Seagrass ecosystems provide essential nursery habitat to numerous coral reef fishes. Native Caribbean seagrasses Syringodium filiforme and Thalassia testudinum provide several juvenile fish species with foraging habitat and protection during this vulnerable stage of life. In 2002, an invasive seagrass Halophila stipulacea was discovered off the coast of Grenada and has since rapidly spread throughout the Caribbean. Halophila stipulacea has been shown to displace native seagrass species and may pose additional threats to juvenile reef fish populations that depend on native seagrass habitats as nurseries. The purpose of this study was to determine the effects of H. stipulacea on the early life history of yellowtail snapper (Ocyurus chrysurus). Settlement, mortality, and condition of juvenile yellowtail snapper were compared among native and invasive seagrass habitats around southern St. Thomas, United States Virgin Islands. From May 2020 to June 2021, monthly surveys within fixed plots during new moon periods provided information on settlement rates and survivorship among seagrass types. Length and weight of 260 juvenile yellowtail snapper were measured to derive condition factor among seagrass species. Significantly higher settlement and similar trends in mortality were seen in H. stipulacea when compared to native seagrasses. No significant difference was observed in the condition factor of juvenile yellowtail snapper among seagrass species, although trends demonstrated a higher condition in individuals from native seagrass species. This study is the first of its kind to identify the direct effects of H. stipulacea during the early life history stages of a commercially important fish species in the Caribbean.
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