Between and within-lake variations in morphology of perch Perca fluviatilis were studied in four humic lakes in eastern Finland. Perca fluviatilis were more streamlined and smaller headed in a lake with the highest abundance of cyprinids, but lowest abundance of predators (Lake Tuopanjärvi), indicating adaptation to planktivorous feeding and low predator density. Highest bodied fish were found from a lake with the lowest cyprinid but highest predator abundance (Lake Koppelojärvi), which conversely indicates adaptation to more effective predator avoidance. Furthermore, the length of the paired fins was longest in Lake Kinnasjärvi and Lake Tuopanjärvi, where the abundance of benthic macroinvertebrates was lowest, suggesting selection for more effective benthivory. Clear morphological differences of P. fluviatilis between habitats were found only in Lake Kinnasjärvi, whereas in Lake Koppelojärvi and Lake Tuopanjärvi only the length of the paired fins differed and in Lake Harkkojärvi no differences were found. Taken together, these results suggest that inter and intrapopulation morphological differences are probably highly dependent on different biotic factors (i.e. predation risk, resource availability and competition). Spatial and temporal variations in these factors may have a great effect on body morphology of P. fluviatilis.
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Document Type: Regular Paper
Ecological Research Institute, Faculty of Biosciences, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland
Information Technology Centre, University of Kuopio, P.O. Box 1627, FI-70211 Kuopio, Finland
Publication date: 01 March 2010