Stage-dependent spatial synchrony revealed for fish populations in the Garonne River (SW France)

This study aimed to establish the presence of spatial synchrony for three riverine fish populations (stone loach Barbatula barbatula L., European minnow Phoxinus phoxinus L. and gudgeon Gobio gobio L.) in two spatially-close sites of the Garonne River (SW France). Sampling was carried out by electrofishing from 1994 to 1999. The fish were split into two age classes (0+ and > 0+) using length-frequency distribution analysis. No autocorrelation was present in our time series. There were significant correlations of densities between sites for stone loach (> 0+) and gudgeon (0+), but not for European minnow. A significant positive relationship was observed between maximal flow values and 0+ gudgeon density. No significant associations between flow variables and density were observed for stone loach. These results emphasize the role of external factors in effecting population dynamics, and suggest that their influences differ according to life stage and life-history characteristics.