Use of coded-wire and visible implant elastomer tags for marine stock enhancement with juvenile red snapper Lutjanus campechanus

Abstract

As part of a stock enhancement research project in the Gulf of Mexico, we evaluated optimal tag placement sites, retention, and detection in hatchery-reared juvenile red snapper Lutjanus campechanus (46–110 mm standard length) with coded-wire tags (CWT) and visible implant elastomer tags. Coded-wire tags were implanted in nose cartilage, left cheek muscle, the nape, dorsal musculature, and the caudal peduncle. Three weeks after tagging, all implant locations tested showed tag retention over 97% except for those implanted in the dorsal musculature (90%). No additional tag loss was found between 3 and 6 weeks after tagging regardless of implant location or fish size. We selected the nape musculature for larger-scale tagging because of high tag retention and ease of tagging. Retention of CWTs in the nape after 6 months was 99% ( n = 285). Visible implant elastomer (VIE) tags were implanted in muscular and fin tissue of juvenile snapper and retention rates were ≥95% (after 6 weeks) for all implant locations except for anal fin muscles (87% tag retention). In a separate study, 6 months after tagging, fish size-at-tagging and the number of VIE marks implanted in the caudal fin significantly influenced tag retention (two-way analysis of variance, P = 0.026). After experimental stock enhancement releases, divers 17–20 m deep, found that VIEs in caudal fins were highly visible, but those in the nose area were difficult to see due to pigmentation over the tags and fish orientation. Tag color influenced tag visibility and red and orange elastomer tags were the most visible among eight colors tested (red, orange, yellow, green, pink, black, blue, and purple). Divers commonly confused green elastomer tags for yellow, and sometimes confused red, pink and orange. No color confusion occurred when similar colors were observed side-by-side however.