Martinez, E., Scarpa, J., Laramore, R.
Abstract:
Hatcheries raising penaeid shrimp have encountered high mortality
during ear1y larval stages. In order to maximize survival of
developing larvae during the hatchery stage, larvae should be reared
close to optimal conditions. One environmental parameter that has a
profound effect on survival is temperature. Seven laboratory
experiments were conducted to determine an optimum temperature
for the hatching and rearing to protozoea II (ZII) of the commercially
important shrimp, Penaeus vannamei.
Broodstock animals were SPF second generation Mexican P.
vannamei. Mated females with well placed spermatophores were
collected and placed in individual spawning tanks. Once eggs were
observed in the water column, eggs were removed by siphon and
passed through a large volume sieve. Three 5 mL aliquots were taken
to determine eggs density. Temperatures tested ranged from 25-35 C
in 2 C increments. Eggs were placed in 4L jars with a water salinity
of 32-33 ppt. In each trial, each container received 1500 eggs from a
single spawn. Approximately 48 hours after fertilization each
container was inoculated with the diatom Thalassiosira weissflogii to
give a final density of 20,000 cells/mL. At this time nauplii were
metamorphosing into the zoeal stage.
Hatch percentages varied between experiments but followed a general
trend of being lowest at the tested temperature extremes. Survival to
ZII varied between experiments but also followed a general trend of
being lowest at the tested temperature extremes. In one experiment,
the time at which 60% of the anima1s had entered the naupliar 5 (N5)
stage was determined. As temperature increased time to the NS stage
decreased dramatically (e.g., 44 hr at 29 C versus 34 hr at 31 C).
Overall, it was determined that 29 C was the optimal temperature of
rearing P. vannamei from egg to protozoea II. This temperature had
the highest hatching success and survival although it did not have the
fastest rate of development. Higher temperature caused faster
development to protozoea II but with a concomitant increase in the
proportion deformed and a decrease in survival.
(Harbor Branch Oceanographic Institution, Inc., 5600 U.S. 1 North
Ft. Pierce, FL 34946 USA)