A COMPARATIVE STUDY ON THE EFFECT OF USING COPEPOD (Parvocalanus crassirostris) NAUPLII AND ROTIFERS AS INITIAL LIVE FEED ORGANISM ON THE SURVIVAL RATE OF GROUPER (Epinephelus polyphekadion) LARVAE.  

The culture of high-valued marine fish (such as grouper) has been expanding in Asia and the current demand for live grouper commands a lucrative wholesale price.  In SE Asia, groupers have been cultured for over 30 years. However, current culture methods still face very low hatchery survival in some of the most commercially important species largely due to inadequate larval feed items. A study was conducted to evaluate the potential of improving grouper larvae production by comparing the effects of feeding them with copepod nauplii and rotifers during their early stage of larval development.

Six 200L tanks where stocked with newly hatched grouper larvae at a density of 30 larvae per liter. Three tanks were fed with newly hatched copepod nauplii at a density of 5 nauplii per ml while the other 3 tanks were fed with s-type rotifers at density of 10 rotifers per ml.  The feeding trial was started when the larvae reached the age of 2 days post hatching. Green microalgae (Nannochloropsis sp.) was added into the rearing water every day at the density of 200,000 cells per ml to nourish the live feed organisms. The experiment was terminated after 7 days and remaining larvae were counted to determine the survival rate.  Data analysis using T-test revealed that grouper larvae fed with copepod nauplii have significantly higher survival rate of 64.25 ± 2.81% compared to those that were fed with rotifers which was only 7.13 ± 3.69 %.  This higher survival rate may have been influenced by the presence of higher number of prey inside the gut of the larvae samples that were collected one day after the onset of feeding.  Almost 100% of the larvae in tanks fed with copepod nauplii have their guts containing prey with average of 4.46 ±0.50 nauplii per larvae while in tanks fed with rotifers, only 20% of the larvae were able to ingest their prey  with an average 0.6 ± 0.69 rotifers per larvae.