Major disease encountered in controlled environment culture of tilapias in fresh- and brackishwater over a three-year period in Arizona
1988
Ligthner, D. | Redman, R. | Mohney, L. | Dickenson, G. | Fitzsimmons, K. (Arizona Univ., Tucson, Arizona (USA). Environmental Research Lab.)
A number of disease adversely affected cultured populations of tilapias reared in high density recirculating systems at the University of Arizona's experimental controlled environment fish culture station. The tilapia cultured were Oreochromis mossambicus, O. aureus, a golden hybrid of O. mossambicus x O. urolepis horrorum, a Taiwanese red strain of O. mossambicus and Tilapia zillii. Gill hyperplasia, presumably due principally to chronic ammonia and nitrite toxicity, was common in recirculated fresh- and brackishwater culture systems. Skin and gill parasitism by the protozoa Trichodina sp., Epistylis sp., Ichthyobodo sp., Apiosoma sp. and Ambiphrya sp. were also common and were occasionally associated with mortalities. Bacterial septicemias were observed on several occasions. The principal bacterial isolates from affected fish reared in freshwater were Aeromonas hydrophila and Edwardsiella tarda, while Vibrio sp., A. hydrophila, and an Aeromonas sp. were the most important organisms isolated from infected fish reared in brackishwater. Fungal infections observed included superficial Saprolegnia infections on eggs and fry and a granulomatosis renal infection by an imperfect fungus of the genus Paecilomyces. Of interest was the occurrence of tumor-like lesions of the kidneys in two senescent adult golden tilapia.
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