Both ovarian fluid and female urine increase sex steroid hormone levels in mature Atlantic salmon (Salmo salar) male parr.

We compared the ability of urine and ovarian fluid from female Atlantic salmon (Salmo salar) to stimulate increase in plasma concentrations of sex steroid hormones in mature conspecific male parr (priming effect of the stimuli). We also tested the hypothesis that prostaglandin F2alpha (PGF2alpha) may act as a priming pheromone in the tested stimulants. Individual males of salmon parr were exposed to female urine, ovarian fluid, urine-ovarian fluid mix, or PGF2alpha. Plasma concentrations of the sex steroids of 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) were higher in males exposed to urine, ovarian fluids, and PGF2alpha compared to control males. PGF2alpha and a mixture of urine and ovarian fluid also gave increased concentrations of 11-ketotestosterone (11-KT). Concentrations of PGF2alpha were higher in ovarian fluids than in urine. A behavior test with mature male parr in a fluviarium showed neither attraction to nor avoidance of 0.1 nM PGF2alpha, but plasma levels of 17,20beta-P were significantly higher in exposed males compared to controls.