Estimating Incision Healing Rate for Surgically Implanted Acoustic Transmitters from Recaptured Walleye

To understand surgical incision healing rates of Walleye implanted with acoustic transmitters, photographs of recaptured fish provided by anglers and commercial fishers were examined for incision closure, inflammation, and presence of sutures. Walleye (n= 1079) from reef and river spawning populations in Lake Erie and Lake Huron were implanted with acoustic transmitters during spring spawning events from 2011 to 2015. Surgeons used 2 to 3 polydioxanone monofilament absorbable sutures (PDS II – size 3/0) to close the incision. Out of 319 recaptured Walleye, 48 had useful photographs.  Incision sites were 95% closed by 113 days post-release.  Inflammation at the incision declined during the first 78 days, but remained detectable at low levels, (i.e., < 20% of the area), for up to 1,139 days. Sutures were expelled serially over a protracted period, and the probability of observing at least one suture in a recaptured fish declined below 50% after 547 days (95% C.I.= 416-783 days). Our results emphasize that these sutures remain in free ranging fish past the time when they were beneficial to incision healing. More work is needed to identify sutures or other incision closure methods that facilitate healing while absorbing in a reasonable time period (e.g., several months).