Feeding History, Parental Stock, and Food Selection in Rainbow Trout

Abstract

AbstractFeeding history and parental stock were manipulated to determine whether they could influence food selection in young trout, Salmo gairdrceri Richardson. After 9 training meals of one food, trout selected that food, the familiar one, when given a choice between it and a novel food. (Most choice situations used high and equal densities of unconcealed foods). Selection of the familiar food occurred with several kinds of non-living food. Trout trained on live prey, however, did not always select the familiar one when botli prey were alive, although they did when both prey were dead. Some characteristics of the training effect were investigated. As they became satiated, trout consumed relatively more of the novel food. Duration of food deprivation before a choice test did not change the degree of selection for the familiar food. In addition to eating more of the familiar food, trout struck but rejected relatively more of the novel food. Individual trout trained on two foods ate them in proportions which were characteristic for an individual. After they had learned to select one food, trout were given further training on one of the following: the familiar food, a novel food, or both. Further training on the familiar food did not change the proportion selected. Trout trained on one food for 12 meals and then on a second food for 12 meals selected the second food when given a choice. When the initial training was followed by continuous feeding of both familiar and novel food, trout continued to select the familiar food for 14 to 23 meals. All results suggested that effects of such feeding history would not greatly influence food selection in natural situations. Progeny of different parental stocks were tested to determine whether parental food can influence food selected by offspring. Eggs from trout which ate different kinds of food were hatched in the laboratory. For their first meal, trout were given choices of the kinds of food eaten by the parental stocks. In three main experiments, the young trout did not select the type of food commonly eaten by their parents.