Masters Theses

Mark S. Tisa

Date of Award

6-1981

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Richard J. Strange

Committee Members

J. Larry Wilson, Charles C. Coutant, Douglas C. Peterson

Abstract

One hypothesis to explain adult striped bass (Morone saxatilis) mortalities observed from 1972 to 1977 during the summer months in Cherokee Reservoir was that fish were being abnormally crowded by temperature preference and low dissolved oxygen into a limited number of cool, well-oxygenated creek or spring fed coves (refuge areas) contaminated by zinc and cadmium from the watershed. The goal of this study was to determine if the adverse environmental conditions (high temperature and low dissolved oxygen) were the cause of striped bass mortalities either directly or in combination with zinc and/or cadmium. Zinc and cadmium residues in muscle, liver, and kidney tissues and hematology of adult striped bass from Cherokee were compared to striped bass from Norris and Watts Bar Reservoirs. Also, liver histology of Cherokee striped bass was compared to Norris striped bass.

Even though there were significant differences in tissue residues among seasons (summer 1979, spring 1980, summer 1980) in Cherokee Reservoir as well as among the three reservoirs during the same season (spring 1980), all the concentrations were well below those reported for fish exposed to maximum non-harmful concentrations of zinc and the lowest potentially harmful concentration of cadmium and were in the same approximate range typically reported for fish tissues. It is therefore believed that in at least the last two years, zinc and cadmium in the tissues of striped bass from Cherokee Reservoir have not been harmful to the fish.

Hematological studies revealed statistically significant differences for several blood characteristics between seasons (spring and summer 1980) for striped bass from the same reservoir (Cherokee) and among the three reservoirs (Cherokee, Norris, Watts Bar) during the same season (spring 1980). These differences, however, are believed to be due to normal seasonal variations, different collection times during the spring season, and water quality differences among the reservoirs. No pathology was associated with any of the differences in blood characteristics.

Liver histology showed a high degree of heterogeneity for vacuolation, vascular stasis, and dilated and engorged sinusoids within livers of individual fish from both Norris and Cherokee Reservoirs. There were no signs of any necrosis and no pathology was associated with any of these findings.

Since July 1, 1979 when this study began, there have been no unexplained striped bass mortalities in Cherokee Reservoir. This investigation found no evidence of pathology and the striped bass collected from Cherokee in the last two years appeared as healthy as the ones from Norris and Watts Bar Reservoirs. Perhaps the most plausible explanation for the cause of striped bass mortalities in Cherokee Reservoir was high temperature and low dissolved oxygen with inadequate carrying capacity in the refuge areas to support the entire population those years. The author recommends continued stocking of striped bass but perhaps in fewer numbers so that adequate space in the refuge areas is assured during the critical summer months.

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