ABSTRACT
The production of sex-reversed trout benefits the aquaculture industry allowing “all female” populations to be obtained. Females become sexually mature 1 year later than males, reaching their marketable size before maturation. Therefore, the production of entire female populations reports important economical benefits in commercial rainbow trout culture [1]. Sex-reversed rainbow trout have similar external morphology to normal males but lack sperm ducts [2], meaning that the animals must be sacrificed to obtain the milt. The peculiarities of the sperm, obtained directly from the testicle, make necessary the development of a specific cryopreservation protocol. Spermatozoa of sex-reversed females are immotile when collected from the testicle and need exogenous maturation before activation. General characteristic of sperm are significantly different from those of ejaculated milt (Table 1). The lack of sperm ducts makes it necessary to maintain a high number of animals in fish farms, since they must be killed to obtain their sperm. Therefore, cryopreserving the sperm of these individuals appears to be of great use since it would make sperm available all year round, reducing the need for a large male stock, and facilitate artificial fertilization using the milt of the same male in different breeding periods.
