Importance of shallow-water biotopes of a Caribbean bay for juvenile coralreef fishes: patterns in biotope association, community structure and spatial distribution

Fish community structure of a non-estuarine inland bay on the Caribbean isl and of Curacao was determined in the mangroves, seagrass beds, algal beds, channel, fossil reef boulders, notches in fossil reef rock, and on the adja cent coral reef, using visual censuses in belt transects. Fish communities varied among biotopes, but some overlap was present. Fish density and speci es richness were highest at the boulders and on the coral reef, and extreme ly low on the algal beds, whereas the total number of individuals calculate d for the entire bay was highest on the seagrass beds. Differences in fish densities between biotopes were related to differences in structural comple xity and amount of shelter. Fishes in the bay largely consisted of 17 (main ly commercially important) reef fish species, which used the bay biotopes o nly as a nursery during the juvenile part of their life cycle. Small juveni les of these species were most often found in the mangroves, whereas at int ermediate sizes some were found in the channel. Large individuals and adult s were found on the reef, and densities of several of these species were hi gher on the reef near the bay than on reefs located farther down-current. F ishes which spent their entire life cycles in either the bay or on the cora l reef were also found, and the latter group showed a strong decrease in ab undance with increasing distance into the bay. The density distribution of individual fish species was not homogeneous within the bay. In the mangrove s and seagrass beds, spatial distribution of fishes was correlated with dis tance to the mouth of the bay, water transparency, amount of shelter, and t he structural complexity of the biotope. juveniles of 3 reef species showed an increase in size on the seagrass beds with distance from the mouth into the bay, whereas 1 bay species showed a decrease in size with this distanc e.