Development of rotifer strains with useful traits for rearing fish larvae

The euryhaline rotifer Brachionus plicatilis is a species complex, which is commonly used for rearing marine fish larvae. Providing cultures with an appropriate size of rotifers facilitates size dependent selectivity of the feeding larvae and results in larvae with higher survival, growth and stability. It is also important to obtain rotifers with higher growth rate and tolerance against environmental stress and better nutritional quality after enrichment. This paper reviews the importance of feeding rotifers with appropriate size for fish larvae, as well as how much variation of rotifer traits can be expected from natural population of rotifers, as well as from artificial manipulation. These artificial manipulations include (1) manipulation of culture history to establish descendant rotifer clones with different reproductive traits, (2) manipulation of culture environmental conditions and chemical treatments on rotifer traits, such as size and reproduction, (3) cross-mating and a molecular approach for obtaining rotifer strains with useful traits in clones of their descendants. Recent progress on the production of rotifer strains with ideal characteristics in terms of size, population growth, tolerance against external conditions and resting egg formation is discussed.