Effects of different tagging protocols on survival, growth, and tag retention in juvenile least cisco Coregonus sardinella

Abstract

Passive integrated transponder (PIT) and T-bar anchor tags are often used in fisheries evaluations. To collect unbiased data, tags must not alter behavior, growth, or survival and have high retention rates. We examined tag retention, growth, and survival of age-2 juvenile least cisco Coregonus sardinella over a 60-day experiment following handling, anesthesia, tagging, and recovery using PIT and T-bar anchor tags. Fish were assigned to one of 12 treatment groups (20 fish per group), with individuals first assigned to one of three tagging treatments (internally implanted PIT tag, externally attached T-bar anchor tag, no tag [control]). Tag treatment groups were next assigned to a pre-handling anesthesia treatment (clove oil or no anesthetic) and a post-handling recovery treatment (elevated [10 ppt] saline or ambient [3 ppt] saline solution). Tag retention for least cisco was greater for fish that received PIT tags (100%) compared to T-bar anchor tags (25–45%). The majority of T-bar anchor tag loss (50%) occurred between days 25 and 45 of the experiment. Fish in all treatments exhibited positive growth, with no differences among treatments for specific growth rates, Fulton condition, or survival (80–100%). Most mortality (13 of 18 fish) occurred by day 5 of the study. The lowest survival (80%) occurred for fish that were not anesthetized, received PIT tags, and recovered in a 10-ppt saline solution. Our results indicate that T-bar anchor tags are sufficient for short-term studies (<30 d) involving least cisco, but PIT tags are preferred for longer evaluations (>30 d) of this species.