Ivasauskas, T.J., and P.W. Bettoli. 2012. Dispersal, mortality, and predation on recently-stocked rainbow trout in a Tennessee reservoir. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 65(2011): 83-91.
Abstract
Hatchery-raised rainbow trout Onychorhynchus mykiss (n = 44; mean total length = 235 mm) were implanted with ultrasonic tags and stocked into Dale Hollow Lake, Tennessee, on 7 January and 6 March 2009. Fish were tracked at least once per week for eight weeks to describe post-stocking dispersal rates, movements, and habitat use. Dispersal and movement followed a 3-stanza pattern characterized by rapid movement away from each stocking site during the first week, relatively little movement during the next three weeks, and a resumption of large movements during the final four weeks that fish were tracked. Rainbow trout exhibited a strong affinity for coves and were rarely encountered in the main channel. Tagged trout stocked in March exhibited lower mortality (Zweekly = 0.027) than those stocked in January (Zweekly = 0.062) during the first eight weeks post-stocking. Diets of potential predators in Dale Hollow Lake and two other Tennessee reservoirs were examined. Walleye Sander vitreus , smallmouth bass Micropterus dolomieu, largemouth bass M. salmoides, spotted bass M. punctulatus and holdover rainbow trout all preyed on recently stocked rainbow trout. Smallmouth bass and walleye differentially consumed smaller rainbow trout and the probability of consuming a trout was positively related to predator size. Walleye were more likely to feed during January than March. Mortality of trout due to walleye predation over the first eight weeks post-stocking was estimated to be 2.2 to 2.9 times higher for fish stocked in January than for fish stocked in March.