THE INFLUENCE OF FISH FARMING ON POLYCHAETE COMMUNITY STRUCTURE
Salas, F.; Gimenez-Casalduero, F.; Belmonte, A.; Aliaga, V.; Marcos, C. & Perez-Ruzafa, A.
Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, Campus Universitario de Espinardo, 30100, Murcia, Spain.
In recent years, fish farming using suspended cages has been developed in the coastal areas of the world. This activity is often accompanied by serious organic pollution of the water and sediment. Organic pollution tends to cause environmental disturbance to the planktonic, nectonic and benthic communities (Beveridge, 1984; Tsutsumi & Kikuchi, 1983; Tsutsumi et al., 1991). Monitoring of marine benthic community structure is a common approach to environmental impact assesment. The community structure of polychaetes near to the cages was investigated as na indicator of benthic disturbance. During 1996-1997 two sites in different areas of Cabo Tiooso (SE Spain, Mediterranean sea) were sampled. Sampling stations were located at predetermined positions in the proximity of the cages and at undisturbed sites (control stations). Three replicates were taken at each station. Preliminary results show 71 species of polychaetes belonging to 16 families dominated by the Syllidae (26 species), Nereidae (8 species), Phyllodocidae (7 species) and the Terebellidae (7 species). The Shannon-Wiener index was lowest (1,7 bits) in the intertidal area, particularly in stations nearest the cages. This low value is characteristic of a polychaete community in muddy sediments (Nicolaidou & Papadopolou, 1989) and of polluted communities (Ros et al., 1990; Salas, 1996). Despite the relative abundance, the results show that in the sampling sites nearest the cages, sedimentivorous families Pisionidae, Maldanidae and Chrysoptalidae are present. This indicates a possible situation of greater organic enrichment than at other sites.