W.A. Bray, A.L.Lawrence-1998
Aquaculture, 159: 275-282
Abstract:
Penaeus monodon post-larvae of Malaysian origin (n=200) were cultured to adulthood (average weight, 90.2 g males, 125.8 g females) with the final six months of growout conducted at salinity ranging from 38-52 ppt. Upon transfer from a hypersaline earthen pond to an indoor maturation 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, respectively. Adults were acclimated to oceanic salinity (35 ppt) in a laboratory recirculating seawater system 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 evaluation of sperm indicated all females (n=20) had mated under the hypersaline pond conditions prior to transfer to the laboratory. Sperm appeared morphologically normal. After three to four weeks of exposure to oceanic salinity under laboratory conditions, strong brown and black markings on the exoskeleton were exhibited by the broodstock, and frequent ovarian development followed. The first female was isolated for spawning five 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 during 98 days of observation. The variable performance among females suggests that there are differential contributions among members of a population to the gene pool, and that culling and replacement of low-producing females in a breeding population can increase nauplii production.
(Shrimp Mariculture Project, Texas Agricultural Experiment Station, Texas A&M University System, 1300 Port Street, Port Aransas, TX 78373, USA)