Abundance, depth distribution, diet composition and growth of perch (Perca fluviatilis) and burbot (Lota lota) larvae and juveniles in the pelagic zone of Lake Constance

Abstract

Abstract— Surveys of larval and juvenile fish in the pelagic zone were made in Lake Constance between April and July 1994 with a plankton net. Perch (Perca fluviatilis) and burbot (Lota lota) were caught persistently, while other species were found only occasionally. Perch and burbot coexisted in the pelagic zone; both species were found first in mid‐May, reached peak density in June, and disappeared from the pelagic zone in late July. However, the abundance of perch was much higher than that of burbot. Perch were distributed mainly near the surface, whereas burbot were more abundant at the deeper strata of 5 and 10 m, exhibiting habitat segregation. Perch fed mainly on copepods and positively selected them during their first month of life, and afterwards, they consumed principally on Daphnia, while burbot fed mainly on copepods and positively selected them throughout the study period. Perch grew significantly faster than burbot, and the mean lengths of perch were about 3 times greater than that of burbot in July. The results demonstrate that perch and burbot were the main species of pelagic larvae in Lake Constance between May and July, and that the two species differed somewhat in depth distribution, diet composition and growth.