Diet Composition of Wild Brown Trout and Stocked Rainbow Trout in a Coldwater Tailwater Fishery in North Georgia

The Lanier Tailwater section of the Chattahoochee River, Georgia, below Buford Dam has populations of wild brown trout (Salmo trutta) and stocked rainbow trout (Oncorhynchus mykiss). To better understand the ability of wild brown trout to recruit to the fishery, stomach contents of brown trout and rainbow trout were examined in summer and fall 2011 and winter and spring 2012 at four locations along the river. Midges (Diptera) were the most common category observed in the diets of both species throughout the study. Other common items included caddisflies (Trichoptera), stoneflies (Plecoptera), ants/termites (Formicidae/Termitoidae), worms (Annelida), and scuds (Isopoda). While rainbow trout were more likely than brown trout to have empty stomachs, their diets were otherwise similar. Midges were consumed more often by brown trout and rainbow trout than any other diet category at all sites and in all seasons. Some categories were less prevalent at the most upstream site. Stoneflies were most common and caddisflies were least common in diets of both species in winter compared to the other seasons. Terrestrial insects were most commonly consumed in summer. Although diet composition of brown trout showed little ontogenetic shifts, size of brown trout appeared to have an influence on feeding habits as larger fish were more likely to have empty stomachs. There may have been a greater occurrence of piscivory, particularly in larger brown trout, than the results of this study indicated.

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