Aquacutture and Fisheries Management 1993. 24, 101-108 Protozoan parasites of wild and cultured sea bass, Dicentrarchus labrax (L.), from the Mediterranean area p. ALVAREZ-PELLITERO, A. SITJA-BOBADILLA & A. FRANCO-SIERRA Instituto de Acuicultura Torre de la Sal (CSIC), Ribera de Cabanes, Torre la Sal, Castellon, Spain Abstract. In a parasitic survey of wild and cultured sea bass, Dicentrarchus labrax (L.), thirteen protozoan species were found. Ectoparasites included two ciliates {Trichodina spp.), one dinoflagellate {Amylodinium sp.) and one zooliagellate {Cryptobia sp.). Endoparasites were represented by members of Apicomplexa {Hemogregarina sp.. Eimeria spp.). Microsporea (unidentified species) and Myxosporea {Myxobilatus sp,, Ceratomyxa spp,. Sphaerospora dicentrarchi, Sphaerospora testicularis). Myxobilatus sp., Eimeria spp. and the microsporean were exclusively found in wild fish, whereas Amyloodinium sp. and Hemogregarina sp. were only detected in culturedfish.Data on prevalence and intensity of infections and on the location in the host are provided. The potential importance of protozoan parasites for sea bass culture is discussed. Introduction The increasing interest in cuiture of commercial marine fish, such as Mediterranean sea bass, Dicentrarchus labrax (L.) has emphasized the importance of pathological processes. Protozoan parasites of sea bass are relatively unknown. Apart from our own data, which include descriptions of some species and the study of their population dynamics (Sitjil-Boba- dilla & Alvarez-Pellitero 1990, 1992, 1993; Alvarez-Pellitero & Sitja-Bodadilla 1993), the only information available deals with occasional studies (Paperna & Baudin-Laurencin, 1979; Siau & Sakiti 1981; Daoudi & Marques 1987) or references to outbreaks in the case of Amyloodinium sp. (Paperna 1980). Information regarding cultured fish was reviewed by Paperna (1984). The present study analyses the protozoan fauna found in a parasitic survey of sea bass from a wild population and from different culture systems. The potential importance of these parasites for sea bass culture is also discussed. Materials and methods Fish The following groups of sea bass were studied: Wild fish (W). 101 individuals, 3+ to 5+ years, sampled monthly at the River Ebro Delta during 1986. Correspondence; Dr P. Alvarez-Pelliterc. Instituto de Acuicultura Torre de la Sal, Ribera de Cabanes, 12595 Torre la Sal. Castellon, Spain. 101