Seasonal Analysis of Predator-Prey Size Relationships in West Point Lake, Alabama-Georgia

The relationships between largemouth bass (Micropterus salmoides) length and lengths of bluegill (Lepomis macrochirus) and gizzard shad (Dorosoma cepedianum) consumed by largemouth bass were explored seasonally in West Point Lake during April-November 1981. There were no significant differences in the predator-prey size relationships for largemouth bass and bluegill across seasons; however, there was a significant increase in the size of gizzard shad preyed upon during the fall as compared to earlier in the spring-summer. This seasonal shift was not a normal fall occurrence and likely was caused by a 4.2-m drop in the summer lake level which increased crowding of predator and prey and enhanced the predatory effect of largemouth bass on gizzard shad. Analysis of the relative abundance of prey species over a 7-year period (1975-1981) showed that in 1977, 2 years after impoundment, bluegill and gizzard shad were the dominant prey species. By 1981, bluegill had declined in abundance and the gizzard shad population was composed primarily of large, adult individuals; threadfin shad (Dorosoma petenensei had increased tenfold in abundance and were a major component of the diet of small and intermediate size (<300 mm) largemouth bass.

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