Structure and Seasonal Dynamics of Larval Fish in the Caeté River Estuary in North Brazil

The larval fish assemblage was examined along a salinity gradient of the Caeté River Estuary situated in northern Brazil. A total of 35 555 larvae, representing 28 families and 63 taxa were collected in samples taken monthly between July 1996 and September 1997, with a mean concentration of 9 individuals per 100 m3. Sciaenidae was the most abundant family comprising 46•5% (11 species) of all teleosts sampled in the Caeté River Estuary, followed by Engraulidae (41•9%, seven species). The most abundant larval taxa were the engraulid Anchovia clupeoides and the sciaenid Stellifer microps accounting together for 70•4% of the total catch. The most abundant developmental stages of A. clupeoides was preflexion larva, confirming that this species is resident. Apart from estuarine species, the upper estuary additionally has taxa associated with freshwater conditions, whereas species with marine affinities were captured in the lower estuary. The densities of most species were influenced to a greater degree by site than by season, showing maximum densities in the upper estuary. Larval density peaked in the upper estuary during the dry season and was lowest when freshwater discharge was at its maximum, which was attributed to an increased seaward drift of larvae. Species number was greatest in the upper estuary between the rainy and dry season.