Short-term survival and growth of American Eel elvers marked with visible implant elastomer tags

Abstract

Objective: Visible implant elastomer (VIE) tags are commonly used as a cost-effective tool for marking small fish, making them valuable in mark–recapture studies. It is crucial to quantify the impact of tagging procedures on fish survival to address inferential bias in mark–recapture studies. We assessed marking-related mortality and growth in American Eel Anguilla rostrata elvers in a 40-day laboratory experiment, following VIE tag application. Methods: There were 500 elvers (80–149 mm) that were divided into four treatment groups and one control group. Treatment groups were tagged with two tags in three body locations (anterior, central, posterior on left bilateral side) or with two tags in all three locations, while the control group remained untagged. Eels were retained in experimental tanks, and mortality rates were compared. Result: The VIE tagging did not significantly affect survival, which was 90.9% across all treatment groups and 92% for the untagged control group; nor did it affect growth. Conclusion: The application of VIE tags on various body parts should be a safe and effective method for marking American Eel elvers.