Long‐Term Retention and Visibility of Visible Implant Elastomer Tags in Brook Trout

Abstract

Understanding how juvenile brook trout Salvelinus fontinalis from different sources contribute to fishable populations would be facilitated by a batch mark that could be applied to early life stages and be retained and visible throughout a fish's life. We evaluated visible implant elastomer (VIE) as a long‐term batch mark for juvenile brook trout in hatchery and lake environments. Visible implant elastomer material was injected into the postocular eye tissue of 2,350 age‐0 brook trout. Marked fish were stocked into three lakes, and an additional group was held in the hatchery. Tissue dissections revealed that VIE tag retention was 100% in both environments after 970 d. Tag visibility in hatchery fish examined under indoor fluorescent light was greater than 95% through 585 d, then dropped to 55–70% between 700 and 900 d. Tag visibility in lake fish examined under outdoor sunlight was 50–72% at 400 d and 0% at 959 d. When these same fish were observed in dark conditions with blue‐filtered light and amber glasses, tag visibility was 75% for hatchery fish at 970 d and 100% for lake fish at 959 d. The high retention and increased visibility when viewed in dark conditions with blue‐filtered light demonstrates that VIE tags are a suitable long‐term batch mark for juvenile brook trout.

Comparison of three methods for marking a small floodplain minnow

“…Our results with VIE tags in Oregon chub are consistent with other studies demonstrating high survival, tag retention, and visibility in small-bodied fish (e.g., [31][32][33][34]). However, success with VIE tags appears to vary with body location and species.…”

“…Furthermore, we have since observed these tags in the field 407 days after marking (unpublished observation, B. Bangs). VIE tag retention of juvenile brook trout Salvelinus fontinalis reared in an indoor hatchery and lake environment was 100% after 970 days [33]. The visibility of the tag in hatchery reared fish was >95% through 585 days, but decreased to 55-70% between 700 and 900 days.…”

“…In the lake environment, visibility of the VIE tag was 50-70% through 400 days, and 0% at 959 days. Josephson et al used blue filtered light and amber glasses in dark conditions to increase tag visibility, and observed 100% retention for lake reared fish at 959 days and 75% retention in hatchery fish at 970 days [33]. This suggests that UV illumination may increase tag visibility and recognition in long-term field studies.…”

Fish movement in an Atlantic Forest stream

“…Mortality, stress by handling and tag losses are among the causes of low recapture rates (Porto et al, 1999;Smithson, Johnston, 1999 Josephson et al, 2008;Carvalho-Souza et al, 2010;Soula et al, 2012) as well as low mortality caused by tagging procedures (e.g. Riley et al, 1992).…”

Comparing tagging strategies: Effects of tags on retention rate, mortality rate and growth in hatchery-reared juvenile meagre, <em>Argyrosomus regius</em> (Pisces: Sciaenidae)

“…However, one constraint of these studies is the loss of both tags, so a "permanent tag" such as PIT, CWT or VIE has been used for comparison (Brennan et al 2005, Josephson et al 2008, Rude et al 2011. In this study, the experiment conducted with the T-bar anchor tag, internal anchor tag and VIE had two goals: to seek an alternative to T-bar anchor tag (in the case of the internal anchor tag), and to select a "permanent tag" for future experiments under natural conditions (in the case of VIE).…”