Year class variation in fluctuating asymmetry in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake

Fluctuating asymmetry is the random deviation from perfect bilateral symmetry owing to developmental perturbation, proposed as an indicator of sublethal environmental effects. This was measured in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake. Eleven paired meristic and morphometric characters were scored for fluctuating asymmetry. Level of fluctuating asymmetry differed significantly between year classes for two of the meristic characters, lower extra gill rakers and upper extra gill rakers, and also for an index summarizing number of asymmetric meristic characters per individual. This year class variation in fluctuating asymmetry is probably due to large variation in water quality during early development of perch embryos in spring. For future work on fluctuating asymmetry on fish we recommend the use of as many year classes as possible in the analyses.