Substratum selection by different sizes of spined loach Cobitis sp.

We tested substratum selection by different sizes of spined leach Cobitis s p. in a small lowland stream. Smaller individuals preferred substrate of sm aller particle sizes than did larger conspecifics, suggesting that the dist ribution of juvenile spined leach is related to the size distribution of al luvia. Substrate size preferences also varied with season. The relationship between substratum particle size and fish size was significant only for th e finest fraction (dis). No preference were observed with respect to other environmental variables (organic matter content, depth, water velocity).