Retention of visible implant alphanumeric tags in adult Walleye

Abstract

In 2010, Northwest Marine Technology introduced a more rigid visible implant alphanumeric (VIA) tag that substantially improved the tag loading and injecting process. To achieve these improvements, VIA tag size and composition was modified, thereby potentially influencing previously examined VIA tag retention rates on Walleye Sander vitreus. Effects of total length (TL), sex, and days post-tagging on retention of VIA tags injected underneath the lower mandible of adult Walleye were evaluated from 2012 to 2016. Walleye (n = 2455) collected from natural lakes in Iowa were measured, sexed, and injected with identical VIA tags on each side (left and right) of the lower mandible. Of 366 Walleye recaptured up to four years post-tagging, 241 had both tags; the remaining fish had retained only one tag. Overall, tag retention adjusted for fish that lost both tags (n = 14) was 80% (607 of 760). Retention of VIA tags was not influenced by sex, TL at time of marking, or number of days post-tagging and did not substantially differ from previously examined large-format VIA retention rates. In studies requiring high tag retention in Walleyes, VIA tags injected into the clear tissue underneath the mandible should be avoided.

Long-Term Retention of Passive Integrated Transponder Tags Injected into the Pelvic Girdle of Adult Walleye

“…Walleye were collected from a chain of lakes in northwestern Iowa during April 2015 via short-term (2-hr) gillnet sets, transported to a state fish hatchery, and held in cement raceways using the same procedures as described in Meerbeek et al (2013) and Meerbeek (2017). After Walleye were processed by hatchery staff, male and female Walleye were placed in separate raceways and workers then measured (total length [TL]; nearest 2.54 mm) each fish and checked for an existing Visual Implant Alphanumeric (VIA) tag.…”

“…All tagging was performed in April 2015 by the same individual then all PIT-tagged Walleye were released back to the lake of capture. Walleye were recaptured during annual gill netting surveys conducted from March-April 2016-2019 (see Meerbeek et al 2013 andMeerbeek 2017). Recaptured Walleye each year were scanned using the handheld tag reader to check for a PIT tag.…”

“…al (2012) injected PIT tags into the subcutaneous musculature between the pelvic fins of adult Walleye Sander vitreus as a secondary mark used in a multijurisdictional jaw tag retention study in Lake Erie and observed high PIT tag retention rates for this location (98%). Walleye mark-recapture studies in Iowa have used visual implant tags injected in the clear tissue on the lower mandible, but recent estimates of tag retention in this location have been less than desirable (i.e., 76-80%; Meerbeek et al 2013;Meerbeek 2017). Implanting PIT tags in the dorsal musculature of Walleye has resulted in high tag retention rates (99.5%; Weber and Flammang 2017), but since Walleye are a major sport fish targeted for consumption, managers wanted to avoid this location for marking to reduce angler-PIT tag interactions.…”