Publication Abstract

Pheromone-induced spawning of Pacificherring. 2. plasma steroids distinctive to fish responsive to spawning pheromone

J. Carolsfeld, A.P. Scott and N.M. Sherwood

Aspawning pheromone in the milt (semen) and testes of the Pacific herring, Clupea harenguspallasi, is thought to facilitate school spawning of this species. We found thatresponsiveness to the spawning pheromone was variable among ripe fish (milt-producing orovulated). Measurement of five principle reproductive steroids in the free form and fivesteroids in conjugated forms in the plasma of male fish early in the spawning season(newly ripe fish) showed that elevated plasma levels of 3α,17β-dihydroxy-5β-pregnan- 20-one and 17α hydroxyprogesterone coincided with responsiveness to the spawningpheromone in these fish; levels of other steroids did not differ. In contrast,responsiveness to the pheromone by female fish later in the spawning season(ripe-and-holding fish) coincided with lower levels of glucuronated 17α,20β-dihydroxyprogesterone and a lowergonadosomatic index. We suggest that these differences indicate a more advanced maturereproductive state in the responsive individuals among both the newly ripe male and theripe-and-holding female fish. We found no differences in the level of cortisol in theblood of the herring that could be correlated with differences in pheromonalresponsiveness. We conclude that differences in responsiveness to the spawning pheromonecoincide to some extent with levels of reproductive maturation but probably not withrecent stress.

Reference:

J. Carolsfeld, A.P. Scott and N.M. Sherwood, 1997. Pheromone-induced spawning of Pacificherring. 2. plasma steroids distinctive to fish responsive to spawning pheromone. Hormonesand Behavior, 31, 269-276.