Study: Released walleyes caught through ice have high survival rates

Our recent great walleye hatches are a blessing for those who chase these delectable finny creatures.When fishing for them, we must often release undersized fish or extras if we continue to "fun-fish" after our limit has been reached.Catch-and-release fishing only makes sense if the majority of the fish live through the process of being hooked, pulled to the surface, handled while removing the hook, then released back into the water.Picture-taking adds time that the fish is outside its watery element. Other adverse health effects that can befall a landed fish include gas bladder expansion (barotrauma), hooking wounds to gill filaments and internal bruising. In the winter, sub-freezing temperatures can lead to the chances of the surface of the eyes, gills or skin freezing while out of the water.A study on Lake Nipissing, Ontario, monitored 24-hour mortality rates of walleyes caught and released while ice fishing. Comparisons were made between mortality rates of fish caught by jigging vs. tip-ups and between the use of different barbed hook types.The scientific paper by William Twardek and eight other co-authors appeared in the American Fisheries Society's, North American Journal of Fisheries Management, 38:159-169 (2018).Jigging was much more effective, catching 0.21 walleyes per hour vs. 0.04 fish per hour using tip-ups.With tip-ups, the catch rate using circle hooks was 0.13 fish/hour, compared to J-hooks (0.03) or treble hooks (0.05). In total, 260 walleyes were landed, with 113 caught by jigging and 147 caught on tip-ups.When a fish was landed, the data recorded included the length of the fish, depth of the capture, how deeply the fish was hooked, whether there was visible barotrauma, and the surface temperature of the fish's gill flap.Within a 45-second period of time, the fish was marked using a unique combination of fin and (fin) spine clips before being placed into a sunken holding pen for observation and mortality calculations.A total of only 18 walleyes died during the study, leading to an overall mortality rate of 6.9 percent. While passive fishing resulted in 9.8 percent mortality of the 147 walleyes, and active fishing resulted in the loss of 2.8 percent of the 113 fish, the results are not statistically significant, due to the small sample size.Observers noted that deep-hooking occurred much more often with tip-ups (50.4 percent) than by jigging (9.3) and were highest in J-hook designs and lowest in treble hook designs. However, there were no statistically significant differences in mortality rates between the hook designs or how deeply they were in the mouth.In fish that were deeply hooked, colder water temperatures led to slower metabolism, less blood loss and higher survival rates (85 percent) than expected. In fish with deeply swallowed hooks, better outcomes occurred when the line was cut compared to handling the fish longer to extract the hook.Surprisingly, during this study, delayed mortality rates were not significantly different between fish that showed barotrauma (23 percent) vs. those without symptoms when the other observations were factored in.There are normally higher mortality rates of walleyes with deeper capture depths and higher water temperatures during catch-and-release tournaments. The wildlife agencies in Ohio and several other states no longer allow catch-and-release walleye tournaments. The fish taken in most Lake Erie walleye tournaments these days are donated to local soup kitchens.The study showed that winter fishing mortality is comparable to summer fishing mortality, which has been documented to range from 0.8 percent to 31 percent, with an average of 5 percent.The 6.9-percent mortality rate in this case was lower than reported in earlier winter studies of catch-and-release mortality on Lake Nipissing walleyes of 19 percent or rates of 12 percent for sauger, 10 percent for lake trout and 1-to-33 percent for northern pike (depending upon hook type) elsewhere.With the colder temperatures now upon us, ice fishing is finally looking possible yet for this winter. Ice fishermen wishing to catch and release healthy walleyes should use jigging techniques instead of tip-ups, play the fish quickly, handle them gently, reduce the amounted time that the fish is exposed to sub-freezing temperatures and cut lines when the hooks are deeply embedded.Because jigging for walleyes is so productive here, tip-ups are less popular on Lake Erie than elsewhere.Anglers wishing to use tip-ups while catch-and-release fishing should consider that even though circle hooks had higher catch rates, treble hooks lead to fewer deeply hooked fish.A recent study showed that jigged walleyes are more often hooked less deeply than those caught on tip-ups.