Impacts of External and Surgery-Based Tagging Techniques on Small Northern Pike Under Field Conditions

Abstract

In Northern Pike Esox lucius negligible effects of external tags on growth and survival have commonly been reported, but no studies exist for age-0 fish. We tested the impacts of fin clipping, PIT tags, and three external tags (T-bar anchor, opercular, and streamer tags) on age-0 Northern Pike in a pond. We also examined the impacts of surgically implanted transmitters on small adult Northern Pike in a natural lake. The loss of PIT tags was lowest among all tags and close to 0%. Of the external tags, T-bar anchor tags performed best. Loss of these tags was initially low (on average 5.7% after 195 d) increasing to about 20.0% by 520 d posttagging. Tagging-induced mortality of a few percent was present in all tags tested within the first 195 d posttagging in the pond environment but not present afterwards. The PIT tags, fin clips, and external tags did not affect the growth or condition of surviving fish. Surgically implanted transmitters reduced the growth of small adult Northern Pike with total lengths <480 mm, but no effects were found for larger individuals. We conclude that PIT tagging is the most suitable marking technique for age-0 Northern Pike. If external visibility is required, T-bar anchor tags are also useful, as long as tagging-induced mortality and tag loss rates are accounted for at the analysis stage. Our study raises a cautionary note about surgically implanted transmitters in small adult Northern Pike, as they may negatively affect behavior and fitness.

Received March 27, 2013; accepted November 26, 2013

ACKNOWLEDGMENTS

We thank A. Türck, F. D. Johnston, M. E. Beck, M. Morkritzki, E.-M. Cyrus, and J. Hilsberg for their help and assistance during data collection in the field, and P. Freudenberg for providing photographs. In addition, we would like to thank C. Skov and M. S. Allen for discussions that led to the study design, F. D. Johnston and C. T. Monk for a technical edit, and R. B. Pierce and one anonymous reviewer for constructive feedback. Funding for this research was granted by the German Ministry for Education and Research within the program on Social–Ecological Research and the project Besatzfisch (www.besatz-fisch.de) (Grant # 01UU0907), by the Deutsche Bundesstiftung Umwelt (grant # AZ 20007/924), and by the project Adaptfish by the Gottfried-Wilhelm-Leibniz-Community (www.adaptfish.igb-berlin.de). The experiments were approved through an animal care permit (23-2347-15-2010) granted by the Ministry of Environment, Health and Consumer Protection Brandenburg, according to the German Animal Protection Act.