Growth and survival of the blacklip pearl oyster Pinctada margaritifera (Linnaeus) spat reared with various combinations of microalgae in different stocking densities

The present study has revealed that, the temperature has a crucial role among the observed physiochemical parameters on the growth and survival of P. margaritifera spat. Instantaneous growth rates (IGRs) in DVM, APM and TWT were calculated and used to assess the variation in growth of spat reared with different feed mixtures (FM-1 8) of five diatoms and stocking densities (SD-10, 20 and 30). Among all treatments, FM-3, 4 and 5 gave better performance than that all other combinations of diatoms. Chaetoceros calcitrans, Nannochloropsis oculata and Chlorella marina was formed major shares (60%) respectively in combination with 10% each of rest of algae. FM-7 which had all diatoms in equal (20%) measure performed as the next best feed combination. Poor growth was observed in spat fed with FM-2 which was dominated by Isochrysis galbana (60%) and FM-6 which comprised of an equal measure (30%) of Pavlova salina, Isochrysis galbana, Chaetoceros calcitrans and Nannochloropsis oculata and Chlorella marina at 5% each. When the stocking density increases (SD–20 and 30) growth rates (IGRs) in all three variables decreased irrespective of feed combinations. Mortality rates varied in different treatments and also with stocking densities. Maximum mortality was observed in control (FM -8) in all the stocking densities. However, in all the feeding combinations and stocking densities, 100 % survival was observed upto the 9th DOC and mean cumulative mortalities showed a gradual increase. Comparatively very less cumulative mortality and better growth performance were recorded in stocking density, SD-10. Available online at: www.mbai.org.in doi: 10.6024/jmbai.2014.56.2.01779-01