CRYOPRESERVATION OF BLUE CATFISH SPERMATOZOA AND SUBSEQUENT FERTILIZATION OF CHANNEL CATFISH EGGS

Successful cryopreservation of fish spermatozoa has important implicat ions for genomic conservation and for aquaculture. We report the first long term cryopreservation of ictalurid sperm. Spermatozoa from nine blue catfish Ictalurus furcatus were cryopreserved for 12 months in th ree concentrations (3.75 X 10(8), 1.50 X 10(9), and 6.00 X 10(9) sperm atozoa per straw), within two different straw sizes (0.5 and 1.0 mL), and with two cryoprotectants (DMSO or methanol combined with powdered skim milk). Cryopreserved spermatozoa were then used to fertilize lots of 450 eggs of channel catfish Ictalurus punctatus. Mean relative fer tilization percentage for sperm treated with DMSO was 32% (range of 23 -54%) of the fresh control. Spermatozoa frozen with the combination of an intracellular cryoprotectant (methanol) and an extracellular cryop rotectant (skim milk) produced no fertilization. No difference (P > 0. 05) was observed between fertilization percentage of spermatozoa froze n in the two straw sizes. The highest level of relative fertilization percentage (54%) was achieved with the highest insemination dose, 6.00 X 10(9) spermatozoa per straw (P < 0.05). There was no difference (P > 0.05) in fertilization percentage between insemination doses of 3.75 X 10(8) and 1.50 X 10(9) spermatozoa per straw. Cryopreservation of b lue catfish spermatozoa can be optimized by using the high concentrati on of sperm (6.00 X 10(9)) and DMSO as cryoprotectant in either 0.5- o r 1.0-mL straws.