POPULATION-DYNAMICS OF SPHAEROSPORA-DICENTRARCHI SITJA-BOBADILLA-ET-ALVAREZ-PELLITERO, 1992 AND S-TESTICULARIS SITJA-BOBADILLA-ET-ALVAREZ-PELLITERO, 1990 (MYXOSPOREA, BIVALVULIDA) INFECTIONS IN WILD AND CULTURED MEDITERRANEAN-SEA BASS (DICENTRARCHUS-LABRAX L)

The population dynamics of Sphaerospora dicentrarchi and S. testicularis, myxosporean parasites of sea bass (Dicentrarchus labrax), was studied in different groups of cultured and wild fish. S. dicentrarchi prevalence was higher for wild fish (100 %) than for cultured ones (70.5 %). Infection levels increased with host age and there were no significant sex differences in cultured fish. Among parasitized organs, the gall bladder and intestine registered the highest infection levels in wild and cultured fish. A progressive increase in infection levels of S. testicularis was observed in cultured males during the spawning season in four consecutive periods. The evolution of the percentage of the different parasitic stages is pointed out. The infection seems to be related to water temperature and gonadal maturation.