The effect of vegetation density on juvenile bluegill diet and growth

Experimental ponds (0.4 ha) were used to evaluate the effects of vegetation density on bluegill (Lepomis macrochirus) diet and growth in the absence of pelagic predation risk. Fish (30-50 mm, total length) were stocked at a rate of 15 kg per pond. By the end of the 3-month experiment, bluegill in the low vegetation treatment (109 gm^-2±21.0 SE, n=4) had grown 20% longer than the fish in the high vegetation treatment (712 gm ^-2±54.3 SE, n=4) despite having similar mean stomach fullness. Bluegill in the high vegetation treatment ingested more gastropods and odonates and less benthic prey (chironomids) than did the fish in the low vegetation treatment. Very little pelagic zooplankton were eaten by fish in either treatment despite the lack of predation risk in the open water habitat. These results suggest that bluegill chose to forage in a vegetated habitat even in the absence of predation risk, resulting in reduced growth.