A PRELIMINARY-STUDY OF PARASITES AND DISEASES OF PERCH IN AN INTENSIVE CULTURE SYSTEM

The recent development of intensive rearing of European perch Perca fl uviatilis in warm water effluents revealed important pathological prob lems. This study gives a preliminary overview of parasites and disease s encountered in experimental perch farming. No virus has been recorde d since the beginning of the experiments in 1993. By contrast, mass mo rtality caused by bacterial disease alone or associated with other pat hogens were frequently observed. The main identified bacterial species were: Aeromonas sp., A. veronii, A. hydrophila, Streptococcus sp., St aphylococcus sp., Vibrio fluviatilis and Enterobacter agglomerans. Pro tozoans were the most common parasites observed on cultured P. fluviat ilis. High mortality rate due to Ichthyobodo necator and Trichodina sp . may take place at different stages of perch rearing. In contrast, th e infestation by Ambiphrya sp. and Heteropolaria sp. was size- or age- related; these two ciliates infested perch weighing < 1 g and > 20 g, respectively. In spite of the presence of other parasites such as Icht hyophthirius multifiliis, Hexamita spp., Gyrodactylus sp. and Argulus sp. in the rearing system P. fluviatilis does not appear to be affecte d. Further abnormalities or diseases inherent to intensive culture sys tems are also described.