A QUANTITATIVE AND QUALITATIVE COMPARISON OF INTESTINAL FLORA OF STRIPED BASS (MORONE SAXATILIS WALBAUM) IN AN ESTUARINE AND A COASTAL MARINE ENVIRONMENT; VIRULENCE OF SELECTED INTESTINAL ISOLATES AND EFFECTS OF HEAVY METALS ON DISEASE SUSCEPTIBILITY (FISH)
Monthly intestinal samples from a total of 130 randomly selected striped bass taken from an estuarine or coastal marine environment from May through October 1981 resulted in isolation of 365 bacterial isolates of which 96% (361) were asporogenous Gram-negative rods. Total viable bacteria in striped bass intestines increased during the summer, but bacterial numbers in fish taken from the coastal marine environment. The predominant bacterial groups recovered were members of the Enterobacteriaceae and genera Aeromonas, Pseudomonas, Vibrio, Alcaligenes, and Flavobacterium. Aeromonas hydrophila was most abundant in striped bass taken from the estuary and Vibrio was most in fish taken from the coastal marine environment. The high percentage of pathogens found in the intestines of apparently healthy striped bass and the virulence of these pathogens indicates a potential for epizootics. Static waterborne challenge of striped bass with a moderately virulent strain of Flexibacter columnaris in hard water was used to determine effects of environmentally realistic concentrations of arsenic, lead, copper, selenium, and cadmium on infectivity. Striped bass exposed to mixtures of these metals for 7 days showed neither overt signs of toxicity nor evidence of histopathologic changes. Four and 10-fold concentrations of average environmental levels of these metals consistently protected striped bass against experimental F. columnaris infection and were not toxic to F. columnaris in medium or in water. When striped bass were challenged with F. columnaris and exposed for 5 days to individual metals at 10X concentrations, copper was found to be nontoxic and to provide protection against infection. Cadmium was similarly protective, but 20% of test fish died of apparent metal toxemia. Lead and selenium were neither protective nor toxic. Arsenic clearly enhanced infectivity. Striped bass exposed only to F. columnaris showed 24.5% mortality, whereas fish exposed to the bacterium and arsenic showed mortality three times as high. This study involved short-term exposure of young-of-the-year striped bass to metals in hard water. Care should be taken in extrapolating these results to other systems involving different life stages of striped bass in environments of different water chemistry.
MACFARLANE, RICHARD DONALD, "A QUANTITATIVE AND QUALITATIVE COMPARISON OF INTESTINAL FLORA OF STRIPED BASS (MORONE SAXATILIS WALBAUM) IN AN ESTUARINE AND A COASTAL MARINE ENVIRONMENT; VIRULENCE OF SELECTED INTESTINAL ISOLATES AND EFFECTS OF HEAVY METALS ON DISEASE SUSCEPTIBILITY (FISH)" (1984). ETD Collection for Fordham University. AAI8506346.