PARENT SESSION
Oral Session #61: Aquatic Ecology: Fish - Communities and interactions. Presiding: J. Chick.
Thursday, August 9, 2001. 8:00 AM to 11:45 AM. Hall of Ideas F.
Post-settlement use of lagoon habitats as off-reef nurseries for coral reef fishes.
Adams, Aaron1, Ebersole, John1, 1
ABSTRACT- We visually censussed fishes along transects on back-reefs and adjacent lagoons of bank-barrier reefs at six sites on St. Croix, USVI, to determine the extent to which coral reef fishes use lagoon habitats as nurseries. Fishes were recorded by size class {small (< 3cm), medium (3 - 5cm) and large (> 5cm)} on back-reef, and on 5 lagoon habitats: patch reef, rubble, seagrass, algal plain, and sand. We examined densities of four focal 'species' {Acanthurus spp (A. chirurgus and A. bahianus), Haemulon spp (all species of the Haemulon genus), Sparisoma aurofrenatum, and Scarus iserti} and densities of all species combined, and discerned two patterns of habitat use: one group, exemplified by Acanthurus spp, uses lagoon patch reef and rubble as nurseries in preference to back-reef and other lagoon habitats; in contrast, Sp. aurofrenatum and Sc. iserti preferentially use back-reef as nursery, juvenile, and adult habitat. Temporal variation was greatest in the small size class and least in the large size class. Concordance analyses suggest oceanographic influences are most evident in years with high settlement, but only for newly settled fishes of some species, and post-settlement processes modify settlement patterns. For species that use lagoons as nurseries, lagoon habitats must provide advantages that offset the additional energy expense and predation experienced by both incoming larvae, as they cross over the reef into the lagoon, and juveniles, as they return to the reef during the juvenile-to-adult transition.
KEY WORDS: coral reef fish, nursery habitats, ontogenetic habitat shift, post-settlement