Lake Michigan fishery is like the stock market.

Over the last 50 years, the Lake Michigan salmon and trout fishery has often borne similarities to the stock market.

There have been significant downturns, such as when bacterial kidney disease hit chinook salmon in the 1980s.

Yet wise allocation of resources, such as four stocking reductions, have helped maintain a reasonable balance between predator and prey fish.

And for most of five decades, the fishery has paid dividends to anglers with some of the finest freshwater fishing on the planet.

But like an industry running thin on raw materials, in recent years the lake’s ecosystem has been squeezed by invasive mussels and high numbers of predator fish. The double whammy of bottom up and top down forces has resulted in historical lows of forage fish, according to scientists.

There are two major themes facing Lake Michigan anglers and fisheries managers in 2017, said Willie Fetzer, Great Lakes specialist for the Department of Natural Resources.

“One is the level of risk stakeholders are willing to tolerate in terms of managing the fishery and the ratio between predators and prey,” Fetzer said. “And the other is, since the lake’s ecosystem is complex and changing on a yearly basis, we need to evaluate the entirety of the information and not solely focus on what fits any individual desire for the system.”

Fetzer made his comments June 7 at a Lake Michigan fisheries meeting in Milwaukee.

To illustrate his points, he showed a graph of historical fluctuations in the Dow Jones Industrial Average.

Similar rises and falls have been seen in key indicators of the lake’s salmon, trout and prey fish, especially alewives.

As has been widely reported over the last year, the U.S. Geological Survey found a record low biomass of alewives in its 2016 bottom trawl surveys.

The work has been conducted since 1973 at index sites throughout the lake.

Other key forage fish, including rainbow smelt and bloater chubs, also were down.

The dwindling stocks of prey fish caused the Lake Michigan Committee of the Great Lakes Fisheries Commission to recommend a cut in chinook salmon stocking.

The committee set a 2017 goal of reducing stocking by 900,000 “chinook salmon equivalents.”

Fisheries managers in Michigan, Illinois and Indiana opted to reduce chinook plants, while the Wisconsin DNR bucked the committee’s advice and cut brown trout and lake trout.

For 2017, Wisconsin’s plan was to stock 812,270 chinook (same as 2016), 452,867 coho (same), 300,000 lake trout (712,377 in 2016), 340,000 steelhead (269,512) and 362,000 brown trout (727,014).

The June meeting in Milwaukee, and another the next night in Cleveland, were designed to present the latest information on the fishery and collect public input as the DNR makes stocking plans for 2018.

Presentations were given by DNR fisheries personnel, including Fetzer, Cheryl Masterson, Tom Meronek and Nick Legler, to update anglers on the latest findings. The 2016 data was better than many expected. For starters, the condition of adult salmon was quite good relative to recent years and more young alewives were observed than in 2015.

In 2016, the lakewide average weight of an age 3 female chinook was 18.1 pounds, up from about 12.5 in 2015 and above the 30-year average of 15.4 pounds.

Using a model with 2016 data inputs, including the documented weight of salmon, fisheries biologists adjusted upward the 2015 estimate for alewife biomass in the lake.

In 2015, the lakewide alewife biomass was set at 37 kilotonnes. In 2016, based largely on the heavier salmon observed in the lake, the 2015 alewife biomass was recalculated at 78 kilotonnes.

As a result, the predator-prey ratios for 2015 and 2016 were reduced to 0.05 and 0.075, respectively.

The target is 0.05; 0.10 is considered the upper limit and a sign of too many predator fish and too few forage fish.

Despite the revisions, the biomass of alewives in Lake Michigan is a concern, Legler said. A crash of alewives about a decade ago in Lake Huron led to a significant drop in chinook numbers.

Among other not-so-good news: Lake Michigan charter boats had a lower catch rate last year. The targeted chinook salmon harvest per hour in 2016 was about 0.10 fish, below the 30-year average of 0.16.

Brad Eggold, DNR regional fisheries manager, wrapped up the meeting by fielding questions and taking comments.

Several attendees wanted the brown trout stocking numbers to be increased in the future.

Eggold said if the agency increases brown plants, another species would have to be reduced.

“This is one of the biggest challenges, managing the expectations of all the different groups,” Eggold said. “We’re at a point where we know the lake has changed and will likely continue to change, so we plan to keep monitoring it as closely as possible and working with the stakeholders to make adjustments as necessary.”

A public comment period is open through July 8 on Lake Michigan salmon and trout stocking.

The Lake Michigan Fisheries Forum also will host a meeting in late August or early September to present additional data.

Another comment period will be held in September.

The DNR will then consider all the public input and scientific data with the goal of making its final 2018 stocking plans by Oct. 15.

Comments may be sent by email to dnrlakemichiganplan@wisconsin.gov or by mail to Brad Eggold, Department of Natural Resources, UWM-GLRF-SFS, 600 E. Greenfield Ave., Milwaukee, WI 53204.