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The biological and biochemical effects of temperature on life-history strategy of female bullhead Cottus gobio were investigated. Fish from two populations (Bez Basin, south-east France) experiencing contrasted thermal environments ( i.e. more or less stable) were reared during 4 months at three distinct temperatures (7, 9 or 12° C). Both somatic (soma fresh mass and muscle triglyceride content) and reproductive (gonad fresh mass, fecundity, mean diameter of eggs and gonad triglyceride content) indicators were examined. Mixed models indicated that an increasing temperature had significant negative effects on all life-history indicators except for soma fresh mass. Differences in life-history strategy with regard to muscle and gonad triglyceride contents, however, suggest that populations experiencing more variable thermal environments may be better adapted than others to cope with an increasing temperature. These findings may have important implications for C. gobio populations, within the context of climate warming. [ABSTRACT FROM AUTHOR]

Point abundance sampling, using electrofishing, for stone loachBarbatula barbatulain two habitats, riffle and pool, showed that there was no difference in density between the two habitats. The density of fish increased significantly(1·8 fold;P < 0·001) when the substratum of small cobbles(128–256 mm) was removed and electrofishing repeated. [ABSTRACT FROM AUTHOR]

Ibarra AA, Park Y-S, Brosse S, Reyjol Y, Lim P, Lek S. Nested patterns of spatial diversity revealed for fish assemblages in a west European river. Ecology of Freshwater Fish 2005. © Blackwell Munksgaard, 2005 The longitudinal distribution of fish assemblages across a large west European river basin, the Garonne river (south-west France) were investigated using a self-organising map. This nonlinear statistical method was employed to classify sampling sites according to their species composition. We found three main nested patterns in an aggregated hierarchy: a replacement and succession of species along a gradient without defined boundaries, four main zones of fish assemblages and an upstream-downstream shift of fish communities. We suggest that fish assemblages are too complex to be identified with a single species as in the zonation model, and that the diversity patterns found might be part of the same ecological process influencing fish assemblages on different spatial scales. Thus, discrepancies in the analysis of longitudinal patterns of fish communities in streams may have been basically a matter of local conditions and of conceptual perception. [ABSTRACT FROM AUTHOR]