Robert D. Quinn and James B. Layzer, U.S. Geological Survey/Biological Resources Division, Tennessee Cooperative Fishery Research Unit, Tennessee Technological University, Cookeville, TN 38505

Abstract. In response to the introduction of zebra mussels into the Cumberland and Tennessee river drainages, unionids translocated from these river systems are routinely quarantined for 30 days. To date, little is known about the factors that may affect survival during quarantine. Therefore, we conducted five quarantine experiments between May and December of 1996. Our objective was to determine the highest density for quarantining the freshwater mussel Fusconaia ebena that would still result in high overall survival, and negligible risk of zebra mussels surviving or escaping visual detection. During most experiments, F. ebena were held at densities of 50, 100, 150, 200, 250, and 300 per 760 L. These unionids were fed a dehydrated culture of Spirulina platensis at a rate of 0.05 g/unionid/3d. Apparent trends in mortality during and following the quarantine were inconsistent among seasons. For instance, mortality was density dependent in October and ranged from 26% in the lowest density tank to 68% in the highest density tank; however, mortality in November did not exceed 1% for any density tested. Overall survival of the 30-day quarantine period seemed to follow a pattern of seasonal variation with the highest survival during May and November, and the lowest survival during July. This seasonal variation in survival closely paralleled a previously identified trend in condition of F. ebena at this site.