**1. Introduction**

342 Aquaculture

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The availability of highly nutritive and inexpensive live food is a subject of major concern in aquaculture industry particularly for the fry production activity. For so long, the aquaculture industry has relied primarily on brine shrimp and rotifers to provide the necessary nutrition for rearing the early life stages of fish and crustaceans. Brine shrimp and rotifers are almost not suitable as first feed for fish larvae due to inappropriate size (too large or too little) (van der Meeren, 1991; Pepin & Penney, 1997), their swimming behavior makes them less susceptible to predation (Buskey et al., 1993; von Herbing & Gallagher, 2000), and insufficiently nutritious (Støttrup & Norsker, 1997). Because of these problems, brine shrimp and rotifers become uneconomical as live food. This initiate the great interest in the identification of alternative live feeds to meet the demands of the aquaculture industry.

Copepods are among the most abundant and important components of aquatic invertebrates in many marine and freshwater ecosystem. They become the major biomass in zooplankton community in the water column, and at many occassions they form significant entity of benthic community structure on bottom sediment.They are a major food source for organisms in higher tropic level such as juvenile fishes and shrimps (Vincx, 1996; Penchenik, 2005) thus they become link between primary producer and other consumers in the natural food-web.

There have been a number of studies providing evidences of the effectiveness of copepods as a food item, and many investigators reported a good growth and survival of fish larvae and crustaceans fed with copepods as test food organisms (van de Meeren, 1991; Holmefjord et al., 1993; Naess et al., 1995; Støttrup & Nosker, 1997). This is due to the good nutritional profile of copepods which meets the nutritional requirements of marine fish and crustaceans larvae as they are rich in essential fatty acids (Støttrup & Norsker, 1997).

Amongs the copepod group, harpacticiod copepods are known to be mostly benthic (Pechenik, 2005), meaning they live on bottom habitat such as sediment or bottom vegetation. They could live as epi-(dwelling on the bottom surface), endo-(burrowing into bottom surface) or mesobenthos (living between grain particles or in pore water in the bottom sediment). As they lead a benthic living mode, they depend on the diets available on bottom habitat including phytobenthos, microbes and detritus.

Harpacticoid copepods has been found to be a good candidate in aquaculture industry since they have a high reproductive potential, short generation time, high population growth, flexible in diet and tolerate a wide range of environmental factors such as temperature and salinity (Sun & Fleeger, 1995; Støttrup & Norsker, 1997). They provide a broad spectrum of prey sizes suitable for fish larvae (Gee, 1989). There are reports that indicate the availability of enzyme in harpacticoid copepods which enable the organisms to convert any type of their organic food into lipids stored in their body (Nanton & Castel 1998; Drillet et al. 2011).

The prominent problem in using copepods as live feed in aquaculture industry is to get high yield due to several reasons which mainly related to the culture technique. Pure culture is difficult to maintain in ponds or in hatchery on a continuous basis. Although continuous cultivation of marine copepods has been achieved, but it is only for a small number of species. Several species of harpacticoid copepods that have been cultivated either for commercial use or laboratory level are *Tisbe holoturidae, Tisbe beminiensis, Nitokra lacustris* and *Tigriopus japonicus*. As reviewed by Rippingale and Payne (2001), harpacticoid copepods especially *Tisbe* spp (Støttrup & Norsker, 1997) and *Tigriopus* spp (Carli et al., 1995) were the easiest to culture. Nevertheless, the technology to economically culture marine copepods to get highly enough yield is still being developed to date (Marcus & Murray, 2001; Rhodes, 2003; Drillet et al., 2006).

Lacking in information about the basic biology, reproduction and response of copepods in rearing environment could be one of the reason why mass culture technique is yet to be successful for copepod production. Harpacticoid copepods in particular need special attention as they are predominantly benthic in nature. This chapter will discuss on important aspects in rearing harpacticoid copepods as live feeds in aquaculture.
