Protozoa cultivating method for Asian seabass larvae using vegetables and dry fish powder

Abstract

Seed production of marine finfish in Malaysia is still facing problem particularly live feed for starter diet. Aquaculturists are currently using rotifers of the S or SS type, which have sizes from 100 to 200μm. Early stage larvae of some marine finfish species select feeds less than 100μm. In nature, protozoa are consumed by the early stage of marine finfish larvae. Protozoa is a common term for aquatic microorganisms that has been identified to be suitable live feed, as their body sizes are less than 100μm. However, there are very limited studies regarding protozoa culture methods. Thus, the objective of this study is to examine the density changes of Different Protozoa Species (DPS) using batch and continuous culture methods. Then, Asian seabass larvae were reared using live feeds; rotifers, DPS, and Euplotes encysticus. In batch culture method, DPS and one protozoa species; Euplotes encysticus were cultured for the duration of eight days. The diets for DPS and E.encysticus culture were given only at the first day of experiment. DPS and E.encysticus were continuously cultured for the duration of 11 days in the continuous culture method. Every day, 10%, 20%, and 30% of cultured water was harvested and replaced with new water and diets for DPS and E.encysticus. In Asian seabass larval rearing experiment, four types of live feed; rotifer, DPS, E. encysticus, and mixed (rotifer, DPS, and E. encysticus) were given to larvae from 2 to 10 day-after-hatching. Number of seabass larvae in each group was counted every day and their survival rates were determined. The result of batch culture method showed that three and two days were optimum to produce the highest density (2463 and 1037 ind/mL) for DPS and E.encysticus. Next, the result of continuous culture method showed that 10% and 20% were optimum harvesting amount to produce the highest density of DPS and E.encysticus. The discussion of comparison between batch and continuous culture methods showed that the batch culture was the best method for DPS and continuous culture was the best method for E.encysticus. The recommended live feed for the starter diet of Asian seabass was mixed live feeds which consist of rotifer, DPS, and E.encysticus. In conclusion, batch culture method is recommended method to culture DPS, continuous culture method is recommended for E.encysticus, and mixed live feed is recommended for the larval rearing of Asian seabass.