Nutritional Deprivation after Stocking as a Possible Mechanism Leading to Mortality in Stream-Stocked Brook Trout

The low survival rate of hatchery brook trout (Salvelinus fontinalis) stocked in the wild may be due to their inability to obtain sufficient food for survival. A comparative analysis of the diet of catchable-sized resident brown trout (Salmo trutta) and stocked brook trout was carried out on McMichael Creek, Monroe County, Pennsylvania to determine if there is a differential success in feeding which might affect mortality. Three hundred resident brown trout and stocked brook trout were collected over a 2-year period (1979-1980). The number of organisms in the stomach and the total volume of its contents was determined for each fish. Overall condition was checked prior to stocking and following capture of the trout. The condition of hatchery trout declined steadily following their release into the wild. The rate of this decline generally increased for those stocks with high, average condition factors prior to stocking. Resident trout maintained a stable overall condition throughout the study period. Wild brown trout were twice as successful in feeding as domestic brook trout but few differences occurred in types of prey consumed by the two species of trout. Both species of trout exhibited great diversity in their forage selection. The resident population, however, indicated a greater flexibility in switching to alternate food items as they became available for consumption.