Tracking Change in Lake Michigan’s Fisheries

The SV Steelhead is operated by the Michigan DNR out of the Charlevoix Fisheries Research Station. The trawler has been used for scientific sampling of Lake Michigan’s fisheries and deep water habitats since 1968.Lk_MI_Walleye_3_cropped_small

To develop this video essay, Nature Change joined the crew for a day of sampling during this spring’s annual lake-wide fisheries assessment. The sampling process keeps the crew busy on the water for weeks with sampling locations ranging from southern Lake Michigan to the far north.

Readily merged with surveys from other states, this annual lake-wide survey plays a key role in understanding the characteristics of Lake Michigan fisheries.  In recent years, sampling data have documented dramatic changes in the fisheries as well as the entire ecosystem attributed to the arrival and explosive growth of new invasive animals and plants. As described by DNR Fisheries Biologist, Jory Jonas, these rapid ecosystem changes make management decisions extremely difficult and complex.

Jory_Jonas_1
Jory Jonas, Fisheries Biologist Specialist Michigan Department of Natural Resources.

The introduction of lampreys and the Atlantic herring called Alewife resulted in huge changes to the fisheries in the 1950s and 60s. For example, Lempreys and overfishing nearly wiped out the native Lake Trout populations. Eventually, Pacific Salmon were introduced to control the exploding alewife population and create new commercial and sport fisheries.

 

Over the last 25 years or so, the arrival of zebra mussels and the round goby from Eurasia – along with many other nonnative plants and animals have completely changed conditions for fisheries managers – once again. As widely reported, the alewife population has declined dramatically as have the number of salmon. However, recently gathered data suggests that Lake Trout are doing much better now. In fact, Jory believes there is a recovery of the native trout populations underway now, after decades of frustration.

Interestingly, one reason for this trout recovery may be the round goby itself. There is evidence that by eating gobies, trout are overcoming a long-time deficiency in Vitamin B1 or thiamine. This is a key nutrient needed for successful reproduction.

According to Jory, “nothing is either all good or all bad. The are winners and losers when you have this level of change going on.” For

Round Goby (neogobius melanostomus)
Round Goby
(neogobius melanostomus)

example, she notes that since the invasion of round gobies, sculpin have been completely missing from nearshore areas. But trout, bass and other high-level predator fish are doing well with goby as the prey fish.

Unfortunately, the exploding populations of quagga mussels in Lake Michigan (another invasive species)  is causing still more disruption and change in the Lake Michigan ecosystem. Filtering out plankton and displacing other organisms that feed small fish, the quagga is having impacts that are only now being fully felt.

Jory Jonas believes that Lake Michigan is beginning yet another dramatic ecosystem change. As she puts it, “We’re going to get another reboot with the quagga mussels out there.”

Dreissena_bugensis
Quagga Mussel (Dreissena bugensis)

“We’re not managing for these introductions; we’re managing despite them,” Jory says. Until we stop these introductions of invasive species, she says, “we’re going to be in this game of responding and trying to understand after the fact. And that’s a horrible position to be in as a manager.”

 

2 thoughts on “Tracking Change in Lake Michigan’s Fisheries

  1. In the 1950’s and the 1960’s the Great Lakes were loaded with Smelt! You ask any Fisherman that fished or netted for Smelt during the 1950’s and 1960’s what happen to the smelt and they will tell You that the Alewife consumed all the food that smelt lived on thus drastically reduced the Smelt population

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