Cryopreservation of sperm in marine fish

Since the first work of Blaxter in 1953, fish sperm cryopreservation has be en attempted on about 30 marine species. The present paper reviews the tech niques used and the results published in these species. Particular attentio n is paid to the handling procedure of sperm before freezing, the problems of semen ageing and semen contamination with urine. The quality of frozen-t hawed semen was evaluated using previously standardized biotests, such as a two-step motility activation technique adapted for the different species a nd fertilization assays using a discriminating insemination technique. Most extenders used in marine fish are saline or sugar solutions. From the inve stigated cryoprotectants, dimethyl sulphoxide (DMSO) generally leads to the best results. Cooling rates range from 8 degrees C to 99 degrees C min(-1) ; the thawing rate is generally high. Compared with freshwater species, a h igh percentage of spermatozoa survives cryopreservation. Therefore, and bec ause of the simplicity of the techniques, the cryopreservation of marine fi sh sperm is suited for application in aquaculture.