A Technique on the Culture and Preservation of Marine Copepod Eggs

Abstract

The search for the ideal copepod for marine fish larvae that can be cultured intensively is ongoing. Copepods are nutritionally suitable for marine fish larvae (Sargent et al. 1997; Stottrup 2000) and constitute a large percentage of the diet in the natural environment (Hunter 1981; Munk and Nielson 1994). Moreover copepods are way too higher in nutritional composition when compared to the traditional live feeds such as Artemia nauplii and rotifers. But it is difficult to culture copepod at sufficient densities to be economically efficient on a commercial scale, because they require high water volumes for cultivation in captivity (Esmaeili et al. 2011). Even though more than 12,000 species of copepods have been identified and classified (Humes 1994), a few species only are being cultured for the purpose of rearing fish larvae. Out of ten orders of copepods, only three orders, viz., Calanoida, Harpacticoida, and Cyclopoida, are being cultured widely around the world. Among these, the calanoid species receives much attention due to their abundance in pelagic waters and ease of culture in controlled environments. Apart from this, many calanoid copepods are capable of releasing free eggs unlike the cyclopoid and harpacticoid copepods which release their nauplii from the egg sacs itself. The production of diapause eggs has been recorded in many calanoid species during abnormal environmental conditions. These diapause eggs can undergo a long period of metabolic arrest until the environment turns to favorable conditions. This fact aids in the storage of diapause eggs for a longer period and could be used for culture when needed.