Author
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Mitchell, Andrew |
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Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only Publication Acceptance Date: 7/12/2004 Publication Date: 7/26/2004 Citation: Mitchell, A.J. 2004. Reasons for the occurrences of massive trematode infestations in cultured fish [abstract]. In: Annual Eastern Fish Health Workshop. p. 32. Interpretive Summary: Technical Abstract: The onset and rapid growth of pond aquaculture, the loss of wet lands, the resurgence of aquatic bird populations and the importation of exotic snails, and parasites have lead to massive trematode infestations in cultured fish. Starting in the late1950s a fish farming industry (developed primarily in ponds) sprang up throughout the southeastern United States. The farm ponds provided areas where fish were concentrated, where aquatic snail populations could grow uninhibited (and they did) and an ideal habitat for aquatic birds seeking a fish or other pond inhabitant to eat. In this same period, there was much land development eliminating wetlands previously inhabited by large populations of aquatic birds. In the late 1970s, aquatic birds species began to stage a comeback from an apparent three decades of dramatic reduction in numbers (perhaps the effects of highly residual pesticides in the environment, blamed for their demise, began to lessen). The birds began to frequent the limited available habitat that now included fish ponds. By the mid 1980s, hundreds of aquatic birds were lining the banks of ponds. With the bird's return a situation ripe for trematode infestation was born; the snail, fish, and bird hosts were numerous and in close proximity. The missing element was the trematodes; actually they were there but apparently in small numbers. Time, one of the last elements, was required to build up the number of native parasites that would cycle through the hosts. Additionally, imports added at least one exotic snail complete with an exotic trematode that could be transmitted to many native fish species. Movement of the exotic snails by man and exotic trematodes by snail, fish, and birds, resulted in the spread of trematode infections. As a result of some or all of the above mentioned factors, massive infestations of the trematodes Posthodiplostomum minimum, Bolbophorus damnificus, Centrocestus formosanus and Clinostomum marginatum, to name some, were reported in pond raised fish throughout the southeast. In the case of the exotic trematode (Centrocestus formosanus), wild fishes were also found with massive infections. |
