Chinook Salmon
Oncorhynchus tshawytscha
Profile / Morphology 2
Chinook salmon are easily the largest of any salmon, with adults often exceeding 40 pounds and 3 feet in length. They are anadromous, which means they migrate from the salty ocean to fresh water rivers and streams to spawn, or lay eggs. They spawn only once and then die (this phenomenon is called semelparity). Adults can migrate up to 3000 miles upstream to spawn! They can be distinguished by the small black spots on the back and on the upper and lower lobes of the caudal fin, and the black gums of the lower jaw. While at sea they are dark greenish to blue-black on top of the head and back, and silvery to white on the lower sides and belly.
Diet 3
They feed on terrestrial and aquatic insects, amphipods, and other crustaceans while young. Adults feed primarily on other fishes.
Average lifespan in the wild 3
9 years
Size / Weight 3
This is the largest species of salmon; they can reach up to 59 inches (1.5 meters) in length and 135 pounds (61 kilograms).
Habitat 3
Juveniles prefer streams that are deeper and larger than those used by other Pacific salmon species. Critical habitat has been designated for the 9 ESA-listed chinook salmon ESUs.
Range 3
Chinook salmon naturally range from Hokkaido Japan across the North Pacific and as far south as the Ventura River in California.
Reproductive / Life span 3
Chinook salmon typically remain at sea for 1 to 8 years (most commonly 2 to 4 years). However, a small proportion of yearling males (called “jack” salmon) mature in freshwater or return to freshwater after 2 or 3 months in salt water. Chinook mature at length of around 36 inches (1 meter) and at a weight of 30 pounds (14 kilograms). However, different populations exhibit considerable variability in size and age of maturation, and at least some portion of this variation is genetically determined. There is a relationship between small size and long distance of migration that may also reflect the earlier river entry and the cessation of feeding for chinook salmon populations that migrate to the upper reaches of long river systems.
There are different seasonal (i.e., spring, summer, fall, or winter) "runs" in the migration of chinook salmon from the ocean to freshwater, even within a single river system. These runs have been identified on the basis of when adult chinook salmon enter freshwater to begin their spawning migration. However, distinct runs also differ in the degree of maturation at the time of river entry, the temperature and flow characteristics of their spawning site, and their actual time of spawning.
Adult female chinook will prepare a redd (or nest) in a stream area with suitable gravel type composition, water depth and velocity. The adult female may deposit eggs in 4 to 5 "nesting pockets" within a single redd. Spawning sites have larger gravel and more water flow through the gravel than the sites used by other Pacific salmon species. After laying eggs in the redd, adults will guard the redd from just a few days to nearly a month before dying.
Chinook salmon eggs will hatch 3 to 5 months after deposition, depending upon water temperatures. Eggs are deposited at a time to ensure that young salmon fry emerge during the following spring when productivity in the river or estuary is sufficient for juvenile survival and growth.
Juveniles may spend from 3 months up to 2 years in freshwater before migrating to estuarine areas as smolts, and then into the ocean to feed and mature. As the time for migration to the sea approaches, juveniles lose their parr marks (the pattern of vertical bars and spots previously useful for camouflage) and gain a dark back and light belly coloration used by fish living in open water. These chinook 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).
Two distinct types or races among chinook salmon have evolved.
One race, described as a "stream-type" chinook, is found most commonly in headwater streams of large river systems. Stream-type chinook salmon reside longer in freshwater, and perform extensive offshore migrations in the central North Pacific before returning to their birth, or natal, streams in the spring or summer months. Stream-type juveniles are much more dependent on freshwater stream ecosystems because of their extended residence in these areas. A stream-type life history may be adapted to areas that are more consistently productive and less susceptible to dramatic changes in water flow. At the time of saltwater entry, stream-type (yearling) smolts are much larger, averaging 3 to 5.25 inches in length (7.6 cm to 13 cm), depending on the river system, than their ocean-type (subyearling) counterparts, and are therefore able to move offshore relatively quickly.
The second race, called the "ocean-type" chinook, is commonly found in coastal streams in North America, particularly populations south of the Columbia River in Oregon. Ocean-type chinook typically migrate to sea within the first three months of life, but they may spend up to a year in freshwater prior to their migration to the sea. They also spend their ocean life in coastal waters. Ocean-type chinook salmon return to their natal streams or rivers as spring, winter, fall, summer, and late-fall runs, but summer and fall runs predominate. They tend to use estuaries and coastal areas for juvenile rearing more extensively than other Pacific salmonids. The evolution of this ocean-type life history strategy may have been a response to the limited carrying capacity of smaller stream systems and unproductive watersheds, or a means of avoiding the impact of seasonal floods. Ocean-type chinook salmon tend to migrate along the coast.
Chinook salmon can live up to 9 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 3
Chinook salmon are very similar to coho salmon in appearance while at sea with their blue-green back with silver flanks. However, their large size, small black spots on both lobes of the tail, and black pigment along the base of the teeth are differentiating factors.
Found in the following Estuarine Reserves 3
Kachemak Bay (AK), Padilla Bay (WA), South Slough (OR), San Francisco (CA), Elkhorn Slough (CA)
Water quality factors needed for survival 3
This is the largest species of salmon; they can reach up to 59 inches (1.5 meters) in length and 135 pounds (61 kilograms).
Water quality factors needed for survival:
•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 3
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.
•Introduction of non-native species which has resulted in increased predator populations
•Hatchery fish interactions; including competition, 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
Conservation notes 3
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 connectivity and complexity in these areas, 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.
Importance to Humans and Estuaries
Chinook salmon are fished commercially and recreationally throughout their range. They can occur in high numbers, and because of their migratory lifestyle, they are a significant source of nutrients for many larger animals and a variety of birds. Hatcheries and aquaculture programs are used for enhancing chinook 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. The 2008 PCSRF report summarizes their work in detail.
Sources and Credits
- (c) Michael Jefferies, some rights reserved (CC BY-NC), http://www.flickr.com/photos/14573979@N00/291282984
- Adapted by GTMResearchReserve from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Oncorhynchus_tshawytscha
- (c) GTMResearchReserve, some rights reserved (CC BY-SA)
