H. Helminen et J. Sarvala, POPULATION REGULATION OF VENDACE (COREGONUS-ALBULA) IN LAKE PYHAJARVI, SOUTHWEST FINLAND, Journal of Fish Biology, 45(3), 1994, pp. 387-400
Previous time series analysis on vendance population dynamics in Lake
Pyhajarvi, 1971-1990, revealed a 2-year cycle in year-class strength,
implying powerful density-dependent regulation. Here we have extended
this analysis by using multiple regression models to test whether the
recruitment series is influenced by density-independent factors. We ch
ose population size with a lag of 1 year as the density-dependent fact
or; the density-independent factors were the summer water temperature
with a lag of 2 years (temperature sum for June, July and August, indi
cating the year-class strength of predators) and the temperature-deriv
ed length of the larval period of vendace. For the years 1972-1990 the
coefficient of determination (r2) of this regression model was 0.77.
We suggest that the basic mechanism producing a persistent 2-year cycl
e of vendance in Lake Pyhajarvi is the asymmetrical food competition b
etween age groups. The abundance of predators in the lake and the warm
ing of the water after the hatching of larvae in spring together deter
mine the final year-class strength of vendace.