USE OF SWIMMING SPEED AND EGG RATIO AS PREDICTORS OF THE STATUS OF ROTIFER CULTURES IN AQUACULTURE

This study evaluated the use of egg ratio (eggs rotifer(-1)) and swimm ing speed (mm min(-1)) as prediction criteria for production and cultu re quality in mass cultures of the rotifer Brachionus plicatilis. Egg ratio was determined to be a suitable predictor of rotifer growth and production in the cultures. Low egg ratios (i.e., 0-0.17 eggs rotifer( -1)) indicate reduced rotifer population over time (i.e., negative net population growth rates). However, at this time egg ratio dynamics ar e not suitably understood to predict in advance a sudden population co llapse. Swimming speed of reproductive, egg-carrying females in the ex ponential growth phase was 40-45 mm min(-1) During exponential growth swimming speed was independent of the food used. Lower swimming speeds were obtained in late stationary phase (10-25 mm min(-1)) when yeast was used as a food source. Both environmental factors (e.g., accumulat ing metabolites) and changes in nutritional state of the rotifers may have affected the swimming speed, but environmental factors appear to be the most important. We believe that swimming speed has the potentia l of becoming an accurate predictor of culture quality in mass culture s of rotifers.