Effects of storage temperature and duration on the setting and post-set spat survival of the tropical oyster, Crassostrea iredalei (Faustino)

The effects of six storage temperatures (5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C and room temperature) and six storage durations (6, 12, 24, 48, 72 and 96 h) on pre-settlement larvae of Crassostrea iredalei indicated that settlement rate deteriorated with time for all temperatures. The highest settlement rate (40.1%) was attained at a storage temperature of 20 degrees C for 6 h. This was followed by 10 degrees C and 15 degrees C for 6 h, with mean percent sets of 35.4% and 33.5%, respectively. An above-average set of 29.5% was obtained for the control larvae (larvae directly from the rearing tanks) compared to larvae stored between 10 degrees C and 20 degrees C for 12 to 24 h (21.1-28.2%). Average sets obtained for storage between 10 degrees C and 20 degrees C was 16.6-19.7% for up to 48 h, and sets for room temperature (ca. 30 degrees C) and 5 degrees C for 12 h were 11.9% and 16.9%, respectively; whereas at 25 degrees C the set rate was 10.7% for 6 h. Storage at all other levels of temperature and duration resulted in poor set rates of less than 8%. All successfully set larvae from this experiment were further kept in the hatchery for three weeks to observe their short-term post-settlement survival. Survival rates were closely related to the setting rates, whereby higher sets contributed to better survival rates. The highest survival rates, 61.3-84.8%,were recorded for larvae set at temperatures ranging from 10 degrees C to 20 degrees C with a storage time of up to 48 h. These levels were comparable to the control (68.0%) and 5 degrees C for up to 12 h (68.9%). Storage at 72 h resulted in total mortality at all temperatures, except for those stored at of 10 degrees C (51.5% survival) and 20 degrees C (14.7%). (C) 2000 Elsevier Science B.V. All rights reserved.