Coho Salmon
Oncorhynchus kisutchProfile / Morphology 1
Coho salmon are anadromous, migrating from the ocean to spawn in fresh water. They spawn only once and then die (called semelparity). Coho salmon have dark metallic blue or greenish backs with silver sides and a light belly and there are small black spots on the back and upper lobe of the tail while in the ocean. Spawning males develop a strongly hooked snout and large teeth. Adults migrate up to hundreds, even thousands, of miles upstream to spawn!
Diet 2
In their freshwater juvenile stages, coho feed on plankton and insects, and switch to a diet of small fishes as adults in the ocean.
Average lifespan in the wild 2
5 years
Size / Weight 2
2 feet (.6 meter) maximum / 36 lbs (16 kg) maximum
The size of an adult coho may measure more than 2 feet in length and they can weigh up to 36 pounds. However, the average weight of adult coho is 8 pounds.
Habitat 2
Coho spend approximately the first half of their life cycle rearing and feeding in streams and small freshwater tributaries. Spawning habitat is small streams with stable gravel substrates. The remainder of the life cycle is spent foraging in estuarine and marine waters of the Pacific Ocean. Critical habitat was designated on May 5, 1999 for the Central California Coast and Southern Oregon/ Northern California Coast coho salmon.
Tolerance
Because coho salmon do not spend a large part of their life in estuaries, and migrate between the sea and freshwater, they are euryhaline. They are only moderately tolerant of other stressors.
Range 2
Coho salmon naturally range from Hokkaido Japan across the North Pacific and as far south as Central California.
Reproductive / Life span 2
Adults return to their stream of origin to spawn and die, usually at around three years old. Some precocious males known as "jacks" return as two-year-old spawners. Adults typically begin their freshwater spawning migration in the fall and spawn by mid winter. Females prepare several redds (nests) in a stream area with suitable gravel type composition, water depth and velocity. The eggs will remain in these redds for six to seven weeks until they hatch. After laying eggs in the redd, adults will guard the redd from just a few days to nearly a month before dying. Juveniles rear in fresh water for up to15 months, and then migrate to the ocean in the spring. As the time for migration to the sea approaches, juveniles lose their parr marks, the pattern of vertical bars and spots useful for camouflage. They then gain the dark back and light belly coloration used by fish living in open water. These coho salmon “smolts” seek deeper water, avoid light, and their gills and kidneys begin to change so that they can process salt water (the whole process is called smoltification). Coho salmon typically spend two growing (summer) seasons in the ocean before returning to their natal streams to spawn as three year-old adults.
Coho salmon can live up to five years. Jacks take an alternative mating strategy and re-enter streams when small and young. They sneak in and spawn just at the time a large dominant male has courted and convinced a female to mate with him
Relatives 2
Coho salmon are very similar to chinook salmon in appearance while at sea (blue-green back with silver flanks), except for their smaller size, lack of small black spots on both lobes of the tail, and lighter pigment along the gumline at the base of the teeth. Spawning fish found in inland rivers are dark with reddish-maroon coloration on the sides.
Found in the following Estuarine Reserves 2
Kachemak Bay (AK), Padilla Bay (WA), South Slough (OR), San Francisco (CA), Elkhorn Slough (CA)
Water quality factors for survival 2
•Water Temperature: 0 to 25°C
•Turbidity: low to moderate
•Water Flow: low to high
•Salinity: 0 to 35 ppt
•Dissolved Oxygen: moderate to high
Threats 2
Salmonid species on the west coast of the United States have experienced dramatic declines in abundance during the past several decades as a result of human-induced and natural factors. There is no single factor solely responsible for this decline. Given the complexity of salmon life history and the ecosystem in which they reside, it is difficult to precisely quantify the relative contribution of any one factor to the decline of the species.
Some of the threats facing the Chinook salmon include:
•Dams, water development projects, and other impediments have reduced or eliminated fish habitat and increased mortality rates. Modified natural water flow regimes have also resulted in increased
•water temperatures, changes in fish community structures, and depleted flows necessary for migration, spawning, and rearing.
•ntroduction of non-native species which has resulted in increased predator populations
•Hatchery fish interactions; including ccompetition, genetic introgression, and disease transmission
•Habitat loss due to natural resource and land use activities, such as logging, road construction, urban development, mining, agriculture, and recreation
•Changing environmental conditions, such as droughts, floods, and climate change Pollution
The degree of which water can move and flow freely between and within watersheds is an important consideration for maintaining healthy aquatic riparian ecosystems. Loss of this connectivity and complexity, such as the loss of deep pool habitats, has contributed to the decline of salmon. Studies indicate that in most western states, about 80 to 90 percent of the historic riparian habitat has been eliminated. Further, it has been estimated that during the last 200 years, the lower 48 United States have lost approximately 53 percent of all wetlands.
Salmon have been, and continue to be, an important species for recreational fisheries throughout their range. Commercial fishing on unlisted, healthier stocks has caused adverse impacts to weaker stocks of salmon, and illegal high seas driftnet fishing in past years may have also been partially responsible for declines in salmon abundance. However, such fisheries cannot account for the total declines in salmon in North America.
In an attempt to mitigate for lost habitat and reduced fisheries, extensive hatchery programs have been implemented throughout the range of salmon on the west coast. While some of these programs have been successful in providing fishing opportunities, the impacts of these programs on wilds stocks are not well understood. Competition, genetic introgression, and disease transmission resulting from hatchery introductions may significantly impact the production and survival of wild salmon. Commercial and recreational fisheries targeting stronger stocks supported by hatchery production may inadvertently result in adverse impacts to weaker, wild stocks. Furthermore, collection and utilization of wild fish for breeding purposes may result in additional negative impacts to small or dwindling natural populations.
In recent years, some populations have shown encouraging increases in population size. Population trends for specific ESUs can be found in the 2005 status review report for Pacific salmon and steelhead.
Conservation notes 2
Importance to Humans and Estuaries
Coho salmon are fished commercially and recreationally throughout their range. In many areas they occurred in high numbers, and because of their migratory lifestyle, they were a significant source of nutrients being brought into and out of estuaries where they served as prey for many larger animals and a variety of birds. Hatcheries and aquaculture programs are used for enhancing coho as a food source and in restoration programs. Salmon have particular cultural significance to many native peoples from throughout their range.
How to Help Protect This Species
Chinook salmon use estuaries and freshwater areas. They are susceptible to water pollution and damage to and alteration of stream channels and riparian zones. Therefore, efforts to protect the species include:
•Minimize runoff of neighborhood pollutants, fertilizer, and sediment into local streams are helpful to this species, and other estuary dwelling species.
•Join a stream or watershed advocacy group in your area to protect your local estuary ecosystems.
•Advocate the implementation of effective fish passage solutions so fish can bypass dams and artificial barriers.
•Support restoration of more natural water flow regimes.
•Support research into the ecology and conservation of the species
Current conservation efforts typically include: captive-rearing in hatcheries, removal and modification of dams that obstruct salmon migration, restoration of degraded habitat, acquisition of key habitat, and improved water quality and instream flow. The Pacific Coast Salmon Recovery Fund (PCSRF) was established by Congress in 2000 to support the restoration of salmon species. The fund is overseen by NMFS and carried out by state and tribal governments.
Sources and Credits
- Adapted by GTMResearchReserve from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Oncorhynchus_kisutch
- (c) GTMResearchReserve, some rights reserved (CC BY-SA)
