Assessing the status of rotifer mass culture

Rotifers are widely used as live larval feed in aquaculture. The stability of rotifer mass cultures, however, remains a critical unresolved problem. It would be useful to develop indicators that can assess the status of rotifer mass cultures and serve as an early warning of trouble. Two indicators have been developed: swimming activity and egg ratio (eggs per female). A swimming activity test is described based on the measurement of rotifer swimming over a grid. Egg ratio is also a sensitive indicator of physiological stress, but there is a 18-24 h time lag between exposure to stress and a change in egg ratio.