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This image shows many of the world’s salmon species. U.S. National Marine Fisheries Service
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Salmon is the common name for several species of fish. Salmon can be found in the Pacific and Atlantic Oceans, as well as the Great Lakes. Salmon have quite an amazing life cycle! Typically, salmon are anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce.
What is the life cycle of a salmon?
Life for the salmon begins as an egg in the gravel on the bottom of a stream. This nest, or redd, can contain as many as 5,000 eggs covering up to 30 square feet (2.8 square meters)! The eggs hatch and eventually become fry, with camouflaging vertical stripes. The fry stay for one to three years in their stream before becoming smolts, which are bright silver. The smolt body chemistry changes, allowing them to live in salt water. Then the salmon spend about one to five years in the open ocean where they become mature.
The adult salmon then return to the stream where they were born to spawn. No one really knows how the salmon are able to navigate back to the streams they were born in. All we do know is that their keen sense of smell is involved. Prior to spawning, depending on the species, salmon undergo changes. They may grow a hump, develop canine teeth, develop a kype (a pronounced curvature of the jaws in male salmon). All salmon will change from the silvery blue of a fresh run fish from the sea to a darker color.
How far do salmon travel?
Salmon can make amazing journeys, sometimes moving hundreds of miles upstream against strong currents and rapids to spawn. Chinook and sockeye salmon from central Idaho, for example, travel over 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) from the Pacific Ocean as they return to spawn. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning. Freshwater streams and estuaries provide important habitat for many salmon species.
They feed on terrestrial and aquatic insects, amphipods, and other crustaceans while young, and primarily on other fish when older. Eggs are laid in deeper water with larger gravel, and need cool water and good water flow (to supply oxygen) to the developing embryos. Mortality of salmon in the early life stages is usually high due to natural predation and human-induced changes in habitat, such as siltation, high water temperatures, low oxygen concentration, loss of stream cover, and reductions in river flow. Estuaries and their associated wetlands provide vital nursery areas for the salmon prior to their departure to the open ocean. Wetlands not only help buffer the estuary from silt and pollutants, but also provide important feeding and hiding areas.
How do salmon help the trees of the Pacific Northwest grow?
Salmon and grizzly bears play in important role in bringing nutrients from the ocean to the land. Dying salmon in the streams and rivers provide the nutrients necessary to nourish the next generation of salmon. The bears that eat the salmon help to move the nutrients that salmon consumed in the ocean back onto the land.
For example, an adult can eat up to 3000 lbs of salmon per year. While bears retain the energy from the salmon as fat, much of the nitrogen, phosphorus, and other excess nutrients used by plants are deposited by the bears as they walk through the forest. Spruce trees growing along Alaskan streams with healthy salmon runs get almost 20% of their nitrogen from salmon, and over 80% of that nitrogen passed through a grizzly bear. Moving nutrients from the ocean back to the land is an important part of the relationship between the salmon and the grizzly bear.
What are the different types of salmon?
Chinook salmon (Oncorhynchus tshawytscha) are also called King Salmon in the United States, and Spring Salmon in British Columbia. Chinook are the largest of all Pacific salmon, frequently weighing more than 30 lb (14 kg). Chinook salmon can range as far north as the Mackenzie River and Kugluktuk in the central Canadian arctic.
Chum salmon (Oncorhynchus keta) are also called Dog Salmon in the United States. This species has the widest geographic range of the Pacific species: south to the Sacramento River in California in the eastern Pacific and the island of Kyūshū in the Sea of Japan in the western Pacific; north to the Mackenzie River in Canada in the east and to the Lena River in Siberia in the west.
Coho salmon (Oncorhynchus kisutch) are also known as Silver Salmon. This species is found throughout the coastal waters of Alaska and British Columbia and up most clear-running streams and rivers. It is also now known to occur, albeit infrequently, in the Mackenzie River.
Pink salmon (Oncorhynchus gorbuscha), known as humpies in south east and south west Alaska, are found from northern California and Korea, throughout the northern Pacific, and from the Mackenzie River in Canada to the Lena River in Siberia, usually in shorter coastal streams. It is the smallest of the Pacific species, with an average weight of 3.5 lb (1.6 kg) to 4 lb (1.8 kg).
Sockeye salmon (Oncorhynchus nerka) are also called Red Salmon. This lake-rearing species is found south as far as the Klamath River in California in the eastern Pacific and northern Hokkaidō Island in Japan in the western Pacific and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Although most adult Pacific salmon feed on small fish, shrimp and squid; sockeye feed on plankton that they filter through gill rakers.
Additional Links
http://www.adfg.state.ak.us/pubs/notebook/fish/chinook.php
http://www.adfg.state.ak.us/pubs/notebook/fish/pink.php
http://www.blm.gov/education/00_resources/articles/Columbia_river_basin/posterback.html
http://nrs.wsu.edu/Research/Bear-Center/research/ecological.html
References
This information was gathered from the websites above as well as the following websites.
http://en.wikipedia.org/wiki/Salmon
http://www.adfg.state.ak.us/pubs/notebook/fish/sockeye.php
http://www.adfg.state.ak.us/pubs/notebook/fish/chum.php