Quantifying trends in and potential drivers of mycobacteriosis in Atlantic Striped Bass in Maryland waters of the Chesapeake Bay

ABSTRACT Objective The outbreak of mycobacteriosis among Atlantic Striped Bass Morone saxatilis in the main-stem and Virginia portions of the Chesapeake Bay has been shown to impact their survival, growth, and fecundity. In this study, we analyzed long-term fish health monitoring data from the Maryland portion of the Chesapeake Bay to identify disease trends and potential drivers. Methods This study explored trends in mycobacteriosis prevalence and severity and the influence of environmental and nutritional stress on disease dynamics for Striped Bass in Maryland waters of the Chesapeake Bay using generalized linear models of long-term fish health data and estimates of hypoxia and temperature. Results The proportion of Striped Bass ages 0–1 sampled in Maryland waters of the Chesapeake Bay that tested positive for mycobacteriosis (apparent prevalence) increased during 1998–2017, with a peak of 67% in 2016, and disease severity increased with age for both sexes. Disease prevalence in age-0–1 premigratory Striped Bass was related to high water temperature duration, hypoxic volume, and fish condition. Prevalence of severe external disease symptoms was related to high water temperature duration, hypoxic volume, fish condition, age, and sex. Relative mortality of severely diseased fish implied by our severity model approximately doubled across the range of hypoxic volume and high water temperature duration examined. Conclusions Mycobacteriosis is widespread in Maryland waters of the Chesapeake Bay and is negatively affecting Striped Bass survival, particularly for severely diseased fish. Limitations of suitable habitat related to poor water quality and climate change are likely influencing disease prevalence and severity.