Coho Salmon Fishing on Lake Michigan

The spring fishery that made the Great Lakes salmon program

Coho were the first Pacific salmon planted in Lake Michigan, going into Michigan tributaries in 1966, and the fish that convinced a skeptical public the whole experiment might work. They are smaller than chinook, they mature in three years instead of four, and they behave completely differently: where a king sits deep and solitary, a coho travels in a school near the surface and eats almost constantly.

That behavior is why the southern-basin spring fishery exists. In April, the shallow water from Michigan City to Waukegan warms faster than anything else in the lake. Plankton blooms, baitfish move in, and coho follow, sometimes by the thousand, into water shallow enough that a 16-foot boat can reach them.

Temperature is the whole game in April

Coho want 48 to 55 degrees. In early spring nothing on the lake is that warm except the near-shore band, river plumes, and power plant discharges. Find the warm water and you have found the fish. A surface temperature gauge is more useful than a fish finder in April.

The other tool is your eyes. Look for the mud line — the visible seam where brown river water pushes out against green lake water. It is often several degrees warmer on the stained side and holds bait tight against the edge. Troll the seam, with your outside boards in the clear and your inside boards in the stain, and let the fish tell you which side they want.

Why the dodger-and-fly rig persists

Peanut flies behind small dodgers look like nothing in particular and catch coho better than baits that look like something. The dodger’s side-to-side sweep at 1.9 mph imparts an erratic dart to a two-inch fly, and a school of coho will follow it in and commit. Fifty years of southern Lake Michigan boats running orange dodgers is not a superstition, it is a very long uncontrolled experiment with a clear result.

Run a lot of lines. Coho fishing is a numbers game and the schools are tight; a spread of ten rods covering 200 feet of width will find them faster than four rods will. Planer boards, not riggers, are the tool for that job in spring.

Following them north

By late May the southern basin has warmed past what coho tolerate and they leave. Through June and July the fish are off Ludington, Manistee and Frankfort, mixed in with the king fleet and riding the top of the thermocline at 30 to 60 feet. They are bigger by then — 6 to 9 pounds — and you catch them incidentally on a king program.

By September, mature coho stage off the tributaries where they were planted, and the Platte River in Benzie County is the historical center of that. Fish staging in Platte Bay in September will take a spoon in 20 feet of water.

How Lake Michigan coho differ from Superior’s

Superior coho are wild fish that stay small — a 4-pounder is a good one — and they are scattered along the North Shore rather than schooled in a basin. Lake Michigan coho are the product of a large stocking program feeding on a comparatively rich forage base in warmer water, and they grow faster and school harder. The Michigan spring fishery has no equivalent anywhere else on the chain.

Cold-water reality check

April water in southern Lake Michigan is 40 to 48 degrees. That is fully capable of killing a person who goes over the side, and spring wind on this lake shifts hard in the afternoon. Wear an inflatable, keep the VHF on channel 16, and go in when it starts to build. Nobody has ever regretted quitting at noon in April.