Habitat shifts of perch larvae as survival strategy

Abstract

Perch (Perca fluviatilis L.) spawn in lakes, rivers and estuaries and even in the brackish water of the Baltic Sea. In the outer archipelago of the Baltic the selection of unexposed spawning sites can be explained by the genetic component in larval dispersal and the return to inshore waters. The larvae were found to be active, at least in initiating the dispersal. Nevertheless, currents probably aid in the dispersal process. Although the shift back inshore has been documented in all lakes studied, it was here noted to be a gradual process. The timing of the return to littoral areas varies somewhat from one lake to another, and it may also depend on the size and trophic state of the lake. Perch thus appears to be adapted to variable environments. It is suggested that the shift may be a sensitive period in the formation of year-class strength, since the 0+ perch are then more exposed to predator pressure. The dispersal strategies of roach and perch larvae differed, and only after perch returned to the littoral did the distribution area of 0+ perch overlap with that of 0+ roach.