AVOIDANCE OF A PUTATIVE PHEROMONE, 17-ALPHA,20-BETA-DIHYDROXY-4-PREGNENE-3-ONE, BY PRECOCIOUSLY MATURE CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA)

To test the hypothesis that the gonadal steroid, 17 alpha,20 beta-dihy droxy-4-pregnene-3-one (17 alpha,20 beta-P) acts as a pheromone for ma ture male salmon, we examined the behavioral responses of precociously mature chinook salmon (Oncorhynchus tshawytscha) to this odorant. The se males avoided water scented with 17 alpha,20 beta-P in a two-choice maze. This avoidance response was not shown by immature chinook salmo n of the same age or by mature males to a second steroid hormone, test osterone. Taken together, these results suggest that 17 alpha,20 beta- P is a behaviorally relevant odorant for precociously mature male salm on. The avoidance response observed may reflect the sneaker spawning t actic employed by precociously mature fish, as attraction to the odora nt was predicted for mature males in general.