comparisons in taxonomic studies of Devario and suggests that divergent selection between the sexes contributes to morphological variation in this group.