Quantitative Measurement of Calcein Fluorescence for Non-lethal, Field Based Discrimination of Hatchery and Wild Fish
David A. Crook, Damien J. O’Mahony, Bronwyn M. Gillanders, Andrew R. Munro, and Andrew C. Sanger
Abstract.—Recent studies have described nonlethally detectable techniques for externally marking fish with fluorescent compounds such as calcein. We describe the use of a portable fluorometer for the nonlethal quantitative measurement of fluorescence in calcein marked golden perch Macquaria ambigua. The results demonstrate that calcein marked fish could be unambiguously identified more than 2 years after marking when held in the laboratory; the body mass of the fish had increased from 0.8 to 1.3 g (median 1.0 g) to 6–44 g (median 11.1 g) over this period. Similarly, marked fish released into the wild at approximately 1 g were detected at up to 18 months postrelease and 66 g in weight. However, some deterioration in the detectability of the external marks was apparent in the larger fish recaptured from the wild. Based on these findings, we suggest that the technique has the potential to provide a practical and objective means of discriminating hatchery and wild fish under field conditions.