Coho Salmon, Central California Coast ESU
Oncorhynchus kisutch (Fishes)
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 GGNP.
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. 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 2008-09 was a dismal year for spawning Coho Salmon in the GGNP. Spawning salmon in Western Marin had their worst run in four generations. In Redwood Creek, only four individual spawners were seen all year, and only two redds were seen all year. Overall, Redwood Creek had an 83% decline compared to the previous return for this class of Coho.
The 2009-10 year was a bit better than the previous year, but the population numbers are still far below recent spawning runs, causing federal biologists to declare this Coho ESU in an extinction crisis. Some biologists have estimated that the population today is less than 1% of its historic size.
In 2010, Golden Gate National Parks Endangered Species Big Year participants found the first spawning Coho Salmon in Muir Woods, the day after Christmas. The sighting was reported to the National Park Service, which then sent out a survey team and discovered 5 spawning Coho and 2 Coho redds. Although a hopeful sign, the future of the population is uncertain.
Conservation Action Item
Rescue trapped Coho:
Volunteer in Marin to rescue fish from drying streams
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.
Big Year Competitors have reported 0 sightings and taken 0 actions to help this species recover so far this year.
Get Your Spawn On: Searching for Endangered Salmon at Muir Woods
Sunday, 22 Jan 2012, 10:00 - 12:00 Pacific Time (US & Canada)
Steelhead Restoration Day
Sunday, 19 Aug 2012, 09:30 - 12:30 Pacific Time (US & Canada)
Muir Woods Big Year Salmon Stroll
Sunday, 02 Dec 2012, 11:00 - 13:30 Pacific Time (US & Canada)
Win a Patagonia Bag!
Saturday, 01 Dec 2012, 04:00 - 12:00 Pacific Time (US & Canada)
Log in to participate in Big Year!