Seasonal changes in abundance and age structure of burbot Lota lota (L.) and stone loach Barbatula barbatula (L.) in the littoral zone of a large pre-alpine lake

Seasonal changes in the abundance and age structure of the stone leach and burbot populations in the littoral of Lake Constance! Germany were examined . The abundance of both species was lowest during the summer months and hig hest during autumn. The stone leach population in the littoral comprised ag e classes 1 to 3 plus, in autumn, age class 0. The burbot population showed distinct seasonal changes in both length and age composition. During sprin g and summer, only age class 1 was present in the littoral whereas, in autu mn, only age class 0 was caught. This remarkably strict habitat segregation of two age classes by season is discussed with respect to a possible mecha nism for avoiding conspecific predator risk in a cannibalistic species.