A method for hatchery culture of tropical calanoid copepods, Acartia spp.
Calanoid copepods of the genus Acartia have proven to be important in the diet of first feeding larvae of golden snapper, Lutjanus johnii, and mangrove jack, Lutjanus argentimaculatus. A simple method for the mass culture of Acartia spp. in the hatchery is described, which reduces the reliance on wild copepod populations and improves the coordination of larval rearing operations. Cultures of copepods were maintained in 100- and 1000-litre tanks and fed daily on a mixed ration of algae, Rhodomonas sp., Tetraselmis sp. and Isochrysis sp., at a total algal cell density of 20 000 cells/ml. The cultures were lightly aerated and the salinity and temperature were maintained between 30-34 ppt and 28-32°C, respectively. The cultures were screened every 8 days to harvest adults and late-stage copepodids and to reduce contamination by rotifers and other undesirable zooplankton. The harvested copepods were used to restart the cultures. Using this method, more than 1000 adult copepods and late-stage copepodids per litre were produced from the 8-day culture cycle. This method has maintained productive cultures for more than 6 months and has been used to produce several batches of L. johnii fingerlings with survival rates of up to 40% at 21 days post-hatch. Adult copepods harvested from the cultures were stocked directly into larval rearing tanks. The copepods continued to breed in the larval rearing tanks and the resulting blooms of nauplii (up to 1.0/ml) were fed on directly by the larvae, eliminating the need to handle the easily damaged copepod nauplii.