Visible Implant Elastomer Color Determination, Tag Visibility, and Tag Loss: Potential Sources of Error for Mark–Recapture Studies

Abstract

Errors in visible implant elastomer (VIE) color determination may exert stronger influences on mark–recapture data quality than poor tag visibility and tag loss. I applied individual VIE tags to 567 wild long-snouted seahorses Hippocampus guttulatus using four fluorescent colors (red, orange, green, and yellow). Given VIE tag data were compared with tag data recorded by observers as they released recently tagged individuals back to initial capture locations. During releases, 13.3% of VIE tags were incorrectly read, primarily because of confusions between orange and red markings and between green and yellow markings. Tags were partially invisible in 5% of released individuals; yellow and green markings were the least visible. Whole or partial tag loss was 2.3% within 14 months of tagging. The ability to correctly determine VIE tag colors or detect markings varied among observers and according to the VIE tag color employed, skin color, and shade of the skin color (e.g., light versus dark green). Observer experience did not influence ability to correctly determine VIE colors or detect tags. Pilot studies should precede mark–recapture studies employing multiple VIE colors to identify strategies for reducing confusion among colors in addition to evaluating tag visibility, tag loss, and tag effects on life history rates.