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 degr ees C, 20 degrees C, 25 degrees C and room temperature) and six storage dur ations (6, 12, 24, 48, 72 and 96 h) on pre-settlement larvae of Crassostrea iredalei indicated that settlement rate deteriorated with time for all tem peratures. The highest settlement rate (40.1%) was attained at a storage te mperature 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 degr ees C and 20 degrees C for 12 to 24 h (21.1-28.2%). Average sets obtained f or storage between 10 degrees C and 20 degrees C was 16.6-19.7% for up to 4 8 h, and sets for room temperature (ca. 30 degrees C) and 5 degrees C for 1 2 h were 11.9% and 16.9%, respectively; whereas at 25 degrees C the set rat e was 10.7% for 6 h. Storage at all other levels of temperature and duratio n resulted in poor set rates of less than 8%. All successfully set larvae f rom this experiment were further kept in the hatchery for three weeks to ob serve their short-term post-settlement survival. Survival rates were closel y related to the setting rates, whereby higher sets contributed to better s urvival rates. The highest survival rates, 61.3-84.8%,were recorded for lar vae set at temperatures ranging from 10 degrees C to 20 degrees C with a st orage 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 tota l 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.