Climate is a major driver of species distribution and biological invasions worldwide. In this study, we combined the catches of a widespread and invasive species, the common carp (Cyprinus carpio), with climate data to assess the importance of climate variables on the ability of the species to maintain self-sustaining populations in European lakes. Data were collected on common carp populations in 378 lakes in six European countries over a 16-year period (551 sampling campaigns). All catches followed the same standardized sampling procedure (European CEN gillnets). Climate data consisted of daily averages of air temperature and precipitation. Population self-sustainability was determined by the relative catches of different size classes and the presence of juveniles. The climate data were used to train a classification tree model to characterize the effects of climate on common carp population viability. Results indicated that climate is an important predictor of common carp population viability, which is particularly enhanced under dry conditions and elevated temperatures during spring and summer months. Areas of high population viability strongly overlapped with the invasive range of the species. According to Intergovernmental Panel on Climate Change (IPCC) climate projections, some areas where common carp currently have a low probability of maintaining viable populations will shift toward climatic conditions that enhance their viability and invasion potential.

The complementarity of two high-resolution spatiotemporal acoustic methods, telemetry and hydroacoustics, was evaluated during the same time window to obtain fish distribution in a canyon-shaped reservoir, the Bariousses Reservoir (France). These methods act at an individual scale for telemetry and a community scale for hydroacoustics. The temporal scales are also different: telemetry offers continuous and long-term monitoring while a snapshot view is given by hydroacoustics. Day and night hydroacoustic surveys were carried out in this reservoir, during a 24-hour period in spring, using vertical and near-surface horizontal beaming. During this time window, 11 adult fish (length: 22-57 cm) from three species (roach, perch, and pikeperch) were tracked by telemetry. Four metrics were calculated with data collected by application of the two methods: distances to the nearest bank, distances to the tributary, fish depth, and bottom depth at the location. The contrasting (distance to the nearest bank, bottom depth) or partially similar results (distance to the tributary, fish depth) can be explained by the limitations associated with each method. The results obtained with telemetry are very sensitive to the species composition and the size of the tagged fish. The number of fish located in the epibenthic areas of the reservoir can be underestimated by hydroacoustics. This preliminary case study highlights that these methods act in a complementary way and their simultaneous use can provide better information on fish spatial distribution.

The aquatic ecosystem structuration in human influenced environment, is closely dependent of the associated uses, which are generally fluctuant. We conducted an extended field monitoring on a reservoir under water level fluctuations (WLF), in order to study the responses of fish fauna to changes in environmental conditions. The study design was based on a monitoring of fish behaviour by telemetry in a reservoir with a particular attention to the littoral zone because of its front line position during WLF. The results of this study, which was conducted on the Bariousses reservoir, located on the Vézère river (Corrèze, France), are summarized in this article. The study revealed that WLF induced a temporal variability in the littoral zone surface. In addition, we observed a gradual decline in structural complexity of littoral habitats with a tendency towards homogenisation (dominance of fine substrates and absence of vegetation) in relation with the drop in water level. Behavioural individual responses of pikeperch, perch and pike were highly variable in relation to environmental fluctuations. Temperature and photoperiod were the two main parameters controlling fish activity and spatial distribution. Water level affected part of fish assemblage: some individuals were more mobile and left the littoral zone when inshore habitats were less complex (low water level).

The use of the CEN (European Committee for Standardization) standard method for sampling fish in lakes using multi-mesh gillnets allowed the collection of fish assemblages of 445 European lakes in 12 countries. The lakes were additionally characterised by environmental drivers and eutrophication proxies. Following a site-specific approach including a validation procedure, a fish index including two abundance metrics (catch per unit effort expressed as fish number and biomass) and one functional metric of composition (abundance of omnivorous fish) was developed. Correlated with the proxy of eutrophication, this index discriminates between heavily and moderately impacted lakes. Additional analyses on a subset of data from Nordic lakes revealed a stronger correlation between the new fish index and the pressure data. Despite an uneven geographical distribution of the lakes and certain shortcomings in the environmental and pressure data, the fish index proved to be useful for ecological status assessment of lakes applying standardised protocols and thus supports the development of national lake fish assessment tools in line with the European Water Framework Directive.

