Chinook Salmon are found natively in the Pacific from Monterey Bay, California to the Chukchi Sea, Alaska in North America and from the Anadyr River, Siberia to Hokkaido, Japan in Asia. It has also been introduced to many places around the world including the Great Lakes and New Zealand. (Delehay and ADFG, 1994; Matthews and Waples, 1991; NOAA, 2002; Pacific States Marine Fisheries Commision, 1996; University of Wisconsin Sea Grant Institute, 2002)
The Chinook Salmon is anadromous– born in freshwater, migrating to the ocean, and returning as mature adults to their natal streams to spawn. Freshwater streams, estuaries, and the open ocean are all important habitats. The freshwater streams are relatively deep with course gravel. The water must be cool, under 14 C for maximum survival, and fast flowing. Estuaries provide a transition zone between the freshwater and saltwater and the more vegetation the better because there will be more feeding and hiding opportunities. At sea, Chinook Salmon can either stay close to shore or migrate thousands of miles to deep in the Pacific. (National Wildlife Federation, 1996-2002; NOAA, 2002; Pacific States Marine Fisheries Commision, 1996)
The Chinook Salmon is the largest of all Pacific salmon species, often larger than 100 lbs and longer than 5 ft. It is characterized by a deep blue-green back, silvery sides and a white belly with black irregular spots on the back, dorsal fin and both lobes of the tail. It also has a small eye, black gum coloration, a thick caudal peduncle and 13-19 anal rays. For spawning, both males and females develop a reddish hue on the sides, although males may be deeper in color. Males can also be distinguished by a hooked nose and a ridged back. The Chinook fry look very different, with well developed parr marks (vertical bars) on their sides. (Delehay and ADFG, 1994; Government of Canada, 2002; National Wildlife Federation, 1996-2002; NOAA, 2001; Pacific States Marine Fisheries Commision, 1996)
The female digs a nest (called a redd) in the gravel and then deposits her eggs and the male deposits sperm. After 90-150 days (depending on temperature) the eggs hatch, and the alevins (fry with yolksacs attached to the underside) stay in the gravel until the yolksac is used up. The fry then emerge from the gravel in the spring and feed and grow for a few months to two years, depending on the stream system. They then migrate downstream as smolts, following the natural current. The smolts undergo huge physiological changes in their transition from freshwater to salt water. They then spend the next 1-7 years growing and maturing at sea. Growth rates in the ocean are much faster, and perhaps as much as 99% of the somatic growth occurs as sea. Mature adults will then return to their natal streams to spawn. Once the adults have re-entered freshwater, they no longer feed, and they complete sexual maturation during the freshwater migration (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; NOAA, 2001; Delaney and ADFG, 1994; University of California at Berkeley; Government of Canada, 2002; Ewing and Ewing, 2002; Satterfield and Finney, 2002).
The Chinook Salmon have seasonal runs in which all adults return to their natal streams and spawn at approximately the same time of year. Sexual maturity can be anywhere from 2-7 years, so within any given run, size will vary considerably. Salmon are semalparous, and shortly after spawning they die.
After migrating back to the exact place of birth, with very little straying, the adults span in the course gravel of the river. The female first digs a redd in the gravel with an undulating motion of her tail, while the male stands guard. The female then deposits her eggs (3000-14000) in the nest, sometimes in 4-5 different packets within a single redd. The male then deposits his sperm, and both parents guard the redd until they die, sometime within the next 25 days. Spawning is timed so that the fry will emerge in the spring, the time where the stream has the highest productivity.
Many streams have more than one run, with each run going to a slightly different location in the stream. In each location, different environmental factors will affect the timing of the run, all timed so the fry emerge in the spring. For example, in a stream with spring and summer runs, often the spring run will go to higher elevation and with the colder temperature, the eggs will take longer to hatch (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; Matthews and Waples, 1991; NOAA, 2001; Delaney and ADFG, 1994; Government of Canada, 2002).
There is no parental care in Chinook Salmon, as both parents die before the young emerge. However, the decomposing adult carcasses provide necessary nutrients to the eggs and fry.
The average age of spawning adults is 4-6 years, however, they can spend up to 8 years in the ocean or return after less than one year. The average age is slightly younger in the south with 2/3/4 year-olds most common; 5/6/7 year-olds are most common in the north. Often, females are older than males at sexual maturity. There is high mortality early because of high natural predation, and those smolts that do not reach a certain size before their first winter at sea will not survive colder temperatures. Human modification of the environment has led to even higher mortality, mainly due to siltation and decreased water flow which have reduced the availability of oxygen to the eggs and fry (Pacific States Marine Fisheries Commission, 1996; Delaney and ADFG, 1994; Government of Canada, 2002).
