Patterns of feeding of the bluegill sunfish, Lepomis macrochirus (Rafinesque), in two heated reservoirs of Texas

Abstract

The feeding patterns of bluegills, Lepomis macrochirus(Rafinesque), were studied in Lake Nasworthy and Lake Bastrop, reservoirs providing cooling waters for power generating plants. Fish were collected with a 10-foot otter trawl on alternate months between April 1968 and June 1969 from two sections in each reservoir: one station was in the discharge canal and the other in the open water, far removed from the discharge-area. Sampling was continued for 24 hours in each reservoir during each collection trip, and fish were taken on alternate hours from each station. The two reservoirs were sampled within 15 days of each other. A total of 1366 specimens from the two reservoirs were examined by the points method of stomach analysis. The data were analyzed from the following points of view: 1) general comparison of feeding in the two reservoirs, 2) size of fish and feeding, 3) time of day and feeding, 4) season of year and feeding, and 5) types of stations and feeding. Pertinent interactions were also evaluated. Comparisons were based on average index of fullness of the stomach and average food points per fish, as well as on food categories. The percentage of fish with empty stomachs was very low in both reservoirs (about 4 percent in Lake Nasworthy and 2 percent in Lake Bastrop). The average index of fullness of the stomachs was somewhat higher for Bastrop than for Nasworthy bluegills. The average food points per fish differed little between the reservoirs..