Veiga, P. A study on the ichthyofauna from the Castro Marim and Vila Real de Santo António salt marsh.

Fish communities of the Castro Marim salt marsh were studied based on monthly sampling surveys at five sites, between September 2000 and August 2001. A beach seine was the sampling gear used to capture the fishes. A total of 7955 fish specimens (37995,7 g), comprising 34 species and 17 families were sampled. The occurrence of most species was occasional, with Pomatoschistus microps and Atherina spp. (10,3%) being the most abundant species, together accounting for 62,2% of the total fish captured. The biomass was dominated by the marine species Liza ramada (15,9%), Mullus surmuletus (13,5%) and Liza aurata (13,4%). The abiotic parameters temperature and salinity had a seasonal pattern, with minimums in winter months and maximums in summer months. This pattern seems to be reflected in the fish assemblages, which present two distinct compositions in the two periods. A few species, with dominance by the residents and the presence of freshwater species, characterised the Winter fish assemblage; the Summer communities were characterised by the presence of many marine visitors, that use the salt marsh in their first months/years of life. Temperature was the parameter that proved to be most important in explaining the community structure. Temporal variations in total abundance and biomass reflected fluctuations in the dominant species. Resident species presented the highest abundance values, while marine species that use the salt marsh as a nursery ground and marine adventitious had the major contribution for community species richness. Castro Marim salt marsh constitutes an important ecosystem for fishes, since it provides habitat for many species, mostly juveniles, which find here suitable conditions for their development.