Population dynamics and spawning of the flatfish Solea bleekeri and Pseudorhombus arsius in the intertidal area of Inhaca Island, Mocambique

The population dynamics of flatfish Solea bleekeri and Pseudorhombus arsius within the intertidal area of Inhaca Island, Moçambique, was investigated using bottom trawl data collected during summer (December 1996 – March 1997) and winter (June 1997 – August 1997). The endemic S. bleekeri is a small, relatively slowgrowing species with low rates of natural mortality. Densities of juveniles were significantly greater in winter (24.7 fish 1 000 m-2) than in summer (10.8 fish 1 000 m-2), probably because of intensive spawning during summer. Greater catches of S. bleekeri were taken by night than by day. Densities of P. arsius did not differ significantly between day and night or among seasons. Mean density of P. arsius was 53 fish 1 000 m-2 for the survey. Both species preferred the same substrata, significantly greater densities being found on the mudflats and in the tidal channels. Both seem to complete two life cycles within a year.