Chinook Salmon are anadromous, making great migrations out to the deepest parts of the ocean and returning as mature adults to their natal streams. In order to return to the exact right stream, they use sun-compass orientation out in the open ocean and then smell to get them to the right stream. All adults return at the same time, spawn so that all fry will emerge at the same time, and then all smolts migrate downstream at the same time.
There are two basic behavior types, stream-type and ocean-type, which depend on the amount of time juveniles spend in freshwater. The stream-types spend 1-2 years in the stream, and are therefore much more dependant on the stream ecosystem than are the ocean-types, which migrate to the ocean in less than 3 months. Stream-types are mostly found in the north, and have chosen more stable streams with consistently high productivity and relatively little change in water flow. Stream-types also usually migrate very far into the ocean whereas ocean-types generally stay close to the coast, migrating north instead. The ocean-types developed in areas with lower carrying capacities or high seasonal flooding. Stream-types deposit a significantly lower number of eggs, and typically these eggs are smaller because their long freshwater migration takes so much energy while they are not feeding, so they have little left to invest in their gametes (Pacific States Marine Fisheries Commission, 1996; Matthews and Waples, 1991; NOAA, 2001; University of Wisconsin Sea Grant Institute, 2002; Healey, 2001).
External fertilization in Chinook Salmon requires precise communication in order to ensure proper timing of gamete release. During the courtship, which can last up to several hours, the male vibrates and crosses in front of the female, while the female is preparing for spawning by digging the redd. The female has been shown to selectively choose larger males, who vibrate more. A few seconds before depositing her eggs, the female will shake quickly next to the male, inducing sperm release (Berejikian, Tezak, and LaRae, 2001).
While in freshwater, Chinook Salmon fry and smolts feed on plankton and then terrestrial and aquatic insects, amphipods and crustaceans. After migrating to the ocean, the maturing adults feed on large zooplakton, herring, pilchard, sandlance and other fishes, squid, and crustaceans. Once the adult salmon have re-entered freshwater, they do not feed. In the Great Lakes, Chinook Salmon were introduced to control the invasive alewife population (National Wildlife Federation, 2002; Delaney and ADFG, 1994; Government of Canada, 2002).
For young Chinook Salmon, predation is very high. Many species eat the fry and smolts, including striped bass, American shad, sculpins and sea gulls. Reaching adulthood does not release them from predation, however, as they are still prey to many animals when they return to spawn. Most common are bears, orcas, sea lions, seals, otters, eagles, terns and cormorants. People have made predation worse by concentrating adult salmon at dams and weirs (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; NOAA, 2001; University of California at Berkeley).
Spawning Chinook Salmon are the keystone species in many streams because so many other species rely on them for food. In the ocean, they are often one of the top predators. Chinook Salmon are now the top predator in the Great Lakes where they were introduced to control other non-native fish species (University of Wisconsin Sea Grant Institute, 2002).
The Chinook Salmon is very important to commercial, recreational, and subsistence fishermen. It has always been central to the Native American lifestyle on the Pacific coast, and now much of the economy of the Pacific Northwest is based on it. Despite being relatively rare (compared to other Pacific Salmon species) it is the most commercially valuable. It is also now an important big game fish in the Great Lakes and is a big tourist draw in both the Pacific and Great Lakes regions
(Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; Delaney and ADFG, 1994; University of Wisconsin Sea Grant Institute, 2002).
The Chinook Salmon has 17 distinct Evolutionarily Significant Units, (ESU) in the US only, two of which are endangered and seven of which are threatened.
Sacramento River Winter Run,
Upper Columbia River Spring Run
Snake River Fall Run,
Snake River Spring/Summer Run,
Central Valley Spring Run,
Central Valley Fall Run
S. Oregon/N. California Coastal,
Upper Klamath Trinity,
Mid Columbia Spring Run,
Upper Columbia Summer/Fall Run,
Deschules Summer/Fall Run
Many agencies have been set up to protect this species, including the Pacific Fisheries Management Council, the North Pacific Fisheries Management Council, and the National Marine Fisheries Service. The federal Magnuson-Stevens Act was made to protect the Essential Fish Habitat, the waters and substrates necessary to fish for spawning, breeding, feeding and growing to maturity. The Sustainable Fisheries Act has amended the Magnuson-Stevens Act.
