(Sperm production and fertilization test in rainbow trout, Salmo irideus Gibbons, during the first reproductive cicle.)

Abstract

At Fishery Station of Campos do Jordão, São Paulo State, Brazil, an experiment was carried out for to investigate the sperm production and fertilization capacity of sperm of rainbow trout, Salmo irideus Gibbons, during the first-reproductive cycle. The spawning season extended from May to September. Production increased from beginning to mid-season, followed by a gradual decline. The average values of semen volume, sperm concentration and total sperm concentration, obtained from every 2 weeks collections from 55 males were: 8.42 ml; 9.25 sperm x 10⁶/mm³and 91.49 x 10⁹ sperm/ml, respectively. The regression analysis showed third degree curves, for sperm volume and sperm concentration, while the total production of sperm followed a decreasing equation (P < 0.01). These characteristics were independent of the body weight. The fertility estimation revealed significance for the quadratic effects of the incubated number of eggs and subjective direct motility (P < 0.01), and the cubic effects of the numbers of embryonic eggs and the numbers of live sperm per mm³ x 10⁶/egg (P < 0.05). The respective means were: 145.92; 91.88; 62.14 and 18.69.