By EAMON DEVLIN
Capital News Service
LANSING – When you reel in the salmon of your dreams, people may ask how big or what kind it was.
It’s unlikely someone will ask where it was born.
But that’s what researchers at Michigan State University are now asking to better understand how many Chinook salmon move from Lake Huron to Lake Michigan.
So, where are the fish born?
For researchers, the answer lies in a stone in the fish’s ear. The concentrations of chemicals found in these stones – technically called the otolith, which function like human ears – can be used like a fingerprint linking the salmon to its stream of birth.
The stones are made of calcium carbonate. The largest, known as the sagittae, is the focus for researchers.
“It picks up different chemicals and a lot of heavy metals from the environment,” said Alex Maguffee, an MSU master’s student in fisheries and wildlife, who is researching the question with Michael Jones, a fisheries biologist at the university.
These chemicals and metals appear in different concentrations in different streams, which is how researchers can link a specific fish to a specific birthplace.
The next question: Why are the salmon moving?
Chinook salmon eat alewives, an invasive fish to the area. Alewife populations in Lake Huron are declining. So, too, are the Chinook salmon populations, reports the Great Lakes Fishery Commission.
The salmon themselves aren’t native to the lakes. They were introduced by state departments of natural resources initially to control the alewife population, but the salmon have turned into a lucrative sport fishing industry, according to the Great Lakes Environmental Assessment and Mapping Project.
Salmon have begun to move from Lake Huron into Lake Michigan in search of alewives, Maguffee said.
“We know that they move – we just don’t know how much,” he said. “The whole purpose of the experiment is to make sure we are stocking the correct number of salmon.”
The study will help determine how many fish government agencies in Michigan, Wisconsin and Minnesota should stock in their lakes. Adding too many fish would limit their size, and too few would mean fewer to catch, Maguffee said.
The Michigan Department of Natural Resources is stocking fewer Chinook salmon in both lakes Huron and Michigan based on the smaller salmon caught in recent years.
The Minnesota and Wisconsin departments of natural resources also report that they’re cutting back on the salmon they stock in Lake Michigan.
Maguffee and other scientists are creating a mathematical model to predict the movements of fish from one lake to the other. Researchers can then estimate what proportion of fish will migrate based on the original number of fish stocked, Maguffee said. They can also estimate how many salmon born in Lake Huron end up in Lake Michigan.
Eamon Devlin writes for Great Lakes Echo.