Anchor and visible implant elastomer tag retention by hatchery rainbow trout stocked into an Ozark stream

As part of a study to evaluate the stocking of rainbow trout Oncorhynchus mykiss in an Oklahoma Ozark stream, we tagged 2,542 hatchery-reared rainbow trout (123-366 mm total length) with individually numbered Floy FD-68B anchor tags and visible implant fluorescent elastomer (VIE) tags. We experimentally stocked double-marked rainbow trout into a small northeastern Oklahoma stream from November 2001 to March 2002 and resampled them monthly from December 2001 to October 2002 by electrofishing. Anchor tag retention was 91% through 6 months, and VIE tag retention was 96% through 6 months despite extensive handling of fish within 24 h of tagging. Based on the ease of application, high visibility, and high retention observed in this study, we recommend the use of VIE tags as a batch mark in similarly sized, similarly pigmented fish. The retention of VIE tags was slightly higher than that of anchor tags, and cost per fish was less for VIE than for anchor tags. However, VIE tags would have limited utility if numerous individual tags are necessary; therefore, we recommend anchor tags as individual marks in similarly sized salmonids. Retention for both tag types was relatively high and could be corrected for when estimating population parameters from tagging data.