Predation On Stocked Rainbow Trout By Chain Pickerel And Largemouth Bass In Lake Ouachita, Arkansas

In many reservoirs predation on stocked fish has been considered as one of the major limiting factors in establishing a particular population. Following several years of water quality determinations it was found that Lake Ouachita maintained a sufficiently oxygenated hypolimnion to support trout. As a result several thousand catchable rainbow trout, Salmo gairdneri, were stocked into the lake. The results of this attempt to establish a trout fishery have been disappointing for a combination of reasons; however, while collectint for brookstock chain pickerel, Esox niger, and from fisherman reports, it became evident that predation on the stocked trout must be very high. Collections of largemouth bass, Micropterus salmoides, and chain pickerel were made with a boom-type electro-shocker during January and February, 1970. Sampling was done at night within an approximate 100-acre area adjacent to a trout stocking point. Two separate areas were collected and collections were made the date on which trout were stocked, one day after stocking, two days after stocking, and eight days after stocking. During the collecting period a total of 14,840 nine inch trout were stocked in the two collecting areas. Eighty-six (86) largemouth bass, weighing 162.9 pounds and twenty-four (24) chain pickerel, weighing 33.1 pounds, were collected for stomach analysis. The smallest size bass containing trout in its stomach was sixteen (16) inches total length. The smallest chain pickerel in which a trout was found was fifteen (15) inches in length. Of all chain pickerel, fifteen inches and over, 54.5% has trout in their stomachs and 48.6% of the largemouth bass, sixteen inches aqd longer, contained trout. One hundred percent of the chain pickerel, nineteen inches or larger, and ten of the eleven bass, eighteen inches or larger, contained trout. Although the size trout stocked during these collections averaged nine inches in length, 79.6% of the trout consumed were eight inches or less. No trout over nine and one-half inches was found in bass or pickerel stomachs; however, two or more trout per stomach was common and five was the maximum number of trout found in one stomach.

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