Map of Fishery Habitats Within the Virgin Islands Biosphere Reserve

Boulon, Ralf

REPORT N0.8 Subtask 2.1 MAP OF FISHERY HABITATS WITHIN THE VIRGIN ISLANDS BIOSPHERE RESERVE: Nineteen naturally occurring and one man-made benthic community habitat types are described in terms of the commercially important fish species assemblages found occurring there. Marine habitat types were mapped for all of St. John from NOS (National Oceanographic Survey) aerial photographs and groundtruthed by divers from January to May 1984 to determine accuracy of mapping and to describe each habitat in detail. Fish species assemblages are determined using a random point. visual census technique which appears to be quite accurate. is easy. fast. and repeatable by anyone with minimal instruction. Results indicate that each benthic habitat type can be distinctly described in terms of its unique fish species assemblage and life history function. The life history function is viewed as a continuum primarily related to distance from shore and depth with habitats like mangrove shoreline and back reefs being juvenile refuges and deeper offshore habitats like lower fore-reefs and.bank patch reefs being mature fish habitats where most reproductive activities take place. Habitat types similar to each other in species assemblage generally share similar structural complexity or structural components. Habitats with greater structural complexity tend to contain a greater number of species. In addition to demersal fin fish. lobster, conch and whelk are other heavily exploited fishery resources. Lobster populations appear to be quite low and appear to be highest in the deeper. more structurally complex habitats. Conch are less common in shallower habitats, possibly due to overfishing. but are frequently found in the deeper grassbeds seaward of coastal reef systems. With a limited. narrow habitat. which is very accessible to fishermen. whelk populations are extremely low with few large. mature individuals found. Both migratory pelagic fish species and baitfish require substantial work before enough is known to even attempt to draft management guidelines.