By Gabe Gries
Science in Action—While survival of walleyes caught and released during the open-water season has been studied in-depth, little is known about post-release mortality of walleyes released by ice anglers. Researchers recently evaluated post-release survival of walleyes caught and released by ice anglers at Lake Nipissing, Ontario.
Angling was conducted in January and February using active and passive techniques. The active fishing method was jigging with1/4-to 3/8-ounce Northland Buck-Shot and Macho Minnow spoons and Cabela’s jigheads baited with dead emerald shiners. Spoons had treble hooks. Anglers used medium-to light-power rods with 6-pound-test monofilament. Passive angling methods included tip-ups and setlines with #4 Gamakatsu Octopus and circle hooks baited with wild emerald shiners and weighted with a 1/4-ounce sinker. All hooks in the study were barbed. Walleyes were caught at water depths ranging from 20 to 41 feet to assess the effects of barotrauma on post-release mortality.
Upon capture, the hook was removed, and hook location and signs of barotrauma noted. For walleyes hooked deeply in the esophagus, gills, or tongue, the line was cut or the hook was removed with pliers. Air exposure didn’t exceed 45 seconds. After hook removal, fish were placed in nets suspended in the water column and mortality was assessed after 24 hours.
Angled walleyes averaged 14 inches. Overall post-release mortality after 24 hours was 6.9 percent. A higher percentage of walleyes were deeply hooked when caught using passive (50.4 percent) than active (9.3 percent) techniques, and deeply hooked walleyes had higher mortality (14.8 percent) than shallow hooked fish (3.0 percent). Mortality of walleyes caught using active (2.8 percent) or passive (9.8 percent) techniques wasn’t significantly different, nor was it for fish caught on J-hooks, circle hooks, or treble hooks. Air temperature and depth at which fish were caught didn’t have a significant effect on mortality. Mortality was higher for deeply hooked fish when hooks were removed (22.6 percent) compared to when the line was cut (11.1 percent).
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Results from this study indicate a relatively low rate of mortality within the first 24 hours for walleyes released after ice angling. A high proportion of walleyes were caught using small baited hooks on passive lines, resulting in frequent deep-hooking.The researchers note that while mortality from deep-hooking was modest in their study, larger hooks should be tested to see if they reduce deep-hooking. Overall, they say walleyes were resilient to capture and handling, including handling in air and on ice prior to release, and even fish that showed signs of barotrauma had high survival. They suggest it may be prudent for anglers to cut the line on deeply hooked walleyes intended for release.
*Twardek, W. M., and 8 co-authors. 2018. The post release survival of walleyes following ice-angling on Lake Nipissing, Ontario. N. Am. J. Fish. Mgmt. 38:159-169.
