By Howard Meyerson
PENTWATER – As Lake Michigan states prepare to cut Chinook salmon stocking by 50 percent on Lake Michigan, researchers are looking closely at the growing number of wild fish that swim there. Determining their abundance will prove increasingly important to Great Lakes fish managers.
Chinook salmon now reproduce naturally in Michigan shoreline streams from Charlevoix south to the Muskegon River. Those naturalized populations add substantially to the Lake Michigan fishery, according to a Michigan Department of Natural Resource study that found wild fish made up 63 percent of the 2010 Chinook salmon year class in the lake, a total of more than 5 million wild smolts.
“We don’t know exactly where they come from, or how many of them come from Canada, but we thought the level of natural reproduction would be more variable. The lack of variability has been a surprise,” said Randy Clarmunt, with the Michigan Department of Natural Resources Charlevoix Fisheries Station.
Clarmunt recently addressed the Ludington Charter Boat Association at an annual Michigan Sea Grant workshop. He described the findings of a 2006 to 2010 study that examined more than 5,000 Chinook salmon collected from anglers fishing in tournaments all over Lake Michigan.
The study showed 53 to 56 percent of the one-year-old Chinooks caught between 2006 and 2009 were wild. Wild two-year-olds made up 62 to 69 percent of the catch while three-year-olds made up 61 to 66 percent of the catch.
“If natural reproduction were to jump to 90 percent we would have 15 to 20 million wild smolts in the lake and that would devastate the prey fish community within a year.”
–Randy Clarmunt, MDNR Fisheries
Wild salmon have become a hot-topic in fisheries circles. Chinook salmon was once a put-and-take fishery that relied on state hatcheries. If fisheries managers wanted more, they grew them and stocked them. But as the data from mass-marking studies accumulated over the years, fish managers became increasingly aware that wild fish were turning up in angler catches. Further studies have since confirmed that finding – and that the percentage of wild fish has increased.
That development, combined with record low numbers of alewives in recent years, due to the influx of invasive mussels filtering out food alewives need to survive, led to the 2012 decision by Lake Michigan states to reduce hatchery stocking in an attempt to assure that salmon have enough to eat.
Wild salmon is a mixed blessing, according to Lake Michigan fisheries managers. Their
presence reduces the need for hatchery stock and associated costs, but they also introduce a wild-card into planning.
“Natural fish are better for the system and are more adaptable and in some ways that is good,” said Jay Wesley, the DNR’s southwest Michigan fisheries coordinator. “We are asked by anglers to control the conditions in the lake and with wild fish out there we are losing control.
“In the past, I could plant more fish and anglers would end up with more in the box, but now we are at the mercy of natural reproduction. A bad reproductive year could affect the population.”
Too many wild salmon can also be a problem, he said. There is only so much food for them to eat.
“If natural reproduction were to jump to 90 percent we would have 15 to 20 million wild smolts in the lake and that would devastate the prey fish community within a year,” Clarmunt said. “We would cut back on stocking, but we might not have a fishery left.
That scenario is unlikely, according to Clarmunt. He and others think the available spawning habitat has been saturated.
That wild fish make up a higher percentage of two and three-year-old fish in the lake does not come as a surprise to Clarmunt. He has two theories about why it happens.
Hatchery fish are bigger when they are stocked which gives them a head-start, he said. They grow faster and die earlier than wild fish, which grow and mature more slowly.
The second theory is that wild salmon are migrating into Lake Michigan from Canadian waters in Lake Huron. Researchers roughly estimate that Canadian waters produce 14 million wild smolts every year. Just how many make to Lake Michigan is unknown.
Rick Clark, the retired head of DNR fisheries research, who now conducts research for the Quantative Fisheries Center at Michigan State University where he is an adjunct professor, theorizes that wild Canadian salmon could be showing up in Lake Michigan.
Wild salmon behave the same as hatchery salmon, according to Clark. And coded wire-tag studies in the 1990’s and 2000s showed a dramatic increase in the number of Lake Huron stocked salmon that got caught in Lake Michigan.
“Coded wire tag data showed that five to six percent of the hatchery fish stocked in Lake Huron showed up in Lake Michigan in the 1990’s,” Clark said. “Between 2000 and 2008 that rate increased greatly to 20 percent.”
Those same studies also showed that the percentage of wild fish in Lake Huron rose rapidly from 15 percent in the 1990’s to 80 percent in 2000. Some of those fish may also be travelling into Lake Michigan, Clark said.
New research being proposed would examine chemical isotopes that are absorbed in salmon otoliths, a small structure in the head. Those isotopes are unique to certain waters. If the research is funded, work would begin next year to begin identifying where wild fish are born: whether in Lake Michigan, Lake Huron, The Georgian Bay and potentially different streams.
Computer modeling determined the need to make salmon stocking cuts on Lake Michigan in 2013, but those models, he said, do not account for wild fish coming in from Canada.
“Wild fish are becoming more and more important to the fishery,” Clark said. This (new research) would give us a pretty comprehensive look at where adult salmon are coming from in Lake Michigan.”
Copyright © 2013 Howard Meyerson