Evaluation of the production of Brachionus plicatilis rotifers using different initial stocks and different concentrations of Nannochloropsis oceanica microalgae
The production of the Brachionus plicatilis rotifer is essential for the development of marine fish larviculture, since it is commonly used as the first food for larvae. The use of the microalgae Nannochloropsis oceanica as food allows the production of rotifers on a large scale. To create a production protocol, the initial density to be inoculated and the amount of food used must be calculated according to the need for rotifer production. The experiment carried out was designed from the factorial statistical model of Central Rotational Composite Design. The experiment was carried out for 72 hours and used 11 experimental units with a useful volume of 2 L. The rotifers were stored in different densities (59, 100, 200, 300 and 341 rot mL-1) and fed with different concentrations of N.oceanica (59, 100, 200, 300 and 341 × 109 cel 106 rot-1 day-1). After the experimental period, response surface graphs were generated for the results of population growth rate, proportion of ovate females, non-ionized ammonia and cost. In addition, using prediction profilers, three production scenarios were created: Optimized Scenario, with maximized level of desirability, using 270 × 109 cell 106 rot-1 day-1 and a storage density of 69 rot mL-1; Maintenance scenario, with microalgae quantity and reduced cost, using 140 × 109 cell 106 rot -1 day-1 and a storage density of 180 rot mL-1; and Maximized Production Scenario, with maximized population growth rate (0.53), using 300 × 109 cell 106 rot-1 day-1 and a stocking density of 100 rot mL-1. This study confirmed the efficiency of N.ocean as an exclusive food source for the production of rotifers. In addition, the stocking density of rotifers is significant for its population growth rate, however, it is necessary to better understand the reasons for this influence.