Retention of Large‐Format, Soft Visible Implant Alphanumeric Tags in Walleye

Abstract

AbstractWe evaluated the effects of fish length, fish sex, and number of days posttagging on retention of large‐format, soft visible implant (VI) alphanumeric tags that were injected underneath the clear tissue on the lower mandible of Walleyes Sander vitreus. We also evaluated whether the direction of insertion or the application of surgical‐grade tissue adhesive to the tag incision site would affect tag retention. Adult Walleyes were collected with gill nets from natural lakes in Iowa during spring and then were transported to a hatchery, where they were measured, sexed, and tagged. One worker injected 752 Walleyes (mean TL = 21.8 in; SE = 0.16) with two identical VI tags; each side (left and right) of the lower mandible received one tag. Incisions were dried with a cloth, and tissue adhesive was applied to one of the two tag injection sites. Walleyes were released back into the lake and were recaptured with gill nets and by anglers. Of the 129 Walleyes recaptured up to 5 years posttagging, 80 fish (62%) had retained both tags and the remaining 49 fish had retained one of the tags. Retention adjusted for fish that lost both tags (n = 8; probability = 0.09) was 58% (80 of 137). Tag retention was significantly related to fish size at the time of tagging, as smaller fish lost more tags. Consequently, males (mean TL = 20.5 in; SE = 0.39) were more likely to lose tags than females (mean TL = 24.3 in; SE = 0.26). Insertion direction, adhesive application, or the number of days posttagging at recapture did not influence VI tag retention. We recommend that in studies requiring high tag retention in Walleyes, the injection of large‐format, soft VI tags into the clear tissue underneath the mandible should not be considered.Received February 16, 2012; accepted October 3, 2012