Use of ultrasonic imaging to assess the reproductive status of striped bass in the Savannah River Estuary

Ted A. Will, Thomas Reinert
Georgia Cooperative Fish and Wildlife Research Unit, D.B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602-2152; Phone: 706-542-5260, Fax: 706-542-8356, email: twill@smokey.forestry.uga.edu, treinert@uga.edu

Cecil A. Jennings
United States Geologic Survey - Biological Resources Division, Georgia Cooperative Fish and Wildlife Research Unit, D.B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602-2152 Phone: 706-542-5260, Fax: 706-542-8356, jennings@smokey.forestry.uga.edu

The abundance of striped bass in the Savannah River Estuary (SRE) declined dramatically during the late 1980's. A state-sponsored stocking program has increased the number of adults in the SRE. Nonetheless, the abundance of eggs and larvae remain well below historic levels. Whether these low densities are related to the maturational status of the population or to a lack of suitable spawning conditions is unknown. The primary cause of the population decline has been remedied, and environmental conditions seem suitable for striped bass spawning; however, the current maturational status and fecundity of this population are unknown. During Spring 1999, we used ultrasonic imaging techniques to examine the ovaries of 31 striped bass from the SRE. We also took one 1-mm sample of ovarian tissue from each female and used the samples to enumerate eggs and estimate their maturational stage. We used these data to develop a model (V= -0.257 + 1.04 [log of mean ovary diameter] + 1.56 [log ovary total length]; R²=0.96) that predicts ovary volume and will be used to predict total fecundity and maturational status of striped bass in the SRE. Assessing the maturational status of this population will improve environmental mitigation efforts and fisheries management decisions.