SAMPLING SHRIMP POPULATIONS IN HATCHERIES

Shrimp populations were estimated with volumetric sampling techniques during different phases of hatchery operations. Factors considered whi ch might effect precision of estimates included stage, age, density an d temperature. Estimates of nauplii were obtained with coefficient of variation values smaller than 3% when nauplii were concentrated in 20- L buckets and smaller than 8% when released in 13,000 L of water in la rval rearing tanks. Ln both cases estimates were of sufficient precisi on to make management decisions for routine hatchery work. A technique was developed for estimating shrimp populations in larval rearing tan ks with coefficient of variation values smaller than 15%. Volumetric s ampling of postlarvae older than PL(4) in larval rearing tanks was hig hly variable due to the tendency of shrimp to congregate and attach to tank walls and bottoms. A direct relationship was observed between po stlarval density and the precision of population estimates in harvest buckets. Water temperature and postlarval age did not affect precision at the densities and ages studied. These findings have important impl ications for commercial transactions. Industry standards utilizing coe fficient of variation are recommended for larvae and postlarvae popula tion estimates.