In this study, capture–mark–recapture statistics were applied to spatial recapture histories to assess the intensity of fish restricted movements along the longitudinal axis of a river using a previously described model for survival and recruitment analysis. Adapting the stopover estimation method to spatial data, movement probabilities were then used to estimate space used at the population scale. This capture–recapture estimates of space used in streams (CRESUS) method may thus be seen as a complementary tool of classic home range methods and should be used to explore the consequence of behavioural strategies on population mechanisms. We propose a methodological example where movements and space use strategies of a Zingel asper (percid) population in the Beaume River (Ardèche, France) were directly estimated at the population scale taking account of the effects of different biotic or abiotic factors. Results showed differences in Z. asper space use patterns among sexes, periods of biological cycle (growing and spawning period), and types of mesohabitat. Downstream movements were more important during the spawning period and by the way the riffle was more intensively used.

Marine fish wild stocks are known to be heavily depleted by overfishing and flatfish species are no exception. Wild catches being soon insufficient for responding to consumer demand, the cultivation of marine species appeared as a logical response to the need of seafood. Nevertheless, fish aquaculture also entails major impacts on wild populations from which genetic ones are now better known. The hybridization between domestic and native strains potentially have a genetic impact on recipient populations as long as 1) domestic populations are distinct from native wild ones (through domestication process, genetic improvement of captive stocks) and/or 2) the native wild populations are structured (metapopulation structure, local adaptation). Some of the flatfish species exhibit population differentiation and even local adaptation and the release of domestic genetically modified fishes (selected, transgenic) could threaten their survival in case of introgression. The impact of aquaculture on flatfishes is probably still low as land-based farms and low production levels guaranty low rates of escapes and therefore limited contacts between wild and farmed strains. However, flatfish aquaculture is regarded by experts as a rapidly growing domain that will greatly develop soon. In our opinion, this perspective, added to the quite good performances of farmed flatfishes when released into the wild, fully justifies a stronger interest from the scientific community to the conservation of their wild stocks.

ABSTRACT1. Zingel asper (a percid) is a highly endangered endemic fish of the Rhone catchment (France). Scale reading was used to estimate age and growth rates in one of the two last remaining populations that are still present in relatively high densities (River Beaume).2. Scale reading was validated for the first time in Z. asper by comparing back-calculated lengths from scale annual increment to actual lengths obtained by individual mark-recapture monitoring. The impacts of age or sampling site on individual growth rates were explored using generalized linear models.3. No major discrepancy was observed between actual and back-calculated lengths. Longevity of Z. asper was inferred from the age data and did not exceed 3 years. Results showed variation in growth rates among ages (20 times higher for 1þ fish than for 2þ or 3þ fish) and also among sampling sites.4. The present work provided the first estimates of annual growth rates in the Beaume population. This study also showed that scale reading allowed a valuable trade-off between accuracy and conservation imperatives that often imply avoiding invasive techniques such as the implantation of passive integrative transponders.5. Scale reading will be a valuable tool for future ecological studies in Z. asper and will help in developing conservation strategies for this species as longevity and growth patterns are two lifehistory traits of major importance for the management of endangered populations.

By combining biotin-enrichment protocol and next generation pyrosequencing, through 454 GS-FLX Titanium technology, 55 polymorphic microsatellites loci with perfect motif were isolated from the Rhone streber (Zingel asper), a critically endangered European fish species. Eight multiplex PCR kits were optimised in order to genotype a total of 58 polymorphic loci, including three previously published loci. The level of genetic diversity was assessed for 68 Z. asper, 30 Sander lucioperca, 33 Perca fluviatilis and four Gymnocephalus schraetzer individuals. Amplification success was also assessed on Romanichthys valsanicola and Zingel streber using single individuals. These markers will be useful to investigate the population structure of the highly fragmented Rhone streber. They represent a powerful tool for conservation issues and evolutionary approaches of this endemic species.Moreover, part of our markers demonstrated applicability to other percid species, allowing for potential applications to fisheries and aquaculture management.