The body length and width of Proales similis (mean±SD; 83±11 μm and 40±6 μm, respectively) is 38.1% smaller and 60.3% narrower than that of Brachionus rotundiformis.Due to its small size, P. similis has potential for rearing marine fish larvae which require first food smaller than B. rotundiformis. We examined the feasibility of using P. similis as live food by analyzing its life history, population growth and feeding incidence by fish larvae. P. similis produced first offspring on 2.5-2.8 days after hatch. Females produced 4.3-7.8 offspring during their 2.9-3.4 day reproductive period. P. similis grew well at temperatures 25 to 35 0 C (density = 250 to 1030 ind./ml; r = 0.68 to 0.81 day -1 ) and at salinities 2 to 15 ppt (density = 360 to 500 ind./ml; r = 0.73 to 0.78 day -1 ). Population density of P. similis was higher than B. rotundiformis after 8 days of culture period with either N. oculata and C. vulgaris as food. In mass culture, population density of P. similis increased from 25 to 2,400 ind./ml (r = 0.42 day -1 ) after 11 days. Results from feeding experiments confirm that P. similis is consumed by seven-band grouper (Epinephelus septemfasciatus) larvae. The larvae demonstrated the highest feeding rate at 20 ind./ml of P.similis.

17The SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish Cheilinus undulatus showed that it is an excellent starter food for these species because of their 34 high selectivity index and improved survival. In addition, P. similis was ingested by Japanese 35eel Anguilla japonica larvae with complicated digestive system. The use of P. similis as starter 36 feed for small mouth fish larvae is highly recommended. 37Keywords 38 3 euryhaline rotifer, larval rearing, live food, small-mouth fish, Proales

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