Coho Salmon: How to Tell a Silver From a King, Size, Runs and Records

The coho salmon (Oncorhynchus kisutch), the silver salmon of Alaska and the Pacific Northwest, is a 24 to 30 in (61–76 cm), 8 to 12 lb (3.6–5.4 kg) fish that spends half its three-year life in a small stream and the other half at sea. It is also the fish that started the Great Lakes salmon fishery in 1966. Below: how to tell a coho from a king in the net, how big they get, when they run from Alaska to Lake Ontario, how the agencies say to catch one, and where the record fish came from.

The world-record coho did not come from the Pacific. Jerry Lifton’s 33 lb 4 oz fish was caught in the Salmon River at Pulaski, New York, in 1989, and New York’s own state record, from Lake Ontario, is three ounces heavier.

Coho or chinook: check the gum line

Every agency lands on the same two marks. A coho has a white gum line at the base of its lower teeth, and spots only on the upper half of its tail. A chinook has a black gum line and spots on both halves. Oregon’s fish and wildlife department adds that enforcement officers go by the lower jaw, and that size settles nothing.

The marks come from the identification cards of Alaska, Washington and Oregon, Michigan DNR and the Great Lakes Sea Grant guide. Ignore the color of the rest of the mouth: Alaska’s chart calls a coho’s mouth black and Washington’s card calls it light. The gum line is the part they all agree on.

Fresh from the ocean or the lake a coho is bright silver, which is where “silvers” comes from. On the spawning run both sexes turn dark maroon with a dark back, and the male grows a hooked snout.

How big do coho salmon get?

Alaska’s figure is the standard one: 24 to 30 in and 8 to 12 lb. Washington says 6 to 12 lb, and Oregon notes they rarely pass 15 lb (6.8 kg). The U.S. Fish and Wildlife Service gives the extreme as 42.5 in (108 cm) and 36 lb (16.3 kg).

Great Lakes coho are smaller on average. Michigan DNR puts the typical adult at 5 lb (2.3 kg); Wisconsin’s range for Lake Michigan is 5 to 12 lb. Lake Ontario is the exception, and its fish hold the top of the record book.

A three-year life

A coho hatches in stream gravel, spends about its first year and a half in fresh water, and then goes to sea, or out into the lake, for another year and a half. It comes back in its third fall, spawns once and dies. Some males return a year early at about 12 in (30 cm); those are the jacks.

Young coho need slow water and sunken wood: ponds, side pools and log jams out of the current. Adults favor small water too. Washington finds them in nearly every small coastal stream with a year-round flow, waiting at the mouth until rain lifts the level. A coho can clear more than 6 ft (1.8 m) in one leap.

A female lays 2,400 to 4,500 eggs in a gravel nest called a redd. Spawning water runs 40 to 49 °F (4–9 °C).

Where coho live, and how they got to the Great Lakes

The native range circles the North Pacific: from Japan and eastern Russia across the Bering Sea, through Alaska, and down the coast to Monterey Bay in California.

The Great Lakes fish are immigrants with a known birthday. In fall 1964 the Oregon Fish Commission shipped Columbia River coho eggs to a Michigan hatchery. Howard Tanner, the state’s fisheries chief, wanted a predator for the alewives that were washing up dead on Lake Michigan’s beaches. On April 2, 1966, the first smolts went into the Platte River from a golden bucket. By 1970 anglers took 576,000 coho from Lake Michigan in a single year. Tanner died in August 2026, aged 102.

Coho now swim in all five Great Lakes, and nearly all of them are stocked: Michigan plants most of its fish in the Platte River, and New York stocks about 250,000 a year into Lake Ontario. In 2024 coho was the most-caught fish in Wisconsin’s share of Lake Michigan, 210,891 out of 743,492 fish of all species.

When coho run

Lake Michigan’s coho follow the warmth. Indiana DNR describes nearly the whole population gathering in the southern end of the lake in spring, then spreading north along both shores from mid-April. In summer they roam offshore in water below 60 °F (16 °C). Their preferred range is 52 to 58 °F (11–14 °C), the same as a chinook’s; the temperature chart sets that beside 24 other species.

How to catch coho

Coho bite. Oregon’s agency puts it bluntly: colors catch anglers, not fish, and a coho will take almost any color of lure. Alaska calls them the most acrobatic of the Pacific salmon.

1. Troll high. On Lake Michigan, Indiana DNR says to fish the top 15 ft (4.6 m) even over deep water. Oregon gives the same 15 ft for the ocean, at 3 to 5 mph, with a spoon or plastic squid behind a dodger.
2. Run a dodger and fly. Once the lake passes 40 °F (4 °C), Indiana’s pick is an orange 6 in dodger with a small “peanut” fly 14 to 18 in (36–46 cm) behind it, trolled at 1.8 to 2.5 mph. Wisconsin DNR credits trolling with about 90% of the coho anglers keep.
3. From a pier or beach, use bait. Most shore coho in Indiana fall to spawn sacs, skein or a nightcrawler 4 to 6 ft (1.2–1.8 m) under a bobber on 6 to 10 lb line. Half-ounce spoons and spinners take the rest.
4. In rivers, swing a spinner slowly. Oregon suggests a No. 3 in clear water and a No. 5 when it is murky. Terry Wiest of Salmon Trout Steelheader wants the blade turning as slowly as it can and still turn, in deep holes near wood.
5. Or twitch a jig. Cast a ⅜ to ½ oz (11–14 g) jig into slow, deep water, let it sink and lift it with short snaps of the rod. Jason Brooks, in the same magazine, notes that coho take it on the drop.

A coho in a river has stopped feeding. New York’s biologists say river fish strike out of aggression, which is why a lure that annoys them works.

The records

The New York fish outweighs the world record because it was never entered with the IGFA. Michigan’s record came from the Platte, the river that received the first bucket of smolts ten years earlier. Alaska’s stood for 35 years until 2011, when the angler’s party chartered a plane to get the fish to a certified scale in Juneau.

Protected runs, and the tire chemical

On the Pacific coast four coho populations are listed under the Endangered Species Act: Central California Coast coho as endangered, and the Southern Oregon and Northern California, Lower Columbia River and Oregon Coast populations as threatened. California closed its coho fisheries in the early 1990s, so a coho caught there goes back. In Washington and Oregon nearly all hatchery coho have the small adipose fin clipped, and where a fishery is mark-selective only a clipped fish may be kept. Read the rules for the river before you fish it.

Coho are also unusually easy to poison. In Seattle’s Longfellow Creek, 60 to 100% of the adults returning between 2002 and 2009 died before they could spawn, within hours of falling ill. In 2021 a team writing in Science traced the deaths to 6PPD-quinone, a breakdown product of a chemical used in almost every car tire. About one millionth of a gram in a liter of water kills an adult coho.

Are coho good to eat?

Yes. NOAA describes the flesh as mild, more delicate in smaller fish, and a good source of omega-3 fats. Great Lakes coho carry advisories for PCBs that differ by lake, so check your state’s current guide. Wisconsin DNR’s trimming advice applies anywhere: remove the skin, the strip of fat along the back, the belly flap and the dark flesh along the lateral line.

Related

• Types of salmon: the five Pacific salmon and the Atlantic salmon told apart.
• Steelhead: the sea-run rainbow trout that shares the coho’s rivers.
• Fish species: every species guide in one place.