SUCCESSFUL REPRODUCTION OF PENAEUS-MONODON FOLLOWING HYPERSALINE CULTURE

Penaeus monodon post-larvae of Malaysian origin (n = 200) were culture d to adulthood (average weight, 90.2 g males, 125.8 g females) with th e final six months of growout conducted at salinity ranging from 38-52 ppt. Upon transfer from a hypersaline earthen pond to an indoor matur ation laboratory, broodstock were drab olive in color and exhibited no ovarian development even though growth had averaged 2.5 g/week and 3. 9 g/week for males and females, respec tively. Adults were acclimated to oceanic salinity (35 ppt) in a laboratory recirculating seawater sy stem and unilaterally eyestalk ablated after two days. For two weeks, all shed exoskeletons of females were dissected to determine presence of spermatophores. Results of dissections and light microscope evaluat ion of sperm indicated all females (n = 20) had mated under the hypers aline pond conditions prior to transfer to the laboratory. Sperm appea red morphologically normal. After three to four weeks of exposure to o ceanic salinity under laboratory conditions, strong brown and black ma rkings on the exoskeleton were exhibited by the broodstock, and freque nt ovarian development followed. The first female was isolated for spa wning five weeks after eyestalk ablation, and a high frequency of spaw ning was achieved beginning 6-8 weeks after eyestalk ablation. In the final six weeks of observation, an average of 7.6% to 9.0% of females; spawned nightly. Mean number of eggs per spawn was 315,000 +/- 28,920 (s.e.), with 195,000 +/- 24,400 nauplii per spawn and 59.6% hatch (n = 60). Of significance, it was observed that 20% of females produced 67 .7% of total nauplii production and 30% either died or did not spawn d uring 98 days of observation. The variable performance among females s uggests that there are differential contributions among members of a p opulation to the gene pool, and that culling and replacement of low-pr oducing females in a breeding population can increase nauplii producti on. (C) 1998 Published by Elsevier Science B.V.