MEPS 237:247-256 (2002)  -  doi:10.3354/meps237247

ABSTRACT: Visual censuses of recently settled yellowtail snapper Ocyurus chrysurus were made within a grid measuring 50 x 25 m established in a <1 m deep seagrass (Thalassia testudinum) bed in the British Virgin Islands, eastern Caribbean, between September 1999 and July 2000. A peak of 92 newly settled O. chrysurus was observed around the new moon in September 1999, followed by a decline of more than 75% over 3 wk. Light trapping near adjacent fringing reefs documented a concurrent pulse of late pelagic stage O. chrysurus. Observations in April-May and June-July 2000 recorded much smaller supply events and lower settlement densities. The effects of post-settlement movement, as opposed to early mortality, were assessed and concluded to be negligible. Firstly, fish <8 cm total length were consistently observed in the seagrass but were never recorded in censuses of adjacent rocky habitat, where older juveniles occurred. Thus, settlement-stage fish were assumed to reside in seagrass for several weeks. Second, average home ranges for fish of 2 to 2.5 cm and 3 to 3.5 cm total length were estimated to be 2.3 m² and 6.3 m², respectively, indicating that movement of newly settled O. chrysurus was negligible compared to the size of the census area (1250 m²). Third, late pelagic-stage O. chrysurus caught with light traps in adjacent waters were tagged with fluorescent elastomer and released at the center of the seagrass grid the evening after their capture. Ninety-six individuals were released over 3 evenings in September 1999. Concurrent aquarium studies showed tagging mortality was 13%. Over the following 8 d, 32 re-sightings were made. Only 1 fish was seen more than 2 to 3 m distant from where it was sighted on the first census after releases were completed, providing convincing evidence of site fidelity after settlement. Using a simple model, we conservatively estimated the coefficient of daily mortality, M, at settlement to be about 0.28 (equivalent to 76% survival d^-1) and to reduce by 0.042 thereafter.

KEY WORDS: Caribbean · Coral reefs · Fisheries · Elastomer · Recruitment