By Dan O’Keefe, Michigan State University Extension
Lake Michigan supports a world-class recreational fishery for five species of salmon and trout and offers more localized fishing for nearshore fish like walleye, yellow perch, and smallmouth bass. It is a complex ecosystem with a long history of exotic invasions and losses of native species, but the lake continues to produce fish that are accessible to boat, shoreline and river anglers.
The current fisheries are maintained in part by efforts to control non-native sea lamprey and stock salmon and trout that eat another non-native fish, like the alewife. Much has been written concerning the birth of the salmon fishery and the many positive and negative effects that alewife have on native species. The bottom line is that managers now balance the number of predatory salmon and trout in Lake Michigan to avoid having too many or too few alewife in the lake and to maintain fisheries.
The lake’s fisheries and their management are shared between Michigan, Wisconsin, Illinois, Indiana, and five tribal governments represented by the Chippewa Ottawa Resource Authority. The Lake Michigan Committeeof the Great Lakes Fishery Commission is comprised of resource managers representing the five fishery management agencies. Decisions regarding the lake’s fisheries are made by consensus among these parties and their current decision process involves a problem that is more serious than it may sound: Too many predators for the available prey.
Modeling work by Dr. Michael Jones and Dr. Iyob Tsehaye of the Quantitative Fisheries Center at Michigan State University suggests that current stocking levels have a good chance of leading to the collapse of alewife in Lake Michigan. If managers continue with status quo stocking for the next twenty years, they could expect a 23% chance of low alewife biomass and a 35% chance of low Chinook salmon weight that could lead to starvation and disease outbreaks.
To reduce these risks, the Lake Michigan Committee is considering several options for reducing stocking levels. Chinook salmon stocking was reduced lakewide by 25% in 2006 and the results of that cut are viewed as largely positive. Chinooks reproduce successfully in many rivers, so reductions in Chinook stocking alone may not be enough to limit risks to acceptable levels. Reductions in stocking of other trout and salmon species may further help to ease the pressure on bait fish such as alewife.
However, these other species provide unique fisheries that many anglers cherish. Steelhead provide river fishing opportunities almost year-round, brown trout are popular with small-boat and pier anglers in spring and lake trout can provide reliable fishing for big-lake trollers when other species are not available. In addition to angling interests, the lake trout are native to Lake Michigan, whereas the other stocked salmon and trout are not. Lake trout numbers are maintained entirely through stocking and there is some concern that cutting lake trout stocking would not be consistent with rehabilitation goals.
Where does this leave us? Fisheries managers are asking for public input on recommendations for future lakewide stocking efforts that will limit the risk of a collapse in the fishery. Educated opinions regarding which species to cut are important because the ultimate goal of balancing predators and prey can be attained in a variety of ways. One strategy that has not been used in the past is a feedback policy that would allow for higher stocking rates when alewife are plentiful.
Details regarding feedback policies and other stocking options under consideration will be presented to the public on April 14, 2012. The meeting will be held at Lake Michigan College in Benton Harbor, Mich. A full agenda and options for online participation are available on the Michigan Sea Grant website. Presentations from Jay Wesley of the Michigan DNR and Dr. Michael Jones of MSU‘s Quantitative Fisheries Center are also available online. These provide an overview of past and current status of Chinook salmon and forage fish, as well as in-depth discussion of the modeling process.