CONTINOUS SUPPLY OF ROTIFERS AT LOW CONCENTRATIONS FOR LARVAL CULTURE OF RED DRUM Sciaenops ocellatus

Jason Lemus* and Kerry Mesner
 
Fish and Wildlife Research Institute
Florida Fish and Wildlife Conservation Commission
14495 Harllee Road
Palmetto, FL 34212
jason.lemus@myfwc.com
 

Intensive production of live foods is expensive yet is necessary for intensive larval culture of marine fish. Although higher concentrations of live foods, such as rotifers, fed to fish larvae (larvae) provide greater opportunities for larvae to encounter and ingest prey, negative consequences including excess production of rotifers, and liver disease of larvae may result if food consumption is in excess of nutritional needs. A targeted rotifer concentration (rotifer/mL) that leads to efficient rotifer consumption by larvae can be maintained in larval culture tanks by automated pumping of rotifers from cold-storage at concentrations specific to larval age or size. An experiment was conducted to determine the effect of continuous rotifer abundance on ingestion by larval red drum, and their growth, survival, and liver condition. Three levels of rotifer concentrations maintained continuously in larval culture tanks were compared. Rotifer abundance was established at the initation of the 14-hour photoperiod and maintained continuously throughout by automated pumping and direct tank feeding of rotifers. In-tank rotifer estimates were used to guide adjustments to the rotifer concentration in the larval tanks. Rotifer concentration did not affect survival. Ingestion of rotifers increased with larval age and rotifer concentration, but growth was affected only at the lowest rotifer concentration, 0.5 rotifers/mL.  Hepatic lipidosis was evident early in the larval period for rotifer concentrations higher than 0.5 rotifers/mL and persisted into advanced larval stages, indicating a negative association between rotifer ingestion and larval health. The data indicates that larval red drum can be aquacultured effectively by maintaining a relatively low rotifer concentration for intensive aquaculture (0.5 rotifers/mL) in tanks continuously with minimal effects to growth. Although, for production purposes a flexible feeding schedule for intensive larval production may permit a higher rotifer concentration to buffer against rotifer depletion and inter-tank variability, improved fish health and use of resources occur when continuous rotifers supply is closer to the minimum requirements for maximum survival and growth.