Use of copepods as live feed for larviculture of damselfishes

Abstract

It is well established that small-sized live feed with sufficient DHA, EPA and ARA as starter feed is the key factor for the success in larviculture of marine fishes with altricial larvae having limited yolk, which are in an undeveloped state at hatching. Copepods form a major component of the natural diet of many fish larvae and the wide range of body sizes of copepods both within and between species is extremely useful for employing the early stage nauplii and copepodites as starter feed for very small larvae with small mouth opening. Improved survival, growth and normal pigmentation have been documented in the larviculture of several marine finfishes reared with the early stage nauplii and copepodites. This is generally attributed to the levels of DHA, EPA and or arachidomic acid (ARA) in the diet and particularly to the DHA: EPA ratio in the diet. Two species of copepods viz. Euterpina acutifrons, a harpacticoid copepod and Pseudodiaptomus serricaudatus, a calanoid copepod were selected and cultured. They were employed as starter feed for the larviculture of three species of damsel fishes viz. the three spot damselfish, Dascyllus trimaculatus, the humbug damselfish, Dascyllus aruanus and the blue damselfish, Pomacentrus caeruleus. It was found that co-culturing of copepods in greenwater in the larviculture tank is the most effective method for initiating the exogenous feeding of the species studied. Initially greenwater was developed in the larval rearing tanks by adding sufficient quantity of the culture of microalgae Nannochloropsis sp. so as to get a cell count ranging from 1 x 105 cells/ml to 6 x 105 cells/ml. Adults of copepods E. acutifrons and P. serricaudatus were introduced into the greenwater. When the copepods started their growth phase, newly hatched larvae were introduced into the tanks. The number of egg bearing copepods and nauplii per 50 ml in the larviculture tanks upto 20-25 days of post hatch is presented. The larval survival in relation to abundance of nauplii and egg bearing copepods is also given. The utility of copepods in the larviculture of damselfishes is discussed in the light of the results of the study.