Seasonal changes in fish abundance, biomass and species richness in the littoral zone of a large European lake, Lake Constance, Germany

Abstract

Seasonal changes in the abundance, biomass and species richness of fish in the littoral zone of Lake Constance were examined. Electric fishing was conducted in three depth strata at six different sampling sites within the littoral zone from November 1991 to Februar 1993 during daytime. Minimal abundance and biomass values were observed in February with 3.9 (SD ±. 4.2) ind 100 m[-2] and 12.7 (SD ± 13.8) g-wet . 100m[-2]. Maximal abundance values were observed in August with 119.5 (SD ± 88.5) ind . 100 m[-2], maximal biomass values in May with 903.9 (SD ± 1942.6) g-wet . 100 m[-2]. The influence of individual habitat variables on the littoral fish community was examined by canonical correlation analysis. Seasonal changes in total fish abundance, biomass and species richness were mainly explained by seasonal changes in water temperature followed by lake level. For the individual species, different substrate characteristics such as sediment type or the amount of large stones lying on the bottom providing shelter were also found to be important. However, these variables often influence fish abundance and biomass only within a range that is predefined by water temperature. Different patterns were found for the two benthic species. burbot (Lota lota) and stone loach (Noemacheilus harbatulus). The distribution of both species was mainly correlated with the availability of gravel substrate and shelter and mostly independent of littoral water temperature. Burbot larger than >5 cm TL emigrated from the littoral into deeper adjacent areas during summer when water temperature increased above a certain threshold, indicating an upper thermal threshold for this cold stenothermal species.