Time study of coronary myointimal hyperplasia in precocious male steelhead trout, Salmo gairdneri.

Time-related observations of myointimal hyperplasia in precocious male steelhead trout maintained in the laboratory suggest that regression of arterial lesions occurs. The most severe myointimal hyperplasia in these trout was observed from June through August during which time the mean lesion rank of the sampled fish reached 2.3 on a ranking scale of 0-5. This time is concomitant with the period of increasing gonadal mass in the strain studied. However, there was no correlation between gonad size and arteriosclerotic lesion severity. Mean lesion severity of fish examined from September through November was approximately one-half that reported for the previous periods. During the September-November period gonadal weights in this strain of fish decreased. Although no statistical correlations could be derived it is suggested that in steelhead trout, changes in myointimal hyperplasia lesion severity are associated with changing reproductive patterns.