BODY MORPHOLOGY OF CRUCIAN CARP CARASSIUS-CARASSIUS IN LAKES WITH OR WITHOUT PISCIVOROUS FISH

Crucian carp Carassius carassius was sampled during 1993 and 1994 in 2 1 lakes and ponds in east Norway. In 10 of these lakes and ponds no pi scivorous fish species was present, and in the remaining 11 lakes and ponds predators such as perch Pei-ca fluviatilis, pike Esm lucius, and trout Salmo trutta were common. In general, crucian carp was larger i n the lakes with predators than in those without predators. The relati ve body depth (body height/body length) of crucian carp was significan tly deeper in populations sympatric with predators (mean 0.358), compa red to allopatric populations (mean 0.286). The variation in relative body depth was larger among the sympatric populations than among the a llopatric populations. The observed difference in relative body depth may be due to 1) predator induced changes in body morphology, 2) incre ased growth rates in lakes containing predator due to reduced intraspe cific competition, and 3) size-selective predation.