Three fisheries biologists were recognized for their work on a far-reaching study of Lake Huron's changing food web, including two with the Department of Natural Resources' Alpena Fisheries Research Station.
The DNR's Fisheries Division gave Ji He and Dave Fielder the Tanner and Tody Award for their leadership in the study, and securing grants to make it possible. Partner Jim Bence, who works at Michigan State University, was recognized as well. They were part of an effort involving contributions from numerous agencies to answer a handful of key questions about predator-prey relationships in the lake. Invasive zebra and quagga mussels outcompeted the filter-feeding plankton alewives ate, and the disappearance of that fish had major consequences for the lake's fisheries.
Jim Johnson, DNR Fisheries research biologist in charge of the Alpena Fisheries Research Station, said the fact two of the recipients work in the station affirms employees there are striving to provide the best possible data for management decisions.
"This award recognizes that this station really is doing cutting-edge work, and that's cool," he said. "Being a research office, that's what we're supposed to be doing."
The award is named after former DNR fisheries Chief Howard Tanner and his assistant, William Tody. The two came up with the idea of introducing a Pacific salmon fishery to the Great Lakes in the 1960s, Johnson said.
A lot changed after alewives left; on one hand, Chinook salmon loved to eat alewives and suffered greatly when they vanished, Fielder said. On the other, they're something like junk food, since they caused thiamine deficiency in lake trout, devastating their natural reproduction rates. And while biologists knew some predator fish were eating invasive round gobies, their population was a mystery.
So in 2005, He started working on a new study focusing on how the predator-prey balance and relationships had shifted, according to a summary Johnson wrote about the study. He used grant money from the Great Lakes Restoration Act and Commission and information from the DNR's independent and fisheries survey, as well as from commercial and tribal fishers. In 2010 he got a second grant from the Great Lakes Fisheries Commission to include walleyes, Chinook salmon and whitefish.
He also secured funding from the excise tax levied on hunting and fishing gear, Johnson said. These three grants allowed the DNR to bring on short-term workers, spend more time in the lab and fund students and staff at MSU. All this effort was aimed at finding out what predators were eating after the change, and how much of a forage base was out there for them. Biologists also were interested in identifying which species had switched, and how the change affected fish life history.
Ji He estimated lake trout and whitefish populations with the help of the United States Geological Survey, Bence looked at Chinook salmon and Fielding estimated walleye population, catches and survival rates. Chuck Madenjian of the USGS helped considerably with the whitefish portion, and many other agencies contributed as well, including in Ontario.
By gaining a better understanding of how many predators were in the lake, and how well they were faring, Fielder, He, Bence and others learned more about the lake's forage base, Johnson said. They were able to determine that, while the round goby is a problematic invasive species, certain predators like lake trout are eating them in droves while others aren't. Predator fish are apparently keeping them in check, and when gobies are factored into the equation, Lake Huron's lower end of the food web is doing better than previously estimated.
"(Gobies) kind of the only game left in town," he said. "Alewives are gone and rainbow smelt are way down."
Beyond that, the model will allow the DNR to better determine how the health of one species affects the other. It's a more system-wide approach, rather than looking at one particular species at a time. Now the challenge is to keep the model updated and continue to assess the situation in the lake.
"This gives us some really clear clues as to what Lake Huron's fishery can be in the future," Fielder said.