Abstract

Invasive Indo-Pacific lionfish Pterois volitans/miles have established high population densities in many western Atlantic marine habitats and regions. However, high densities and low genetic diversity could make their populations susceptible to disease. We examined changes in northern Gulf of Mexico (nGOM) lionfish populations following the emergence of an ulcerative skin disease in summer 2017, when disease prevalence was as high as 40%. Sex-specific relative condition was 8.8% lower for ulcerated female lionfish versus non-ulcerated females. Analysis of lionfish size composition during 2014 – 2018 indicated the abundance of new recruits declined by >80% in spring and summer 2018, then returned to near pre-disease levels by that fall. Remotely operated vehicle surveys indicated mean lionfish density in 2018 declined 75 – 79% for high-density populations (>25 fish per 100 m2) on artificial reefs, 52 – 62% for low-density (<15 fish per 100 m2) artificial reefs, and 75% for populations on natural reefs. Regional commercial lionfish spearfishing landings and catch per unit effort (CPUE) also declined approximately 50% in 2018. Lionfish tournament mean CPUE declined 44% in 2018 and an additional 18% in 2019. Collectively, these results provide evidence for density-dependent epizootic population control, given the gross pathology of the disease, the effect in relative condition for ulcerated females, and that lionfish highest disease prevalence and strongest declines were on high density reefs.

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