Evaluation of substitute diets for live algae in the captive maintenance of adult and subadult unionidae

Ten nonlive algal diets were evaluated as potential broodstock diets for adult and subadult unionids. These diets varied significantly in their ability to support growth, reproduction and survival. Growth, increase in glycogen stores, and limited glochidial formation were seen in most unionid species on two of the diets. However, long-term survival (>3 y) remained problematic, and the cause of mortality in these animals could not be determined. While two of the diets tested are potentially useful for supplemental feeding of adult unionids to increase glycogen levels during quarantine, or during short-term captive maintenance in the laboratory, none can be recommended without reservation for long-term maintenance because of the lack of survival after three years during this study.