THE ABUNDANCE AND DIVERSITY OF LARVAL AND JUVENILE FISH IN A TROPICALESTUARY

The larval and juvenile fish of the Cayenne river estuary (French Guia na, South America) were sampled at two stations from June 1989 until O ctober 1990. A total of 52,989 individuals from 59 species, some still incompletely identified, were collected. Three families, Engraulidae, Gobiidae and Sciaenidae, accounted for over 97% of the total number o f juveniles. The analysis of data over this period showed low diversit y, and a difference in diversity between the two sampling locations (H ' = 1.24 and 1.68). The results conform to some theoretical models of abundance that suggest a relative equilibrium of juvenile assemblages. In contrast, the seasonal variations in diversity and abundance and t he results of a correspondence analysis showed significant differences in species distribution and in their relative abundance at the two sa mpling locations at certain periods, mainly in the rainy season. Our s tudy indicates that, in spite of an apparent stability the year to yea r variation in salinity and freshwater inputs could affect juvenile re cruitment of some species and induces modifications in the composition of larval and juvenile estuarine fish assemblages.