Rotifers (Brachionus spp.) have been used as a live food for feeding larval marine fishes for over 30 years. Today, more than 60 marine fish species and 18 crustacean species require adequate and reliable production of high-quality, nutritious rotifers (Qi et al., 2009). The rotifers are considered to be euryhaline (Bosque et al., 2001) and can tolerate a wide range of salinity (Øie and Olson, 1993). However, the optimum salinity range for their culture is much narrower. Salinity affects the life history traits (Oltra and Todoli, 1997) and demographic characteristics (Bosque et al., 2001) of rotifer. Furthermore, some of the reproductive features of rotifers in a culture such as induction of mixis and the production of cysts have been linked to the salinity of their culture medium (Kostopoulou et al., 2007). In this study the effects of different culture salinities on the population changes and reproductive characteristics of two native Brachionus rotifers from Iran are investigated.
