Production and storage of sperm from the black sea bass Centropristis striata L

Black sea bass Centropristis striata L. are protogynous hermaphrodites that develop and spawn as females before changing sex to male. Since all fish eventually become males, determining the relationship between sperm production, sperm quality and seasonal changes in plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) could be useful for identifying appropriate males to maintain as broodstock. Milt and blood samples were collected three times during an 8-week spawning season. Milt volume (3.5 +/- 0.76 mL kg(-1)), sperm density (3.2 x 10(8) +/- 0.31 cells mL(-1)), sperm production [11 x 10(8) +/- 3.4 cells kg(-1) body weight (BW)] and sperm motility (80 +/- 0.6%) were at their highest during the first sampling interval and coincided with the highest 11-KT levels (1.0 +/- 0.11 ng mL(-1)). All of the sperm indices decreased to their lowest levels during the final 3 weeks of the study. Sperm viability was highly correlated (adjusted R2 = 0.84) with sperm motility. Sperm cryopreserved in modified Mounib's extender (MME) had the highest post-thaw motility compared with two other extenders. Post-thaw motility of sperm cryopreserved in MME was not different from fresh after 90 days of storage. There was no difference in fertilization rates between fresh (69 +/- 2.4%) and post-thaw (67 +/- 4.1%) sperm samples taken from the same male or among males. These results demonstrate that the quality of black sea bass spermatozoa is higher earlier in the spawning season and that acceptable post-thaw fertilization rates can be obtained from cryopreserved sperm.