Pilot-scale production of the rotifer Brachionus sp. under different culture systems

Small Brachionus sp. (130-230 µm) in 2011-2012 and tiny Brachionus sp. (110-140 µm) in 2013-2014 were reared in batch culture (3 or 4 day cycles) and semi-continuous systems. For feeding rotifers, nonviable microalgae (Nannochloropsis sp.) were used and were continuously dosed with peristaltic pumps. The cultures provided air, oxygen, and sodium hydroxymethanesulfonate. An average total daily production of 552, 602 and 459 million rotifers d-1 with mean final densities of 1,099 rotifers mL-1, 1,052 rotifers mL-1 and 1,015 rotifers mL-1 were harvested in three day (3-d) and four day (4-d) batch culture systems and semi-continuous culture systems, respectively. The average values of rotifers produced were adequate to supply the rotifers required in the parallel pilot rearing larval cycles, and 169 x 103 /yr (2012) to 564 x 103 (2013) juveniles/yr were produced with a mean annual demand of 83.9 x 106 rotifers/1,000 juveniles produced. The total operational cost per million rotifers/day was lower for the semi-continuous culture system ($0.23), followed by the 4-d batch system ($0.55) and 3-d batch system ($0.59). These production costs were lower than those of other reports with artificial feeds and recirculation systems. The main components of the total operational cost was food (71-77%) and labor (7-11%). The best production stability and reliability were in the semicontinuous system, which best met the required daily quantities for the larval rearing trials. For possible improvements and increased production, the results are discussed in terms of financial efficiency.