Coho Salmon

Oncorhynchus kisutch


  • Coho — first stocked in 1933; early introduction attempts not successful
  • Coho and Chinook reintroduced in Michigan, Ohio and Wisconsin waters (1966-1967)
  • Millions of Coho and Chinook now stocked throughout lower Great Lakes
  • Some significant natural reproduction recorded in Great Lakes tributaries
  • Feed mainly on alewives; provide a very important sport fishery in lakes Michigan, Huron and Ontario

Etymology

Oncorhynchus is derived from Greek words for “hooked snout”; kisutch is a vernacular name for the species in Kamchatka; coho is the species name from the Salish language of Pacific Northwest Native Americans.  The coho salmon is more commonly referred to as silver salmon in Alaska.

Life History

In Lake Michigan tributaries, cohos typically spawn on shallow gravel nests (redds) in October and November. Eggs hatch in April, and juvenile cohos (parr) remain in streams for one year before turning silver (smolting) and heading for the big lake. Most coho spend 18 months feeding in Lake Michigan before returning to natal streams, but some precocious males (jacks) spend only six months in the big lake.

Diet

In marine environments, coho salmon feed on a variety of fish species, squid, and even jellyfish. In Lake Michigan, adult coho diet is dominated by small alewife.

Size & Master Angler Entries

The Michigan state record coho weighed 30 pounds, 9 ounces and was caught in 1976. To qualify for a MDNR Michigan Master Angler Award (Catch & Keep), a coho salmon must weigh at least 12 pounds. Lake Michigan supports the bulk of Michigan’s coho salmon fishery, and 94% of Master Angler fish since 1994 have been caught in Lake Michigan. An additional 4.5% were caught in tributaries, bays, or connecting waters of Lake Michigan while only 0.5% came from other Great Lakes drainages.

Management Issues

Coho salmon are more expensive to raise in a hatchery than Chinook salmon because Chinook salmon progress from fertilized egg to smolt in 6 months instead of 18. A single coho smolt costs the state more that $1 to produce, while each Chinook smolt costs approximately $0.15.

Importance to Fishery

Although cohos provide an interesting element of diversity to the big lake fishery and make excellent table fare, most trollers prefer the larger Chinook.

Coho salmon are also little more than an interesting side note to most river anglers who target salmonids, as well. However, cohos are targeted by some anglers in heavily stocked waters such as the Platte River and Grand River.

Two strains of coho have been stocked in the Great Lakes: Hinchenbrooke and Michigan. Artificial spawning of the Hinchenbrooke strain was discontinued in 2007 due to poor rate of return. The Hinchenbrooke strain was historically stocked in Thompson Creek, where a naturally reproducing population developed. The Thompson Creek population crashed due to early mortality syndrome (EMS) linked to low thiamine levels and a diet rich in alewife. Although Michigan strain coho are also susceptible to EMS, reproductive failure was more consistently high in Hinchenbrooke strain cohos according to a study published in 2005.