Masters Theses

Date of Award

5-2006

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Richard J. Strange

Committee Members

Mark S. Bevelhimer, Charles C. Coutant, Marshall S. Adams

Abstract

To address Clean Water Act regulations concerning reduction of fish impingement at water intakes (316b) I investigated approaches for identifying moribund or impaired shad under stressors of cold shock and reduced ration. In preliminary experiments, we determined the initial point of loss of equilibrium (LOE) for threadfin shad to be 7.2°C and for gizzard shad to be less than 3.5°C. I exposed shad to increasing levels of cold shock and reduced ration and then measured physiological and behavioral responses. Gizzard and threadfin shad exhibited reduced swimming performance at temperatures slightly above LOE. Cortisol and chloride showed a linear correlation with swimming performance in gizzard shad but not threadfin shad. Cortisol increased as a response to cold shock and declined after an acclimation period at a cold temperature. The expected change in serum chloride in relation to cortisol occurred in threadfin shad but not gizzard shad. I observed few differences in swimming performance and physiological indicators among ration treatments for either species. However, field observations suggest that the duration of reduced ration I used, 21-days, was not sufficient to reproduce the condition of shad in late winter. The nutritional status indicators, hematocrit and condition factor, demonstrated a declining trend. These indicators could be measured easily in the field to determine the susceptibility of shad if further testing shows a relationship with decreased swimming performance. The results of this study indicate that the term moribund does not apply well to all shad impacted by natural environmental stressors and its application should be reevaluated. Threadfin and gizzard shad are susceptible to impingement before moribundity occurs. The use of physiological indicators as predictors of impingement susceptibility appears promising.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS