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Notes
- Abstract:
- Conservation efforts for Nassau grouper have primarily focused on offshore aggregation sites but juvenile development is also crucial to maintaining healthy population numbers. Juvenile Nassau grouper live within seagrass beds for 1-2 years where they forage within seagrass blades and utilize complex microhabitats within seagrass beds for refuge. An invasive seagrass, Halophila stipulacea, has spread throughout the Caribbean and has been found as monotypic stands and mixed with native seagrasses. H stipulacea has considerable morphological differences to the Caribbean native seagrasses, which can influence the survivorship of juvenile fish. The purpose of this study is to determine if the structural differences between native and invasive seagrass blades influence juvenile development.
Canopy height, blade density, and percent cover of the different seagrasses were compared between sites where juveniles were found and random sites where they were absent. Juveniles were more abundant in seagrass habitats with tall canopy heights and low densities. H stipulacea beds were characteristically shorter and denser than the native seagrasses, which suggested that persistence would be lower in areas with high %H stipulacea cover. The native blades in mixed stands influenced grouper persistence by increasing canopy height and intercanopy space which complicated the relationship between %H stipulacea cover and persistence.
The condition of each juvenile was assessed and compared to the physical characteristics of the seagrass surrounding them. Seagrasses with taller canopy heights and lower blade densities harbored juveniles with higher condition values. The only healthy juveniles found within H stipulacea were under 9cm in total length. Mixed and native seagrasses harbored healthy individuals up to 30cm in total length, suggesting that the presence of native blades is necessary for growth and survival.
The morphological differences of H stipulacea may serve as a sufficient habitat for the smallest juveniles, but this study suggests taller and less dense blade structure of native seagrasses is necessary to increase condition of larger juveniles. Although the blade morphology of H stipulacea is not optimal for juvenile growth, mixed stands harbored small and large juveniles with high condition values. Results from this study highlight the importance of preserving tall native seagrasses to increase the persistence and condition of juvenile Nassau grouper. This information is not only useful for juvenile Nassau grouper, it is applicable to other coral reef fish that rely on seagrass beds for nursery habitats throughout the Caribbean.
Record Information
- Source Institution:
- University of the Virgin Islands
- Holding Location:
- University of the Virgin Islands
- Rights Management:
- Copyright Damon B. Green. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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