Influence of Social Rank and Size on Thermoselection Behavior of Bluegill (Lepomis macrochirus)

Abstract

Juvenile bluegill (Lepomis macrochirus) (95–110 mm TL) were given a choice between an environment at their preferred temperature (31.0 C) plus a social dominant (130–160 mm TL) or an environment either cooler (27.0 C) or warmer (34.0 C) than their preferred temperature, but without a large bluegill. During a 3-day control period, when 20 small fish were isolated in individual experimental aquaria, each spent more than 75% of its time at 31.0 C rather than warmer or cooler temperatures. After an adult was placed into the preferred temperature side of each aquaria, small fish spent nearly the entire 3-day experimental period at previously non-preferred temperatures on the side without the larger bluegill. No significant correlation (r = −0.03) was found between length and selected temperatures of 35 individual bluegill (70–140 mm) tested in a temporal temperature gradient.