Assessment of PIT Tag Retention and Post-Tagging Survival in Transformer-Phase Sea Lamprey

Passive Integrated Transponder (PIT) tags have been used to document and monitor the movement or behavior of numerous species of fishes. When initiating a study using PIT tags, it is important to document immediate and post-surgery survival, as well as tag retention. We evaluated PIT tag retention and survival of sea lamprey (Petromyzon marinus) transformers in a controlled environment for 25+ d. Sea lamprey transformers (n=191) were anesthetized, 12 mm PIT tags were inserted surgically into the body cavity, then individuals were monitored. Tagged lamprey were held in a small tank for 24h post-surgery to monitor initial tag retention and immediate survival, and then moved to a 1.2m circular tank where the lamprey were monitored thereafter. Survival was 100% at 24h post-tagging, and ≥89% at 25d post-tagging, compared to 95% survival of untagged lamprey. Tag retention was 100% at 24h post-tagging and ≥98% at 28d post-tagging. Ninety-nine percent of tagged transformers >145mm (n=151) survived, and 71% of tagged transformers <145mm (n=40) survived. Based on these results, sea lamprey transformers longer than 145mm are recommended for studies using PIT tags.