THE FATE OF A YEAR CLASS

THE FATE OF A YEAR CLASS

From the Minnesota DNR 2001 Fisheries Newsletter. Edited by Harlan Fierstine,
Area Fisheries Supervisor and Pat Rivers, Large Lake Specialist (Leech Lake).

As anglers are gearing up to fish Leech Lake, the fate of a fish population is being determined below the water's surface. Walleye and other fish encounter obstacles from egg to adult, and people can help by protecting natural habitat in the lake and surrounding watershed. Many factors must come together to produce a strong year class of walleye. First of all, a good number of eggs must hatch. A spawning female walleye commonly lays thousands of eggs each year. To survive, these eggs must be quickly fertilized by a male walleye. Poor spawning habitat, predation, disease, weather events, and many other factors can kill many of the developing eggs before they hatch. Once the eggs hatch, the walleye fry must soon find food to live and grow. If food is abundant, more fry will survive; if food is scarce, more will die. Predation and competition between fry for food influence this stage of year class development. Growth of these young of the year fish is crucial to their survival. If growth is good, by the end of August young of the year walleye, now called fingerlings, are nearing 6 inches in length. Larger fingerlings in good condition have a better chance to survive during the winter months when the food supply decreases. Typically, after the second growing season, the abundance of a walleye year class has been established. The relative strength of this year class depends on how well this group of fish weathered their early life. Fortunately, Leech Lake has an abundance of suitable walleye spawning habitat and adequate numbers of spawning fish. Leech Lake has the most consistent walleye reproduction of Minnesota's large walleye lakes, and the current population is made up of a number of strong year classes. However, any lake, even large lakes like Leech, is susceptible to human induced habitat problems. Human activity and careless development within the watershed of Leech Lake can degrade water quality and habitat necessary for healthy fish populations. Altering a shoreline and removing upland or aquatic vegetation can accelerate erosion and increase the amount of sediment in the water. This sediment load can be deposited over spawning areas used by walleye and other species and negatively affect year class production. Although a shoreline development project may appear small to the individual, a number of these small projects can have cumulative effects on fish populations. Habitat protection is truly the best long-term strategy to give young walleye a helping hand and to provide quality angling opportunities for the future.