Performance of Used Synthetic Seawater on Growth and Survival of Larvae of Macrobrachium Rosenbergii

Abstract

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A study was conducted to explore the feasibility of reuse of used synthetic seawater for larviculture of Macrobrachium rosenbergii in closed recirculation and static flow-through systems. In closed recirculation system, larvae of M. rosenbergii were reared in rectangular cement concrete tanks of capacity 1000 L with attached biofilter chamber containing molluscan shells as biofilter media. In static flow-through system, the larvae were reared in conico-cylindrical shaped FRP tanks of capacity 300 L and the culture water were exchanged @ 15-20% daily. In both the rearing systems, newly prepared synthetic seawater was used in the first cycle. At the end of first cycle, the culture water was reconditioned for 8-10 days using vigorous aeration and recirculation through a biofilter in a separate tank and subsequently re-used in the second and third cycles also. In both the types of rearing systems, larvae were stocked @ 100 per litre and reared till 90% of larvae metamorphosed into post-larvae. In both the systems, crucial water quality parameters like ammonia nitrogen (NH +-N) and nitrite nitrogen (NO2-N) were within the acceptable limits. In recirculatory system, the survival of larvae of M. rosenbergii was 47.95, 47.00, and 46.09% in the first, second and third cycles respectively and the larval rearing period varied from 35 to 37 days. Whereas, in static flow-through system the respective values were 45.3, 44.15, and 42.98%. The larval rearing period varied from 34 to 40 days. No significant difference in the rate of metamorphosis was observed in new and used synthetic seawater.