Launois L, Veslot J, Irz P, Argillier C. Selecting fish‐based metrics responding to human pressures in French natural lakes and reservoirs: towards the development of a fish‐based index (FBI) for French lakes. Ecology of Freshwater Fish 2011: 20: 120–132. © 2010 John Wiley & Sons A/SAbstract – Fish‐based indices of biotic integrity have been developed for many lotic systems but remain scarce for lakes. The goal of this study was to assess the responses of lentic fish assemblages to anthropogenic pressures when environmental variability was controlled for and to compare them between French natural lakes and reservoirs. Environmental features, catchment‐scale anthropogenic descriptors and fish data were collected from 30 natural lakes and 59 reservoirs throughout France. Functional fish metrics were regressed against both anthropogenic variables and the natural environmental conditions. Our results show that fish assemblages are appropriate ecological indicators for both natural and artificial lakes. They underline the necessity to control for the environment when developing indices at broad geographical scales. The relevant metrics differ between natural lakes and reservoirs, which challenges the attempts to use natural systems as references to assess the ecological potential of artificial ones.

Functional diversity is the diversity of species traits in ecosystems. This concept is increasingly used in ecological research, yet its formal definition and measurements are currently under discussion. As the overall behavior and consistency of functional diversity indices have not been described so far, the novice user risks choosing an inaccurate index or a set of redundant indices to represent functional diversity.In our study we closely examine functional diversity indices to clarify their accuracy, consistency, and independence. Following current theory, we categorize them into functional richness, evenness, or divergence indices. We considered existing indices as well as new indices developed in this study. The new indices aimed at remedying the weaknesses of currently used indices (e.g., by taking into account intraspecific variability). Using virtual data sets, we test (1) whether indices respond to community changes as expected from their category and (2) whether the indices within each category are consistent and independent of indices from other categories. We also test the accuracy of methods proposed for the use of categorical traits.Most classical functional richness indices either failed to describe functional richness or were correlated with functional divergence indices. We therefore recommend using the new functional richness indices that consider intraspecific variability and thus empty space in the functional niche space. In contrast, most functional evenness and divergence indices performed well with respect to all proposed tests. For categorical variables, we do not recommend blending discrete and real-valued traits (except for indices based on distance measures) since functional evenness and divergence have no transposable meaning for discrete traits. Nonetheless, species diversity indices can be applied to categorical traits (using trait levels instead of species) in order to describe functional richness and equitability.

Dehais C, Eudeline R, Berrebi P, Argillier C. Microgeographic genetic isolation in chub (Cyprinidae: Squalius cephalus) population of the Durance River: estimating fragmentation by dams. Ecology of Freshwater Fish 2010: 19: 267–278. © 2010 John Wiley & Sons A/SAbstract – Weirs and dams are wide spread throughout the world’s river systems. The most direct effect of these barriers is the limitation of organism movements, i.e., the alteration of connectivity by fragmentation of the aquatic habitat. Whereas the impact of fragmentation on migratory fish species has been well studied, insights on nonmigratory species are still needed. In particular, knowledge on the effects of dams on cyprinid populations at the watershed scale is lacking. Therefore, we studied the genetic structure of eleven chub (Squalius cephalus) samples lined up in the highly fragmented Durance River (France). Using five microsatellite loci, we show that even if the overall genetic differentiation is low, isolation by distance does occur and that genetic diversity increases from upstream to downstream. Dams seem to participate jointly with waterway distance in the explanation of this pattern. However more precise conclusions cannot be made. Guidance for future studies are given.

