L. Wu et Da. Culver, DAPHNIA POPULATION-DYNAMICS IN WESTERN LAKE ERIE - REGULATION BY FOODLIMITATION AND YELLOW PERCH PREDATION, Journal of Great Lakes research, 20(3), 1994, pp. 537-545
Two Daphnia species exhibited similar dynamic patterns in western Lake
Erie. Populations peaked in early summer, declined to minimum abundan
ce in mid-July, and then disappeared after August. To determine relati
ve importance of food limitation and young-of-year (YOY) fish predatio
n in regulating Daphnia dynamics, we examined relationships (1) betwee
n edible phytoplankton abundances and Daphnia fecundity and birth rate
s, and (2) between Daphnia biomass consumed by YOY yellow perch (Perca
flavescens) and Daphnia death rates. The population peak was created
by a burst of parthenogenetic reproduction. Suppression of birth rates
(<1 individual d-1) by low edible phytoplankton resources (<4 g.m-3 w
et wt) and increased consumption by YOY yellow perch caused a midsumme
r decline of Daphnia populations. Once the Daphnia populations were re
duced, the predation from age-1 and older planktivorous fish in wester
n Lake Erie was likely to keep the populations at low densities in spi
te of increased food resources in late summer. An increased white perc
h (Morone americana) population and the invasion of zebra mussels (Dre
issena polymorpha) in western Lake Erie may alter the cycle of Daphnia
dynamics, hence influencing yellow perch population in the lake.