Can trophy walleyes be kept without hurting their population?

For many years, it has been well known that there is an annual fall migration of large walleyes into the Sandusky Sub-Basin, near Huron. They are there to take advantage of the massive accumulation of gizzard shad that are attracted to the remaining warm water temperatures that they crave.As walleye fatten up on these slow-moving targets, which flounder as water temperatures drop closer to freezing, it marks a time when some of the heaviest trophies of the year can be caught.To date, whenever fishermen ask if keeping big female walleyes harms the population in large bodies of water, the reply offered by fisheries biologists here and elsewhere in the Midwest has been that there is no evidence that it does.This is why Ohio and most other states allow year-round fishing and allow anglers to choose whether to keep the "hens" that they catch while fishing any month of the year.Using slot limits to harvest only medium-size fish, allowing only one fish over a certain size or prohibiting fishing during the spawning season are often social, not biological, decisions that come from people concerned about overharvesting the resource.However, some recent scientific studies have caught the attention of fisheries biologists who monitor spawning success and populations.Dr. Chris Vandergoot, with the U.S. Geological Survey in Sandusky, co-authored a report that was published in 2016. It suggests that in Lake Erie, larger maternal walleyes may have a better ability to produce larger eggs and contribute significantly to the spawn in years when there is a long, cold winter.These larger eggs have more lipids available, which gives the fry a longer period of time to consume the yolk-sac before having to forage for external food sources.Better eggs and corresponding survivability of the offspring can create a larger year-class of fish in years when foraging conditions are favorable for locating adequate food.In walleyes, yellow perch, lake trout and Atlantic cod, the authors conclude that "management practices which protect large, old females could indeed improve stock stability and productivity."Dr. Stu Ludsin and his graduate students at Ohio State's Aquatic Ecology Lab have independently shown that with yellow perch, long, cold winters lead to later spawning, which allows more thorough egg development and maturation. This often leads to a better match with the timing of emerging planktonic food sources later in the spring.Climate change can make long, cold winters less common in Lake Erie, thereby reducing spawning success of yellow perch over time, he concludes.Some Australian researchers at Monash University in Melbourne found that in 95 percent of the species that they studied, big, old females existed with egg counts exceeding numbers that would be expected, simply given the fish's length.Some of these fish, dubbed "superspawners", produced hundreds of times more eggs than younger, yet sexually mature spawners.They also showed that some species of older fish produce eggs that are "extra nutritious" and have better survival than those usually produced by younger fish.Climate change was also cited by these researchers as a concerning factor, as many fish grow slower in warmer water temperatures, making big, superspawners rarer and more important to protect.Other fisheries biologists discount the significance of older fish, claiming that the total biomass of the eggs that are deposited are equally important as ensuring larger ones are present.As proof that the current, overall conservative harvest quotas are not causing populations to become overfished, Lake Erie chronically has lots of old, large walleyes in the population, but none have been labeled here as "superspawners."Ohio State research a decade ago showed that in Lake Erie, all sizes and ages of walleyes produce quality eggs. Thus, there is no (biological) justification for trophy walleye restrictions for the Ohio angler fishery, according to Lake Erie program administrator Travis Hartman.He speculated that a couple of factors may be responsible for this year's huge walleye and above-average perch hatches. One was that the long winter helped, as the research suggests. The other is that walleye populations have historically peaked during periods of high-water cycles, as we are experiencing now, perhaps by placing the spawning reefs at ideal depths.The regulations that are already in place are designed to keep walleye populations healthy, so don't feel guilty about taking home your daily limit. But, there is no rule that requires anglers who catch trophy walleyes to keep them all, either. Let your conscience decide.An angler holds a nice Lake of the Woods walleye. (Brad Dokken/Grand Forks Herald/TNS)