In order to assess the ecological status of water bodies, the Water Framework Directive requires the development of bioindicators adapted to homogenous ecosystems with respect to their environmental conditions. A lake typology based on environmental parameters known to influence fish communities is presented; a first approach to select fish based metrics by analysing their response to the anthropogenic pressures exerted on the watershed is then described for two types of small French lakes, i.e. deep natural lakes at high altitude with shoreline development factors (SLDF) close to 1, and shallow reservoirs at low altitude, showing high SLDF. Our results are encouraging, because phytophilic and

Pour évaluer l’état des masses d’eau, la Directive Cadre Européenne sur l’Eau requiert l’utilisation de bioindicateurs adaptés à des systèmes homogènes d’un point de vue environnemental. Nous présentons ici une classification de plans d’eau basée sur des paramètres environnementaux naturels connus pour structurer l’ichtyofaune. Ensuite, un premier essai de sélection de métriques piscicoles, par analyse de la réponse aux pressions anthropiques s’exerçant sur les bassins versants, est décrit pour deux types de petits plans d’eau français, i.e. les lacs naturels plutôt profonds et de forme arrondie, situés à des altitudes moyennes et des retenues peu profondes, à berges découpées et situés à très faible altitude. Les résultats obtenus sont encourageants car les richesses en espèces phytophiles et tolérantes répondent bien aux pressions anthropiques. Cependant, cette approche présente des limites. En effet, certains types de milieux identifiés dans cette étude ne regroupent que peu de plans d’eau; d’autres conservent une certaine variabilité environnementale à même d’influencer l’ichtyofaune. D’autre part, le nombre de sites pas ou peu perturbés est parfois restreint, voire nul pour le groupe des retenues peu profondes, à berges découpées, de très faible altitude. Enfin, entre les différents groupes typologiques, les gammes de pressions observées, sont elles-mêmes distinctes. Ces résultats devront être validés mais la recherche d’une solution alternative à cette approche typologique, pour évaluer l’état des plans d’eau, devrait être envisagée.

1. While fish-based Indices of Biotic Integrity have been developed for a wide array of lotic systems, equivalent tools have seldom been adapted to the monitoring and assessment of lakes. Major difficulties arise in such work: (i) collecting data that allow statistically robust analyses, (ii) choosing the relevant variables to describe the biotic, environmental and anthropogenic data sets and (iii) assessing the relative importance of the latter two in explaining the former. The aim of the present paper is to produce such an assessment for the fish communities of the lakes of northeast USA. 2. Fish surveys, environmental features and catchment-scale descriptors of anthropogenic stresses (agricultural and urban land uses) were collected for 112 natural lakes. 3. Fish metrics, i.e. species richness and percentages of species belonging to reproductive, trophic, and tolerance guilds were regressed against anthropogenic variables then against anthropogenic variables and the natural environmental. 4. It was shown that failing to control for the natural environmental conditions in the IBI construction led to selecting metrics (% of intolerant species and % of omnivorous species) that did not display response to stresses when the environment was controlled for. Moreover, controlling for natural variability of the metrics allowed identifying the impact of agricultural land use on the % of diadromous species. 5. Fish communities appear valuable for the bioassessment of lakes. Appropriate statistical methods have proved that the natural variability in the bioassessment tools could be accounted for, thereby allowing assessments at multiple basins and ecoregions scales. This opens new perspectives for the development of IBIs for lentic systems in lake-poor regions, such as southern Europe, and therefore represents a significant contribution to the implementation of the European Water Framework Directive.

The stability and the precision of fish metrics obtained using CEN multi-mesh benthic nets are compared between twenty-seven natural and artificial French lakes. We show that the natural or artificial origin of the lake has no impact on the precision of the fish metrics provided by the method and it provides more precise catch data in French lakes than in the Nordic countries. The precision of abundances and biomass depends on fish density, and thus on the trophic status of the lake sampled. We also show that the sampling effort advocated by standard is appropriate in French lakes despite its underestimation of species number and disregard of marginal habitats. Nevertheless in deep lakes, the sampling effort could be reduced in the deeper layers which are never informative.

