Abstract
Predation of eggs and larvae of bluegill (Lepomis macrochirus), by snails (Semisulcospira spp.and Sinotaia quadrata histrica) were examined during the bluegill reproductive period (July and August) in 2003 and 2005. At a littoral study site in the northern basin of Lake Biwa, population densities of snails were significantly higher in bluegill nests than in their surroundings, indicating deliberate aggregation of the former. Laboratory experiments to assess the degree of predation on bluegill eggs and larvae by snails showed a significant decrease in egg and larval numbers when established in aquaria together with Semisulcospira spp., and Sinotaia quadrata histrica, respectively. During experimentation, predatory behavior by snails was also directly observed, indicating that snails aggregating in bluegill nests probably predate eggs and larvae despite parental care of the latter.
