Abstract

Sampling of mangrove, seagrass (Thalassia, Syringodium and Halodule) and nearshore sandy habitats over 13 months in Jamaica's largest bay, adjoining the country's largest landing site, yielded 98 species, comprising 92 finfish species from 41 families, including three elasmobranchs families, plus eight crustacean species from six families, and two molluscan species. Adult, sub-adult and juvenile fishes were captured with two types of seines nets deployed in shallow waters of not more than 2m depth. A total of 18.16 kg of fishable species were taken comprising 2,389 individuals, confirming the small sizes taken. Most (69%) of the 92 finfish species carne from mangrove-seagrass habitats, and were represented entirely by juveniles.\The five most abundant fish species numerically were Anchoa lyolepis (dusky anchovy), Eucinostomus gula (silver jennny), Sardinella anchovia (Spanish sardine), Diapterus rhombeus (caipita mojarra), and Haemulon sciurus (bluestriped grunt). Crustaceans comprised 7.1 % with Callinectes spp. (blue swimming crab) the most abundant species, with molluscs contributing 2% of all species taken.\Species richness for the total area is high (SR=98), and not unlike that (SR=87) found in the Florida Everglades by Thayer et al. (1987). Similarity in diversity between sample stations and areas were measured using Jaccard's coefficient of similarity, and preliminary results suggest diversity in adjoining bays was sometimes different from each other. Mangrove-seagrass complexes in eastem Portland Bight had higher species diversity than westem, despite nearly identical ecology and physico-chemical characteristics. Portland Bight and the area just west of it was shown to possess important juvenile fishable resources which occupied shallow nearshore zones as well as deeper areas that are fished commercially. Two commercially important marlne shrimp species (Penaeus schmitti and P. notialis, southern white and southern pink shrimps) were caught.\Despite limited sampling, it was apparent that some areas functioned as critical nursery areas for many species and that the entire area as a whole, appeared to function as a giant nursery for many useful species. These fishable resources are inextricably linked with the larger body of resources landed at Old Harbour Bay beach, Jamaica' s largest fish landing site, through movement from the Portland Bight area into deeper, exploited reef areas and through directly supporting the commercially fished reef species by providing fomge species. The economic value of the fishable resources is thought to be so great that loss of these nursery areas through poorly planned development or other means, would affect the livelihoods of several thousand fishers, as well as equal numbers of directly dependent vendors and their respective families in adjoining parishes. This study was limited to very shallow waters, and thus, sampling of waters deeper than 2m would be necessary for a more complete assessment

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