THERMAL ECOLOGY AND STRESS 353 



time, two explanations appear to be plausible. First, it is conceivable 

 that elevated temperature in thermally altered locations may act as a 

 selection force for a more virulent strain of A. hydrophila. Although 

 it is indirect and not unequivocal, there is some evidence to support 

 this hypothesis. Hazen, Fliermans, and Esch (manuscript in prepara- 

 tion) have shown serological and immunological differences in 

 certain strains of A. hydrophila isolated from fish, alligators, and Par 

 Pond water. This line of study has promise and is being pursued. 

 There appears to be a more sound explanation, however, for the 

 relation between temperature and red-sore disease in the reservoir. 



Since 1967, more than 10,000 bass have been captured in Par 

 Pond (Gibbons et al., in press). The weight— length relationships of 

 each of these fish were recorded, and the body condition, or 

 K-factor, of each individual was determined. Body condition is a 

 measure of individual fitness, or physical well-being (Carlander, 

 1969). Parenthetically, it is important to note that mark-recapture 

 studies of many of the same 10,000 bass indicate that the vast 

 majority (>98%) appear to remain locally within discrete home 

 ranges of the reservoir and, consequently, do not move long distances 

 (Gibbons and Bennett, 1971; Quinn et. al., 1978; Hazen and Esch, 

 1978. When K-factors for all bass are shown seasonally (Fig. 13), 

 a distinct pattern emerges. Generally, maximum body condition 

 occurs in winter, with lowest conditions in summer. The exceptions 

 during the fall of 1975 and in the fall of 1976 are due either to 

 variations in reactor activity or to differences in sample sizes in 

 thermally altered and ambient locations. 



When body conditions of bass from ambient and thermally 

 altered locations are compared (Fig. 14), individuals from thermally 

 altered areas are, in general, less fit than those from ambient 

 locations. Exceptions to this trend occur in the fall of 1975 and 

 again in the winter of 1977. Even when these data are included with 

 those from all other seasons, there are significant differences in body 

 conditions of bass taken in thermally altered and ambient locations. 



Because of the within-season variability in body condition and 

 infection percentage, it was surmised that there could be a 

 relationship between body condition and the probability of a bass 

 being infected with A. hydrophila. Comparing the infection percent- 

 ages for each 0.2-unit K-factor subclass between 1.0 and 3.0 

 (Fig. 15), we can see clearly that bass with the lowest body 

 conditions are most likely to be infected. The decline in infection 

 percentages begins between K-factors of 1,8 and 2.0 and continues to 

 decrease as body conditions improve. It is interesting to note that 

 virtually all bass with body conditions below 2.0 are without any 



