The reproductive biology of Chesapeake Bay striped bass with consideration of the effects of mycobacteriosis

The Chesapeake Bay spawning population of striped bass, Morone saxatilis (Walbaum, 1792), is the principal contributor of juveniles to the coastal Atlantic population, but a thorough reproductive study has not been conducted since the early 1990s, prompting questions about temporal changes and stock density-related impacts on reproduction. Additionally, mycobacteriosis, a chronic lethal bacterial disease, is currently affecting >50% of Chesapeake Bay striped bass, and disease-associated impacts on reproductive biology are unknown. To provide a contemporary description of Chesapeake Bay striped bass reproduction and examine possible effects of mycobacteriosis, we obtained reproductive data and disease prevalence information from females collected from 2002 to 2016. Fecundity-at-length generally was consistent with published literature suggesting that fecundity has not changed over time. Prevalence of mycobacteriosis had no significant effect on fecundity, but most disease-positive fish were only mildly infected. Age at 50% maturity (2.84 yrs) was lower than all previous reports (range 3-7 yrs). It is possible that the discrepancy is due to a lack of standard methodology for staging striped bass oocytes or to spatiotemporal differences in maturation rates. Disease-positive fish generally matured earlier and at smaller sizes than disease-negative fish (age at 50% maturity = 2.65 and 2.94 yrs, respectively; length at 50% maturity = 322.21 and 342.62 mm, respectively). The results of this study reveal that the maturity ogive for striped bass needs to be re-evaluated throughout the species range, and that mycobacteriosis may have a negative impact on reproductive success. Future research should assess how disease severity effects reproductive biology.