Morphology, Physiology, Behavior, and Ecology of Perca fluviatilis L. and P. flavescens Mitchill

A review of literature on Perca fluviatilis and P. flavescens indicated one difference (in the position of the predorsal bone) sufficient to maintain their separateness as species. Otherwise they are overwhelmingly equivalent biologically. Their distributions are limited by the same effects of temperature, current speed, salinity, and dissolved oxygen. They are similar in gonadal development and age at first maturity; in the effects of water temperature and latitude on spawning time, and of environmental fertility on fecundity; in spawning behavior, fecundity, and the course of larval development. Growth capacities are similar and their expression subject to population density and temperature in the same way. Both species are adapted to a diet of small live animals, but will take whatever is available; cannibalism is characteristic, and may begin at the same early feeding stage. The two species show similarities in diurnal periodicity of feeding and in total food consumption. They also have the same patte...