J. Sarvala et H. Helminen, YEAR-CLASS FLUCTUATIONS OF PERCH (PERCAFLUVIATILIS) IN LAKE PYHAJARVI, SOUTHWEST FINLAND, Annales zoologici Fennici, 33(3-4), 1996, pp. 389-396
Year-class variation of perch (Perca fluviatilis), a potentially impor
tant predator of larval and juvenile vendace (Coregonus albula), was a
ssessed in Lake Pyhajarvi, based on a two-stage sampling of the winter
seine net catches in 1989-1995. From these data, we could estimate re
lative abundances of perch year-classes for the years 1986-1993. Durin
g this period, the year-classes of 1988 and possibly 1992 were strong.
The year-class 1988 dominated numerically in catches from 1990 to 199
3 and the year-class 1992 in 1994 and 1995. Year-class strength of per
ch was positively associated with the June-August temperature sum.