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Coho

Coho Salmon Central California Coast ESU
Oncorhynchus kisutch

NMFS Science Center Photo

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Coho Salmon Central California Coast ESU
Oncorhynchus kisutch

Under the Endangered Species Act, discrete populations of a species may be listed even though the species as a whole is not in danger.  These populations are sometimes called evolutionarily significant units, or ESUs.  Such is the case with Coho salmon:  The Central California Coast Coho ESU, which includes all naturally spawned populations from Punta Gorda to the San Lorenzo River (excluding the Sacramento-San Joaquin River system), are the Coho you’ll find in the GGNRA.
Coho salmon (aka silver salmon or salmon trout, among other names) have dark blue or green backs and silver sides that turn a deep red when it is time to spawn.  They are typically about six to 12 pounds these days, and live only about three to four years.  Like most other salmon, they are anadromous (they return from the ocean to their native streams to mate), and semelparous (they spawn only once and then die). 

Spawning occurs from November to January. Big Year Participants Spot Salmon The females use their tails to dig out a series of nests (“redds”) and lay thousands of bright red eggs, which hatch the following spring.  The young salmon spend at least a year in the stream before slowly making their way downstream.  During this time, a miraculous transformation occurs:  Their gills and kidneys adapt from freshwater to saltwater!      

After a year or so at sea, the Coho gather at the mouth of the river, waiting for the rains to come and wash out the sand bars that block their way home to spawn.  It is theorized that salmon find their way by using their sense of smell, which is hundreds of times more acute than a dog’s!  But however they do it, they undergo yet another miraculous transformation in the process:  Their digestive organs disappear, making room in the abdomen for eggs or sperm!  This means that by the time they get upriver, they haven’t eaten for months.

The Central California Coast ESU was declared threatened in 1996, and critical habitat was designated in 1999.  In 2005, the Central California Coast ESU was formally listed as endangered.

Overall 2007-08 was a dismal year for spawning Coho Salmon. Spawning salmon declined by over 80% in most creeks in Western Marin, and a total collapse of the year class in the GGNRA's Redwood Creek: no Coho were observed during the entire 2007-08 survey period. Although the reasons for this decline are not entirely known, one theory focuses on ocean conditions. As the Coho migrated out to the ocean during the spring of 2006 they were faced with the problem of finding food in a nutrient depleted environment. Coho smolts rely on coastal upwelling during the late spring and early summer to bring cool nutrient rich waters up to their hungry mouths. In 2006 this did not occur and the coho smolts were likely faced with famine.

Conservation Action Item

Coho Rescue

Every summer as spawning streams dry, Coho Salmon need to be rescued from desiccating rivers. Work with SPAWN to rescue wild Coho from their desiccated natal streams.

 

 

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Previous Comments

Posted by: Steve Price | 2008-06-04 16:48:14

Saw a fingerling swimming in the pools of Redwood Creek, Muir Woods. This is an easy walk and especially good early in the morning before the tourists arrive.

 

Posted by: Liz | 2008-06-26 17:28:20

It says that the Coho are only endangered on the Central California Coast, but I thought the Coho run in the Lagunitas Creek Watershed (Marin) was endangered also - isn't that part of GGNRA?

 

Posted by: Chris Pincetich | 2008-08-20 16:29:39

Stephanie - YES! Our coho in the Lagunitas Creek watershed in GGNRA are in the Central Cal ESU according to agency biologists. Join us this coming Saturday to see and save them! Read all about SPAWN\'s efforts to relocate them before their habitat dries up at our web site....www.spawnusa.org. See you on the creek, Chris

 

- Stefanie Gandolfi