COHO SALMON


Oncorhynchus kisutch





BACKGROUND





	Coho salmon have been considered the most important commercially 


caught salmonid in Oregon.  Until recently, they were usually the most 


common salmonid in most coastal streams (ODFW 1992).  Compared to other 


anadromous salmonids in Oregon, coho salmon have a very simple life 


history, with populations primarily on a 3-year life cycle.





DISTRIBUTION





	Oregon lies near the southern boundary of the coho salmon range in 


North America.  This range extends from Point Hope, Alaska to Monterey 


Bay, California.  The Oregon Department of Fish and Wildlife (ODFW) has 


provisionally identified 94 populations of wild coho salmon on the 


Oregon coast.  Wild coho salmon occur in most coastal basins.  





LIFE HISTORY





	Adult coho salmon migrate into fresh water in the fall to spawn.  


Spawning of wild coho salmon usually occurs from mid-November through 


February.  Adult spawning coho salmon are typically 3-years old and they 


are often accompanied by 2-year old precocious males known as jacks.  


Spawning occurs primarily in small tributaries located throughout 


coastal basins.  The parents normally exhibit strong homing to their 


natal stream.  Each female lays about 2,500 eggs.





	The eggs hatch in about 35-50 days, depending upon water 


temperature.  The alevins remain in the gravel 2 or 3 weeks until the 


yolk is absorbed and emerge as fry to feed in the spring. Juvenile coho 


salmon spend 1 summer and 1 winter in fresh water. The following spring, 


about 1-year after emergence, they smolt and migrate downstream to the 


sea.  





	The smolts undergo rapid growth in the ocean, reaching about 15-


20-inches by fall of their first sea year.  Little is known of the ocean 


migrations of coho salmon from Oregon coastal streams, however  based on 


recent research, it appears migrations are mostly limited to coastal 


(near shore) waters.  Migration patterns in the ocean during the fall 


and winter are unknown.  During the second summer in the ocean, a 


substantial percentage of these maturing adults are caught in ocean 


troll and sport fisheries.





HABITAT REQUIREMENTS





	Spawning and rearing of juvenile coho salmon generally take place 


in small low gradient (generally less than 3%) tributary streams.  Coho 


require clean gravel for their eggs.  They prefer cool water 


temperatures  (53-58 F. with 68 F. as maximum) for rearing (Reeves et 


al. 1989).  Fry emerge from February to early June and occupy backwater 


pools and stream margins (Nickelson et al. 1992).  During summer coho 


salmon prefer pools in small streams, but in winter they prefer off-


channel areas, and beaver ponds with ample cover (Nickelson et al. 


1992).  Habitat complexity in the form of large and small woody 


structure is important for rearing coho juveniles.  It is usually 


assumed that coho salmon spend only a short time in the estuary before 


entering the ocean.





HATCHERY 





	Coho salmon are propagated at 9 public hatcheries in Oregon 


coastal basins.  Coho salmon production in all these hatcheries is 


funded by state funds except Cole M. Rivers Hatchery in the Rogue Basin 


which is funded by the U.S. Army Corps of Engineers as mitigation for 


dams.  Releases of coho smolts averaged 5.2 million from 1987-1991.  On 


the Columbia River 13 hatcheries release 29.7 million coho smolts.  


Smolts produced from coastal hatcheries and the Salmon And Trout 


Enhancement Program (STEP) are released into the Nehalem, Trask, 


Nestucca, Salmon, Siletz, Alsea, Siuslaw, Umpqua, Tenmile Lakes, Coos, 


Coquille, and Rogue basins.  However, the STEP projects release hatch-


box fry into a variety of other streams.