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A Study on Coho Salmon Sep 25, 2019 11:41 am #25345

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Hello All my Fellow Lake Michigan Anglers,

My name is Maxwell Morgan I am a research scientist on Lake Michigan and an avid fisherman out of Milwaukee. Currently I am starting a (pretend) research project to study the recent trends in Coho Salmon. This is in no way being used for any regulatory use or decision making. It is purely for my interest and passion for Great Lakes fisheries and a class project. I am currently getting my masters degree at UWM School of Freshwater Sciences and this is a topic that has always fascinated me.

It has been heard on the grapevine that in early spring Coho salmon have bellies full of "shrimp." These shrimp are called Mysis. Since the disappearance of the
Diporeia (iaglr.org/jglr/release/37/37_1_9-17.php), most likely due to the invasive mussels, these shrimp have become a much more important food source for not only alewife, but Coho alike.

It is my understanding that in early spring Coho predate on these shrimp heavily. Then at some point, as they move clockwise around the southern basin of the lake and the water warms up, they switch to a predominately Alewife diet. It would be a huge help to me if anyone has any pictures of Coho gut contents or knowledge/advice on this.

I personally think of myself as a fisherman first and a scientist second. I have always advicated for the cooperation of these two groups. You guys are out there all the time and have a much more practical knowledge of the lake. Please help me to bridge this gap! All your feedback is greatly appreciated. I hope you all have had a chance to cash in on the fall fishing run. My personal email is This email address is being protected from spambots. You need JavaScript enabled to view it. if you are more comfortable with that.

Thanks again
Max

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A Study on Coho Salmon Sep 26, 2019 8:29 pm #25356

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I hope that many will chime in for you. It has been my experience that the coho can be inshore one day and offshore the next in deep water feeding on the Mysis. I think this is more based on weather patterns than anything, especially as the nearshore waters start to warm. I believe they will go inshore and offshore very quickly. I do hope that others chime in, especially those that fish heavily during this time of year including charters for their perspective.

Good luck in your study!
Boatless!

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A Study on Coho Salmon Sep 27, 2019 2:54 pm #25359

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Do you by chance work for or are affiliated with us fish and wild life services?
It's better to ask forgiveness than for permission.

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A Study on Coho Salmon Sep 27, 2019 4:31 pm #25361

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Interesting study good luck. Your best information would probably come from Indiana Lake Manager Ben Dickeson, and Lake Michigan Basin co -ordinator Jay Wesley (Michigan)
Lickety-Split

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but by the moments that take your breath away

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A Study on Coho Salmon Sep 27, 2019 7:53 pm #25362

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I’ve yet to see it here. Most of my spring fish are empty when caught trolling. When I’m fishing real early in the lower section of Trail or the ditch or right in the river mouths, I’ll regularly find small gobies, single eggs, or other fishermen’s bait like pieces of cocktail shrimp, skein, or spawn sacs. This summer I witnessed a new one for me and that was perch with bellies full of spiny water fleas. Of course nobody seems to be interested in studying or restoring perch...

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A Study on Coho Salmon Sep 28, 2019 6:33 am #25363

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I’ve been a Lake Michigan “coho” fisherman since 1979 and a charter captain on Lake Michigan since 1998. I hold a degree in wildlife biology and worked for the Indiana Div. Fish and Wildlife for 38 years. Being old and battle scarred doesn’t make a person an expert, but even a career custodian at MIT probably knows a bit more physics than the average guy on the street.

Lake Michigan cohos have been migrating to the south end of Lake Michigan since 1968 (since they were first stocked in 1966). At the time the lake was swarming with both alewife and Diporea so they didn’t migrate to the south end due to food; rather, to seek out comfortable temperatures.

Also, they don’t move to the southern end in the spring (or late winter). They actually move to the southern basin in late autumn - migrating ever southward as the lake cools from north to south, stopping when they meet rapidly cooling waters from the shore and then, with no other place to go, they overwinter basically in the area just north of where IN, IL and MI come together. I’ve caught them out there - we called them “next year’s coho” - in December, back when I was young, foolish and obsessed.

