Intrinsic rate of population increase (r) was evaluated as a measure of population dynamics of four strains of Brachionus plicatils and two strains of B. urceolaris in response to different salinities and foods. Each rotifer strain was cultured at four salinities, 5, 20, 25 and 30 ‰ and fed with two microalgal species, Chlorella vulgaris and Nannochloropsis occulata. Salinity of 5 ‰ was critical for all the examined strains, at which, r was at minimum and was different from the other salinities (P<0.05). For the strains of B. plicatilis, the maximum r was for Chlorella fed group at 10 and 30 ‰ (64±0.01 day−1). While, in B. urceolaris, maximum r was for Nannochloropsis fed rotifers at 20 ‰ (0.69±0.01day−1). Maximum final population density (FD) was obtained for a strain of B. urceolaris fed Nannochloropsis at 20 ‰ (329.3±10.9 ind.mL−1). FD was relatively lower in B. plicatilis strains in all examined salinities. The effect of food on the estimated parameters was under the cumulative effect of salinity. In general, feeding on Nannochloropsis resulted in higher growth performance in the examined rotifers. Besides, the cumulative effects of salinity×algae caused significant difference in r value of most strains
