Behavioural impacts of MS-222 and electro-immobilization on wild fish assessed using a whole lake telemetry system

To immobilize fish for the surgical implantation of electronic tags, tricaine methanesulfonate (“MS-222”) and electrical currents (“electro-immobilization”) are commonly used. Despite the abundance of literature examining the physiological side effects of these immobilization methods, few studies have examined whether using MS-222 or electro-immobilization during tagging alters the behaviours of fishes in the wild. To do so, we used a whole-lake telemetry system to compare recently tagged largemouth bass ( Micropterus nigricans) and northern pike ( Esox lucius) immobilized with either MS-222 or transcutaneous electrical nerve stimulation (TENS) to previously tagged (i.e., recovered) controls. Despite species-specific alterations in behaviour for the first 72 h after tagging, the behaviours of both largemouth bass and northern pike were similar to controls within ∼100–200 h of tagging, regardless of the immobilization technique used. Our results support the censoring of data from at least the first week post-tagging to avoid bias from the tagging process, as well as the use of TENS as a viable alternative for MS-222, given the similarity of recovery patterns among treatment groups.