Changes in Maturation of Chesapeake Bay Striped Bass and the Impacts of Disease on Reproductive Output

The Striped Bass, Morone saxatilis, spawning community in the Chesapeake Bay contributes to over half the coastal population, and is economically and ecologically important. A thorough reproductive study on the Chesapeake Bay Striped Bass has not been conducted since the late 1980s. Since that time, population size has changed dramatically, necessitating an update of reproductive metrics. Additionally, mycobacteriosis is currently infecting over 50% of Chesapeake Bay Striped Bass, and there has been little research on population level effects of the disease. The objectives of this study were to update current knowledge on reproductive metrics of Striped Bass in the bay and examine disease-associated effects of mycobacteriosis. Reproductive and disease data were obtained from female Striped Bass collected from 2003-2007 and 2012-2013 in major tributaries of the Chesapeake Bay and the bay mainstem. An egg-per-recruit model was developed to examine the effects of mycobacteriosis on lifetime reproductive output. Maturation rates were markedly higher than in previous studies, including those used in the current stock assessment, and disease-positive fish were shown to mature significantly earlier than disease-negative fish. Egg-per-recruit model results showed that disease-associated natural mortality effects a 74.4% loss in reproductive output.