The predatory response of Lepomis gibbosus to size and color among Chaoborus prey.

Abstract

Biotic interactions such as predation influence the structure of freshwater communities. The predator-prey relationship between fish and zooplankton is one such interaction which has been widely studied. Size and color differences among prey items have been well documented as factors influencing predation. The purpose of our study was to examine the effects of size and color variability of zooplankton prey on the predatory response of fish. In order to study these relationships, we sued pumpkinseed (Lepomis gibbosus) and two zooplankton species which differed in size: Chaoborus punctipennis from Douglas Lake, Cheboygan County, Michigan, and Chaoborus flavicans from Lancaster Lake, Cheboygan County, Michigan. We dyed the Chaoborus species with Rotamin B in order to examine the effects of color. We measured the response times of the pumpkinseed to four individual prey types: large uncolored, large colored, small uncolored, and small colored. We also conducted six sets of selectivity trials in which the fish were given a choice between two Chaoborus types. The mean response times were compared using t-tests, and the results of the choice experiments were analyzed using X2 goodness-of-fit. We found, as expected, that pumpkinseed predatory response increases as size and pigmentation of prey increases. An understanding of how these predators affect the population composition of the zooplankton may give us much insight into the structure of freshwater communities.