A method for hatchery culture of tropical calanoid copepods, Acartia spp.

Calanoid copepods of the genus Acartia have proven to be important in the d iet of first feeding larvae of golden snapper, Lutjanus johnii, and mangrov e jack, Lutjanus argentimaculatus, but it is difficult to reliably harvest these copepods from the wild. To overcome this problem, we present a simple method for the mass culture of Acartia spp. in the hatchery. This reduces the reliance on wild copepod populations and improves the coordination of l arval rearing operations. Cultures of copepods were maintained in 100 and 1000 l tanks and fed daily with a mixed ration of algae, Rhodomonas sp., Tetraselmis sp. and Isochrysi s 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 degrees C, respectively. The cultures were screened every 8 days to harvest adults and late-stage copepodids and to reduce contamina tion 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 c ulture cycle. This method has maintained productive cultures for more than 6 months and has been used to produce several batches of L. johnii fingerli ngs 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 resul ting blooms of nauplii (up to 1.0/ml) were fed on directly by the larvae, e liminating the need to handle the easily damaged copepod nauplii. (C) 1999 Elsevier Science B.V. All rights reserved.