Age, growth, and factors controlling post-settlement habitat use of juvenile French grunts (Haemulon flavolineatum) near Tobacco Caye, Belize, Central America
Post-recruitment diurnal habitat use was examined in juvenile French grunts (Haemulon flavolineatum) in the waters around Tobacco Caye, Belize. Two sites were studied: an area near Tobacco Caye and a patch reef 5 km north along the reef crest. ^ Trap collections along two 500-m transects set perpendicular to the reef crest at each site found four habitats which contained fish of different sizes: small juveniles used seagrass beds 50–150 m into the lagoon behind Tobacco Caye, medium and large juveniles used habitats within 10 m of the island and patch reefs to the north of the Caye, and developing adults moved to the fore-reef slope. Daily growth increment formation was shown to occur in sagittal otoliths through a tetracycline mark/recapture study and a growth curve was created by aging fish. French grunts showed a constant growth rate while residing in grassbed habitats, accelerated growth in the island shore and patch reef habitats, and decelerated growth on the fore-reef. Back-reef habitats were vacated within the first year of life. Fish showed high fidelity to their home shoal over short periods, only four of 48 (8.3%) fish in a tag/observation study were observed to move from their home shoal. Three of these movements were interpreted as ontogenetic habitat shifts. ^ Visual surveys along the same four transects indicated that predation, both directly and indirectly by driving diurnal habitat choice, probably had the greatest effect on the distribution of French grunts, although intra-family competition was also important. Lagoon seagrass beds provide a refuge for small juveniles, and probably an excellent background for camouflage. Island shore and patch reef habitats provide suitable refuge for medium to large juveniles, and potential effects of competition and predation are relatively reduced in the island habitat, which supports a higher biomass of fish. The largest juveniles and adult French grunts migrate to fore-reef habitats which have a low biomass due to high mortality in younger fish. A quantitative model accounting for recruitment to grassbeds, mortality, and shifts in habitat accurately predicted the observed age-distributions of French grunts in each habitat at the Tobacco Caye site. ^
Biology, Ecology|Biology, Oceanography
Richard Gust Hein,
"Age, growth, and factors controlling post-settlement habitat use of juvenile French grunts (Haemulon flavolineatum) near Tobacco Caye, Belize, Central America"
Dissertations and Master's Theses (Campus Access).