As the shallows warm nearshore in late February a portion of these fish move from offshore to nearshore areas - almost entirely restricted to Indiana shoreline areas - often concentrated in warm water areas - industrial discharges and stream outflows.

These fish are not yet “fish eaters” for some reason. I’ve caught hundreds if not thousands of them in warm water areas in the late winter and in shallow water areas from the IL line to the Michigan line in early spring (say the first 10 days of April) and I can count the number of minnows or other small fish I've found in their bellies - even in warm water areas where shad, shiners and other small fish are present. If there is anything in the coho at this time of year, it’s tiny unidentifiable black bugs. I truly believe for many of these cohos, the first fish they ever tried to eat in their life was the lure at the end of my line.

When alewives were abundant in the lake (and thus here in Indiana) the cohos came to shore in late winter to warm up, the alewives showed up to spawn in mid-April, the cohos learned to eat alewives and hung around until early May and when the alewives left (and the nearshore waters warmed into the mid-50s) then both the alewives and cohos headed north to cooler waters and to follow the alewife spawn on north.

Not all of the cohos migrate into the Indiana shallows in late winter. A portion simply stayed out in the offshore areas, and ate whatever bugs or shrimp or diporea they could find. Witness the years when the nearshore waters warmed early, there were no baitfish nearshore and the cohos left, often in the second half of April. If you wanted to catch a coho it was necessary to head offshore to the areas where the cohos had wintered and fish for the fish which hadn’t migrated to nearshore areas.

You could easily differentiate between fish from the two “schools.” By the time the nearshore fish deserted the shallows they’d grown from 16-inchers, barely over the one pound mark to three or four pounders. Once they switched to an alewife diet, you could almost see them grow day to day, certainly week to week. Offshore, however, the fish which didn’t migrate to shore didn’t have alewives to eat, didn’t grow rapidly and a two-pounder was a good size.

When the alewife decline was at its worst, the cohos still came to warm up, quickly deserted the Indiana shallows (often by the third week of April) and presumably just rejoined their brethren offshore where, when the offshore waters finally started to warm, the possum shrimp and other zooplankton started to bloom and for lack of anything better to eat (like alewives) that’s what they ate.

Last spring alewife numbers in the south end of the lake in April and May were suddenly back to historic numbers. The cohos didn’t desert our end and in fact, most of them stayed here longer than normal to the detriment of anglers up north of Chicago and into Wisconsin.

I had some customers who fished with me a couple days in late May, caught plenty of cohos the first day, a few more the second day and then wanted to catch some trout. So we pulled lines and headed offshore where there were plenty of lakers and we still caught a few cohos, but the offshore salmon were little two-pounders. Again, I would guess the first fish they tried to eat was my lure.

I don’t know what “ocean” cohos eat, but I surmise there’s a time in their life cycle they make the switch from eating bugs and krill to herring or whatever other bait fish are around. In the Great Lakes they eat bugs and shrimp then switch to alewives. Those offshore cohos gorged on possum shrimp aren’t eating them because they like them or even flourish on them. They are alewife-starved.
The following user(s) said Thank You: Dirty, bob, Pikesmith, Bk, Wildkat Tim, SweetDaddy, Supernaut, StormJunkie

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A Study on Coho Salmon Sep 28, 2019 6:48 am #25364

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Good info Mike.

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A Study on Coho Salmon Sep 28, 2019 9:28 am #25366

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My thoughts exactly. Two different groups of fish and when no alewives were present nearshore a few years ago, fish that would normally start eating alewives moved back into deeper water. Two years in a row there were almost no silver fish caught near shore in the Classic. Pro Tournaments were won by boats fishing deep for offshore Coho/Trout or running to Chicago where nutrients were holding small groups of alewives and Coho nearshore. The fish eating shrimp and bugs in deep water stayed small all year long.

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