Thirteen pikeperch Sander lucioperca were implanted with acoustic transmitters and 10 were successfully tracked twice a week from March to early July in a drainage canal connected to a brackish lagoon located in the Rhône delta. Pikeperch was found in the main canal and in narrow tributaries, but never in the lagoon. Pikeperch avoided shallow parts of the canal and selected areas with high riparian vegetation (mainly trees). No between sexes differences occurred in habitat selection. At the basin scale, while both sexes remained in the upstream part of the canal during the spawning period, after spawning, females migrated downstream and also into the tributaries. This migration may have been induced by the movement of prey while males remained guarding the nests.

ABSTRACTAim To analyse the importance of local and regional influences on the patterns of species richness in natural and man‐made lakes and to infer the impacts of human‐mediated introductions on these patterns.Location France.Methods Species occurrence data were gathered for 25 natural and 51 man‐made lakes. Analysis is based on regression models of local richness against their related regional richness and lake environmental variables.Results Local native richness was mostly controlled by the regional richness. Conversely, local total richness was mainly explained by local variables. These statements apply to both natural and man‐made lakes. Lacustrine systems displayed weak resistance to invaders.Main conclusions Species introductions have apparently contributed to saturate fish communities in these systems even if no clear negative effect on the survival of native species (i.e. species extinction) is detectable so far.

Previous studies showed that only 20% of the variability in fish community structure in French reservoirs could be explained by site characteristics. In addition, no relationship was found between the relative abundance of species and stocking effort. Therefore, deliberate or uncontrolled introductions are likely to be the source of a great part of the observed communities. The objective of this study was to assess the importance of species introductions in French reservoirs. Fifty-one reservoirs were sampled to obtain species presence/absence data. Local native (LNaR) and non-native (LNNR) species richness were negatively correlated. LNaR was strongly correlated to the lake surface area, depth and catchment area, whereas LNNR was independent of environmental variables. Furthermore, LNaR was positively correlated to regional native richness. Conversely, local total richness was independent of regional total richness, but was related to the reservoirs’ environmental characteristics. It was hypothesised that the native fish communities in French reservoirs are unsaturated and species introductions lead to saturated communities.

The objectives of this paper are to describe the fish assemblages in French reservoirs and to relate them to the sites' characteristics. The results of 43 fishing surveys were collected and completed with environmental descriptors. Fish assemblages differ between salmonids-dominated mountain sites and lowland ones. The latter show higher species diversity and a distinction between rheophilic- and limnophilic-type communities. This distinction can be explained by the reservoir age, location in the catchment and depth. The response of fish communities to these variables was investigated by canonical correspondence analysis. It shows that rheophilic species are typically abundant in upper basin, deep and recently created reservoirs. The fish community response to the aging process corresponds to an addition of lowland standing waters species and an extinction of the native riverine ones. The structuring role of the sites' depth, location and age is discussed, considering their relationship with the water body trophic status.

This chapter contains sections titled: Introduction Materials and methods Results Discussion Acknowledgements

Few research has been carried out on French lacustrine fish communities. In a first part, we presented the results obtained by analysing fish communities in natural lakes and reservoirs located over 1500 m in altitude (ARGILLIER et al., 2002b). The present article follows a similar analytical approach but deals with lowland sites.Both natural and man-made lakes display a fish gradient from upstream to downstream sites. The species range from gudgeon, rainbow trout and brown trout, then pike and roach, perch and eventually pikeperch. The distinction between the fish communities of natural lakes and reservoirs relies upon the abundance of several species. Whitefish and arctic charr are lake dwellers whereas the abundances of black bullhead, French nase and barbel are maximum in reservoirs. The fish communities can be related to the location of the sites in their catchment. Some results suggest that the physical features of littoral habitats could contribute to explain the observed communities. Further works should take into consideration complementary descriptors of both fish communities and environmental features.