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Seafood Watch® Wild Pacific Salmon Report October 8, 2010 Chinook Salmon (Oncorhynchus tshawytscha) Chinook salmon, also called king or spring salmon, is the largest of the Pacific salmon species, with adult fish commonly exceeding 30 pounds. Chinook salmon is Alaska’s state fish and represents an important commercial and recreational species throughout the northern Pacific (Delaney 1994). Distribution In North America, the natural range of freshwater habitats for Chinook salmon stretches from the Ventura River in California northward to Kotzebue Sound in Alaska (Figure 1.1) (DFO 2001). Once at sea, Chinook may swim anywhere from the U.S.-Mexico border to the Chukchi Sea off of Alaska. On the Asian side of the Pacific, Chinook occur in freshwater from the Anadyr River area of Siberia (64 degrees north) southward to Hokkaido, Japan. In marine waters, they are found in the Sea of Japan, Bering Sea, and Sea of Okhotsk (Delaney 1994, Froese and Pauly 2004). ESUs In the contiguous U.S., 17 ESUs of Chinook salmon have been identified: • Sacramento River Winter-run • Upper Columbia River Spring-run • Snake River Spring/Summer-run • Snake River Fall-run • Puget Sound • Lower Columbia River • Upper Willamette River • Central Valley Spring-run • California Coastal • Central Valley Fall and Late Fall-run • Upper Klamath-Trinity Rivers • Oregon Coast • Washington Coast • Middle Columbia River Spring-run • Upper Columbia River Summer/Fall-run • Southern Oregon and Northern California Coastal • Deschutes River Summer/Fall-run As of June 2004, two of these 17 ESUs (Sacramento River Winter-run and Upper Columbia River Spring-run) were listed as Endangered Species. In addition, seven of the 17 ESUs were listed as Threatened Species, and one ESU (Central Valley Fall and Late Fall-run) was designated a Species of Concern (NMFS 2004a). In Alaska, Chinook salmon are managed on a regional basis, rather than dividing the species into ESUs. The four overarching regions in Alaska are: Southeast Alaska, Central Region, Westward Region, and Arctic-Yukon-Kuskokwim Region. Chinook salmon are predominantly harvested in 17
Seafood Watch® Wild Pacific Salmon Report October 8, 2010 Southeast Alaska, but significant commercial landings are taken in all four regions. Once in Alaska’s interior, it is unclear where many fish go to spawn. Life History Traits As with most Pacific salmon, Chinook salmon are anadromous. Many Chinook salmon make farreaching freshwater spawning migrations to reach home streams that form the tributaries to larger river systems (Delaney 1994). These spawning habitats can lie relatively close to the coast or over 3,000 kilometers upriver (PFMC 2004a). For example, Yukon River Chinook spawners bound for Yukon Territory, Canada, can travel more than 3,000 river kilometers during a 60-day period. Chinook do not feed during their return freshwater migrations, and their bodies gradually deteriorate as their energy stores are used up over the course of the run and in the production of gametes (Delaney 1994). Adult Chinook typically spend between one and four years in the ocean before returning to spawn. Chinook salmon usually become sexually mature between their second and sixth year, with a maximum reported age of nine years. As a result, they also vary greatly in size, ranging from less than four pounds to well over fifty pounds (Delaney 1994). Most returning Chinook salmon are between three and five years old (PFMC 2004a), though a significant fraction of Chinook salmon mature at age two to three after spending only one winter in the ocean. These precocious fish are commonly referred to as “jacks” and are usually males (Delaney 1994, PFMC 2004a). During spawning, female salmon each typically deposit several thousand eggs in several gravel nests, called redds (Delaney 1994, Myers et al. 1998). Generally, redds are located in stream bottoms with specific characteristics including clear water and gravel of a size that can be manipulated by the fish (PFMC 2004a). In Alaska, eggs usually hatch in late winter or early spring, depending on time of spawning and water temperature (Delaney 1994). The newly hatched fish, called fry, live in the gravel for several weeks, absorbing the food in their attached yolk sacs. These fry then emerge, and, after maturing into smolts capable of living in salt water, migrate downstream towards the ocean, though they may pause in lakes or estuaries before entering the marine environment (PFMC 2004a). In Alaska, most juvenile Chinook salmon remain in fresh water for a year, and migrate to the ocean in their second year of life (Delaney 1994). Once at sea, Chinook salmon can travel widely. The adult fish prey on a wide diversity of organisms, including “fish, squid, euphausiids, amphipods, copepods, pteropods, crustacean larvae, gelatinous zooplankton, polychaetes, chaetognaths, and appendicularia” (Kaeriyama et al. 2004). Despite these commonalities, Chinook salmon also show significant life history variation between fish. Scientists have identified two kinds of Chinook salmon, one called stream-type and the other called ocean-type (Myers et al. 1998). There are significant differences in the age at which they move to the sea, their migration patterns, and spawning times, between the two types of Chinook. Stream-type Chinook spend more time in streams (one to two years) before they head out to the ocean. Once they are in salt water they make long voyages away from their natal streams and come back early before spawning. Adult stream-type Chinook typically enter rivers in the spring and summer, and spawn in late summer or early fal1 (PFMC 2004a). Conversely, ocean-type Chinook spend less time in fresh water (just a few days to months), though they may remain longer in estuarine areas. Once ocean-type Chinook reach the ocean they stay close to their natal streams, but only return to freshwater just before spawning (Delaney 1994, DFO 18
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