Returning to freshwater, they change body color from a silver to a brown, green or red depending on the species. The males of some species may change their body shape and develop a hooked snout, humped back, and elongated teeth, which are used to attract a mate and defend spawning territory. Salmon stop feeding once they enter freshwater, but they are able to travel many miles to spawning grounds by using the stored energy from their ocean residence.
All adult salmon die after spawning, and their bodies decay, thus providing nutrients to future generations of salmon. High Mortality Although a single female salmon can lay 1, to 17, eggs, very few of those eggs actually survive from fertilization to maturity.
Spawning Salmon reach sexual maturity at 2 to 8 years old. Chinook: mature after years; spawn July - August in large gravel and deep water with a strong current. Sockeye: mature after years; spawn in August in fine gravel cm in diameter on lake shoals or slack water in rivers. Pink: mature at 2 years; spawn August - September over coarse gravel and sand, in riffles with moderate to fast currents.
Coho: mature at 4 years; spawn late September - December; utilize a wide range of spawning sites and currents, often in the farthest reaches of drainage. Chinook: hatching occurs at 12 weeks Sockeye: hatching occurs after 8 to 20 weeks Chum: hatching occurs after 8 to 16 weeks Pink: hatching occurs after 8 to 16 weeks Coho: hatching occurs after 6 to 7 weeks Alevin A newly hatched salmon is called an alevin.
Fry Salmon fry may go to sea shortly after they hatch or may spend several years in freshwater. Chinook: fry have bar-shaped parr marks which are larger than the spaces between. Sockeye: fry have short, oval parr marks, extending a little below the middle of the body; silver in color, with a tinge of blue in the back. Chum: fry have small, distinct parr marks and slight spots on the body; go to sea almost immediately upon emergence and migrate at night. Pink: fry have no parr marks silvery.
Coho: fry have bar-shaped parr marks; rarely have spots on upper half of dorsal fin. Smolt Many physiological and morphological changes occur in a young salmon to help it make the transition from a freshwater to saltwater existence. Life in the Marine Environment Alaskan salmon can stay at sea for up to 7 years, although this varies by species.
Morrow, James E. The freshwater fishes of Alaska. Alaska Northwest Publishing Company. Anchorage Alaska. It is a vital food source for a diversity of wildlife, including orcas , bears, seals, and large birds of prey. Chinook salmon are also prized by people who harvest salmon both commercially and for sport.
The health of Chinook salmon depends on location—Alaskan stocks are very healthy, while those in the Columbia River are in danger. Protection of Chinook salmon is crucial to maintain healthy Pacific Northwest ecosystems and to provide a delicious food source for years to come. From high mountain streams to broad rivers, to estuaries and the ocean, salmon species are our "canaries in the coalmine," alerting us to the impact of climate change on the health of our entire ecosystem.
Salmon will be impacted by climate change in many ways. Loss of Snowpack: Loss of snowpack and shrinking glaciers mean reduced stream flows in summer and fall. Not only would it would be difficult for returning salmon to reach spawning grounds and for juvenile fish to reach the ocean—lower stream volumes also mean warmer water. Warmer Water: The optimum water temperature range for most salmon is 55 to 64 degrees Fahrenheit Warmer summers are also raising stream temperatures, making salmon more susceptible to predators, parasites, and disease.
Massive fish kills have occurred at or above Forest Fires: Warmer, dryer conditions have resulted in a percent increase in the number of major fires and percent increase in the average area burned since the s.
Intense forest fires can completely burn out root systems, contributing to erosion and siltation of nearby rivers. More Severe Storms and Floods: Increasingly heavy winter floods wash away salmon eggs, even scouring away the gravel spawning beds. Severe floods can wash toxic materials into rivers.
Ocean Acidification: Carbon dioxide is making the oceans more acidic, dissolving the shells of tiny mollusks, an important food source for juvenile North Pacific salmon. Warmer Oceans: Warmer ocean waters and shifting currents are prompting a northward shift in the range of some salmon and other fish populations, such as barracuda and Pacific cod. Sea Level Rise: Sea level rise may inundate low-lying estuaries, a critical habitat for salmon as they make their transition between river and ocean life stages.
Where salmon decline, animals that depend on salmon also suffer. To protect salmon, it's important to restore rivers and estuaries by removing unnecessary and harmful barriers, and to address the root causes of land-use problems. The Species in the Spotlight initiative is a concerted agency-wide effort to spotlight and save…. Learn about the threats facing salmon and what you can do to help.
What habitat features give salmon and steelhead a chance to thrive, and what conditions are…. Chinook Salmon Oncorhynchus tshawytscha. Quick Facts Region. Alaska, West Coast. Population There are numerous stocks of Chinook salmon.
Fishing Rate Managers set fishing rates to avoid jeopardizing the survival and recovery of Chinook salmon stocks that are below their target levels. Habitat Impacts Fishing gear used to catch Chinook salmon rarely contacts the ocean floor and has little impact on habitat. Bycatch Regulations are in place to minimize bycatch. They have black spots on the upper half of the body and on both lobes of the tail fin.
Chinook salmon also have a black pigment along the gum line, thus the nickname "blackmouth. This color change is particularly evident in males. Spawning adult males can be distinguished by their hooked upper jaw. Females can be distinguished by a torpedo-shaped body, robust mid-section, and blunt nose. Juveniles in fresh water fry have well-developed parr marks on their sides the pattern of vertical bars and spots useful for camouflage.
Before juveniles migrate to the sea, they lose their parr marks and gain the dark back and light belly characteristic of fish living in open water. Chinook salmon are anadromous—they hatch in freshwater streams and rivers then migrate out to the saltwater environment of the ocean to feed and grow. They spend a few years feeding in the ocean, then return to their natal streams or rivers to spawn, generally in summer or early fall. Chinook salmon sexually mature between the ages of 2 and 7 but are typically 3 or 4 years old when they return to spawn.
Chinook dig out gravel nests redds on stream bottoms where they lay their eggs. All Chinook salmon die after spawning. Young Chinook salmon feed on terrestrial and aquatic insects, amphipods, and other crustaceans. In the ocean, large boats target this species in very large numbers. While they migrate toward their spawning grounds, Chinook salmon are targeted by smaller-scale operations of fishers — many from native peoples that have relied on Chinook salmon runs for thousands of years.
Unfortunately, overfishing, climate change, and damming of large, coastal rivers all threaten Chinook salmon, and several populations are critically endangered very highly vulnerable to extinction or even extinct.
Dams that prevent this species from reaching its preferred spawning grounds are probably the most detrimental human impact on Chinook salmon populations.
Though they are native only to the north Pacific Ocean, Chinook salmon have been established, purposefully or accidentally, in several other places in the world — including New Zealand, Chile, and other places. Many of the established populations are a result of escapement from aquaculture facilities.
The Chinook salmon is one of the most heavily aquacultured marine species and is the object of a very large market of farmed salmon. Click here or below to download hands-on marine science activities for kids.
0コメント