15 MARCH 1999
HATCHERY REARING OF THE TROPICAL BLACKLIP OYSTER SACCOSTREA ECHINATA (QUOY AND GAIMARD)
O.C. Southgate, P.S. Lee-1998
Aquaculture, 169 (3-4) : 275-281 (Current Contents)
Abstract:
This paper reports on two growth trials in which larvae of the tropical black-lip oyster, Saccostrea echinata (Quoy and Gaimard), were reared to settlement, and on early spat growth to 2 weeks post-settlement. Broodstock oysters were induced to spawn by increasing water temperature to 33 degrees C followed by rapid reduction in salinity and water temperature. Female oysters spawned a mean of 8.0 x 10(6) and 9.4 x 10(6) eggs in the first and second spawning, respectively. The maximum number of eggs spawned per individual was 18 x 10(6). Mean egg diameter was 52.9 +/- 3.2 mu m (+/- s.d. n = 30) and 55.2 +/- 2.8 mu m (n = 50) in the first and second spawning, respectively. Larvae reared at 28-31.2 degrees C and fed an algal diet consisting of Isochrysis sp. (clone T-ISO), Pavlova salina and Chaetoceros muelleri reached settlement 20 days after-fertilisation. However, larvae reared at 27-30 degrees C and fed only T-ISO and P. salina developed more slowly and did not reach settlement until 25 days after fertilisation. Survival from D-stage to competent pediveliger stage was low and ranged from 4.2-5.2%. At 2 weeks post-settlement, spat had a mean shell length of 2.3 +/- 0.4 mm and a mean dry weight of 1.7 +/- 0.2 mg. Although S. echinata seed can successfully be reared in the hatchery, poor larval survival may limit the potential of this species to support a hatchery-based aquaculture industry.
(James Cook Univ N Queensland, Dept Aquaculture, Townsville, Qld 4811, Australia, e-mail: paul.southgate@jcu.edu.au)