Thyroid Activation of Olfactory Imprinting in Coho Salmon

Abstract

From the work reviewed here (Chap. 3), we formulated the hypothesis that olfactory imprinting is facilitated by increases in levels of thyroid hormones at the time of smolt transformation (Scholz 1980). Our overall plan for testing this hypothesis was to inject TSH or ACTH into pre-smolt coho salmon while simultaneously exposing them to a synthetic chemical, either morpholine or phenethyl alcohol. Ten months later behavioral tests were performed to determine if the fish had retained a long-term olfactory memory of the odor to which they had been exposed at the time of hormone treatment. Although this experiment is simple conceptually, it proved to be difficult to perform because of the controls that were required. In performing this set of experiments we had three major objectives: