Stress caused by the 'mark-recapture' method to Coregonus albula (L)

The aim of this study was to establish if capture and marking caused stress to C. albula , and if a 'mark-recapture' method was suitable for the estimation of a population of C. albula . The blood lactate and glucose levels and the liver and muscle glycogen content were determined during the initial handling and subsequent recovery of the fish in the autumn and spring.
The blood lactate content did not increase to the critical level. Usually the values were distinctly less than 100 mg %, but the blood glucose content increased throughout the whole experiment (24 h) until it reached 250 mg %. The glycogen content in liver and muscle decreased. The liver glycogen of female C. albula was below 0·3 % in autumn, while the values for males were 3–5 %. In spring, the corresponding values were about 0·5 % in both sexes. During handling, the critical period was when the glycogen reserves in the liver became negligible, and female C. albula in autumn had the greatest risk of dying because of their low liver glycogen content.
Spring seemed to be a better season for marking than the autumn. A steady increase in blood glucose indicated there was also stress in spring and the marking time in both seasons should be less than two hours.