The main causes for the declining fish populations are overfishing, damming and diverting water, habitat destruction, and introducing hatchery populations. Overfishing has decreased population sizes enough that all other causes, along with natural predation, can have extreme effects, and population sizes decrease rapidly. Damming causes decline because it blocks adults from returning to their birthplace and because smolts often get sucked into the turbines of hydroelectric dams and are killed. Diverting water away from salmon streams causes water temperature to rise, reducing the oxygen carrying capacity of the water. Temperatures could also become fatally high in the summer. Reduced water levels could expose eggs in the winter, or flows could be too low to carry smolts out to sea. Habitat destruction, including logging, clearing rivers, pollution, and wetlands destruction, take away shade and necessary protection for juveniles. After logging has changed runoff patterns, streams may contain too much silt and become uninhabitable. Pollution can cause many physiological problems, including increased susceptibiity to pathogens. Introducing hatchery populations adds to the decline because the introduced populations interbreed with the native populations and can reduce resistence to disease (Pacific States Marine Fisheries Commission, 1996; National Wildlife Federation, 2002; NOAA, 2001; University of Wisconsin Sea Grant Institute, 2002; Arkoosh and Collier, 2002).
Chinook Salmon population sizes have been shown to fluctuate with long-term climate changes. The most dramatic example of this is the El Nino events, every 3-7 years, which bring warm water into the Pacific and negatively affect Chinook Salmon populations. Longer term changes have involved changes in water currents over time, which have had opposite effects in Alaska and along the coast of California. In Alaska, these changes have caused a change in the mixing layer which has increased the chlorophyll levels in plankton, making the system more productive. This has increased the zooplankton population, which in turn causes an increase in the salmon population size. In California, however, climatic changes have caused the mixing layer to deepen, which has reduced the amount of nutrients available, causing the salmon population to decrease (Taylor and Southards, 1997; Satterfield and Finney, 2002; Botsford and Lawrence, 2002; Dalton, 2001).
William Fink (editor), University of Michigan-Ann Arbor.
Caren Scott (author), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
an animal that mainly eats plankton
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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Berejikian, B., E. Tezak, A. LaRae. 2000. Female mate choice and spawning behaviour of Chinook Salmon under experimental conditions. Journal of Fish Biology, 57: 647-661.
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Government of Canada, 2002. "Salmon Biology--Pacific Region" (On-line). Accessed October 23, 2002 at http://www.pac.dfo-mpo.gc.ca/ops/fm/Salmon/chinook.htm.
Healey, M. 2001. Patterns of gametic investment by female stream type and ocean type Chinook Salmon. Journal of Fish Biology, 58: 1545-1556.
Matthews, G., R. Waples. 1991. Status Review for Snake River Spring and Summer Chinook Salmon. NOAA Technical Memorandums.
NOAA, 2001. "Chinook Salmon (Oncorhyncus tshawytscha)" (On-line). Accessed October 21, 2002 at http://www.nmfs.noaa.gov/prot_res/species/fish/Chinook_salmon.html.
NOAA, 2002. "Where do salmon go in the ocean?" (On-line). Accessed October 23, 2002 at http://www.nefsc.noaa.gov/faq/fishfaq2d.html.
National Wildlife Federation, 1996-2002. "Chinook Salmon" (On-line). Accessed October 21, 2002 at http://www.nwf.org/keepthewildalive/salmon.
Pacific States Marine Fisheries Commision, 1996. "Chinook Salmon" (On-line). Accessed October 21, 2002 at http://www.psmfc.org/habitat/edu_chinook_facts.html.
Satterfield, F., B. Finney. 2002. Isotope analysis of Pacific Salmon: insight into trophic status and oceanographic conditions over the last 30 years. Progress in Oceanography, 53: 231-246.
Taylor, G., C. Southards. 1997. Longterm climate trends and salmon population. Oregon Climate Service.
US Food and Drug Administration, 2002. "Regulatory Fish Encyclopedia--Chinook Salmon" (On-line). Accessed October 23, 2002 at http://vm.cfsan.fda.gov/~frf/rfe0kg.html.
University of Calfornia Berkeley, "Chinook Salmon--Onchorynchus tshawtscha" (On-line). Accessed October 21, 2002 at http://elib.cs.berkeley.edu/kopec/tr9/html/sp-chinook-salmon.html.
University of Wisconsin Sea Grant Institute, 2002. "Chinook Salmon" (On-line). Accessed October 21, 2002 at http://www.seagrant.wisc.edu/greatlakesfish/fchinooksalmon1.html.