Stress and Body Condition in a Population of Largemouth Bass: Implications for Red-Sore Disease

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Abstract
The body conditions, K = 105(weight, g) .div. (standard length)3 and various hematological characters were examined for largemouth bass (M. salmoides) taken from Par Pond, a reservoir heated by effluent from a nuclear production reactor at the Savannah River Plant near Aiken, South Carolina, USA. Largemouth bass with K less than 2.0 had significantly lower (P < 0.05) hematocrits, Hb concentrations, total red blood cell counts, total white blood cell counts and lymphocyte fractions, and significantly higher granulocyte fractions and cortisol concentrations than those with K greater than 2.0; monocyte, thrombocyte and reticulocyte fractions were not different between the 2 K-factor groupings. When data were pooled, all blood variables except the reticulocyte fraction were significantly correlated with K. Hematocrit, the lymphocyte fraction and cortisol concentration account for 20.5% of the variation in K. These data support a previous hypothesis that elevated water temperature promotes stress. Stress within the Par Pond largemouth bass population may play an important role in the epizootiology of red-sore disease caused by the gram-negative bacterium, Aeromonas hydrophila.