Health of Fish Impinged on Cooling-Water Intake Screens
Type of DegreeThesis
Fisheries and Allied Aquacultures
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Fish health evaluations were made between impinged and reference fish collected at and in the vicinity of Plant Barry (Mobile River, Mobile County, Alabama) from April 19, 2005, until May 19, 2005, and again from September 26, 2005, until November 2, 2005. The four species of fish investigated were threadfin shad (Dorosoma petenense), channel catfish (Ictalurus punctatus), blue catfish (Ictalurus furcatus), and freshwater drum (Aplodinotus grunniens). Evaluations were based on body weight-length and liver weight-body weight indices, gross external lesions, and pathogens. Impinged threadfin shad, blue catfish, and freshwater drum weighed significantly less (7-30%) during the spring, and impinged threadfin shad and freshwater drum weighed significantly less (12-32%) during the fall when compared with reference fish of equivalent lengths. Additionally, lesions were significantly more common for all species of impinged fish than for reference fish during the spring (14-73%) and for species except threadfin shad during the fall (25-64%). Lesions observed included necrotic gill filaments, eroded fins and fin bases, ulcers, skin depigmentation, and hemorrhaging. Liver, trunk kidney, and the periphery of lesions on gills and skin were sampled for bacteria. Flavobacterium columnare was detected in a significantly greater percentage of impinged fish than in reference fish during the spring (13-61%) and fall (16-74%). The protozoan parasite, Ichthyobodo necator, was also observed at a significantly higher prevalence during the spring (50%) and fall (30%) in impinged freshwater drum. The weight of blue catfish (10.1% and 18.4%) and channel catfish (12.6% and 9.5%) collected from October 24, 2005, until October 27, 2005, from the intake pit at Plant Barry was significantly greater at equivalent lengths compared with fish of the same species collected from both the river and impinged population during the fall. Threadfin shad collected from the intake pit weighed 12.9% less than impinged threadfin shad and 11.5 to 35.4% less than river threadfin shad at equivalent lengths. External lesions were significantly higher in impinged blue catfish and channel catfish collected during the fall (39-64%) compared with similar species sampled from the intake pit. Aeromonas spp. were significantly higher in impinged blue catfish (18%) compared with intake pit fish. The prevalence of F. columnare was significantly higher in impinged blue catfish, channel catfish, and threadfin shad (33-74%), collected during the fall, compared with fish from the intake. Aeromonas spp. prevalence was significantly higher in river blue catfish and channel catfish (12.3-12.7%) compared with fish from the intake. However, threadfin shad from the intake had a higher prevalence of I. necator (10%) compared with threadfin shad from the river.