Ruano, M. Recruitment of Fish Species in the Arade River Estuary

The fish assemblage of River Arade estuary was characterized by two separated environments, the margins and the tidal channels of the marsh, both sampled during six months (April/September) of 2004 in order to infer its relationship to environmental parameters and its possible nursery function for marine species. In this study were used two sampling methods, beach seine used in margins area and Riley pushnet used in tidal channels. The fish community shows a medium diversity and specific richness, being identified about 41 species and 4 more in preliminary samplings representing globally 23 fish families. The Shannon-Wiener index (H’) and richness (J’) for the margin area were about 1,87 and 0,43 relatively to 37 species, and for the tidal marsh area this values were lower and about 0,32 and 0,12 relatively to 18 species. Two species can be distinguish in the study, the first Pomatoschistus microps dominated in number the marsh channels, it’s a resident specie with a high relative importance, the second Dicentrarchus labrax have dominated the capture in weight and it’s also a resident specie of the estuary with a high importance due his commercial value. Multivariate classification analysis of samples revealed a seasonal standard in the fish assemblage of both habitats. Numerous species used the marsh during the Spring as nursery place, where they can find protection, food diversity and physic conditions that allows that species such as D. vulgaris, S. aurata, S. canthaus, S. senegalensis or A. anguilla growths normally. In margin areas were identified offspring periods for different species that establish here in large groups during initial developing stages (larvae or juvenile), finding here protection against high predation and great variety of sediment and microhabitats, mainly with vegetal cover presence. Species like S. pilchardus, E. encrasicolus, D. vulgaris, S. cantharus, C. labrosus, L. aurata, A. Anguilla or Atherina spp., are a great example of margin resident or temporary resident fish community that use both, the estuary and the marsh channels, as nursery during initial time of life cycle, confirming the high importance of this areas function.