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Chum Salmon Life History

What's New? Introduction Chum Salmon Tales Respect! Honne Names the Salmon Whatever It Takes Recipe Challenge Life History Timeline for Life History, Growth, and Survival Chum Salmon Ages Embryonic Stages Juvenile Stages Adult Stages Chum Salmon Ecosytems Ocean Climate Effects Identifying Chum Salmon Viewing Chum Salmon Kennedy Creek Clarks Creek Piper's Creek Chum Salmon Colors Puget Sound Chum Salmon Introduction Stock Status Summer Chum Recovery Plan Summer Chum Recovery Planning Update Chum Management Management Chronology Fisheries Data Coastal Chum Salmon Introduction Stock Status Chum Management Fisheries Data Columbia River Chum Salmon Introduction Stock Status Recovery Efforts Fisheries Technical Reports Databases Glossary

Description Ocean phase chum salmon Adult chum salmon (Oncorhynchus keta) and sockeye salmon (Oncorhynchus nerka) are distinguished from other Pacific salmon by a lack of distinct black spots on the back and caudal fin. The 19 or 20 short, stout gill rakers on the first arch of the chum salmon distinguish it from sockeye, which have 28 to 40 long, slender gillrakers. Juvenile chum salmon are distinguished by parr marks of relatively regular height that are smaller than the vertical diameter of the eye, and that are faint or absent below the lateral . When in spawning condition, adult chum salmon have greenish to dusky mottling on the sides, with males exhibiting distinctive reddish-purple vertical barring. Adult chum in Washington range in size from 17 to 38 inches, with an average weight of 9 to 11 pounds (see Identifying Chum Salmon). Male chum salmon with spawning colors Washington chum populations are typically fall-timed fish, that is they return in primarily in October and November and spawn in November and December. In Puget Sound, chum populations have developed three genetically distinct lineages; summer, fall, and winter chum. The summer chum stocks spawn in September and October, and winter chum spawn in January and February. WDFW has concluded that these chum groupings comprise distinct major ancestral lineages, defined as stocks whose shared genetic characteristics suggest a distant common ancestry, and display substantial reproductive isolation from other chum lineages. Genetic differences between summer chum stocks in various streams is the result of long standing reproductive isolation of the individual chum populations. This isolation has been afforded by significantly different migration and escapement timing, and geographic separation from other chum stocks on the spawning grounds. Distribution Native chum salmon were historically present in nearly all coastal Washington streams. The species is still present throughout most of its original distribution, with the exception that only limited numbers of stocks still remain in the Columbia River system. In a 1992 Salmon and Steelhead Stock Inventory (SASSI) State and tribal co-managers identified a total of 72 chum salmon stocks in Washington streams; 55 stocks in Puget Sound and the Strait of Juan de Fuca, 14 stocks in coastal streams, and 3 stocks in the lower Columbia River system (see SASSI). Chum salmon use the estuarine and marine areas of Puget Sound, Hood Canal, the Strait of Juan de Fuca, and coastal Washington for rearing and seaward migration as juveniles. The fish spend two to five years in northeast Pacific Ocean feeding areas prior to migrating southward during the summer months as maturing adults along the coasts of Alaska and British Columbia in returning to their natal streams. Life History Strategy Chum have evolved to limit their freshwater life history by migrating immediately to marine waters upon hatching. This life history strategy, which chum salmon share with pink salmon, reduces the mortality associated with the variable freshwater environment, but makes chum more dependent on estuarine and marine habitats. The chart to the right is a graphic depiction of the life cycle of chum salmon. The cycle begins with chum spawning in Washington streams from late August through February, generally in small to medium sized streams or tributaries to larger river systems. Depending upon temperature regimes in spawning streams, eggs reach the eyed stage after approximately 4-6 weeks of incubation in the redds, and hatching occurs approximately 8 weeks after spawning. Alevins develop in the redds for additional 10-12 weeks before emerging from the gravel as fry. Newly emerged chum fry migrate immediately to marine areas, and range in size from 25- 35 mm. The marine life history is similar to other species of salmon, with the chum juveniles typically spending from 3 to 5 years in the north Pacific before returning to spawn. Like the other salmon species, chum salmon die after spawning. Click on image to enlarge Life history timeline To follow the complete chum salmon life cycle, see the Life History Timeline. This chronology tracks the progeny of 100 chum salmon spawners from egg incubation and fry migration, through their ocean life, and ends with returning adults and spawning. General growth and survival rate information is also included. Freshwater Juvenile Life History Incubation Developing chum salmon incubate as eggs or alevins (sac fry) in the gravel for five or six months after fertilization, a time period determined mainly by stream temperature regimes characteristic of Pacific Northwest streams. Stream flow, dissolved oxygen levels, gravel composition, spawning time, spawning density and genetic characteristics also affect the rate of egg/alevin development, and hence gravel residence time. Reported total gravel residence times for chum ranges from 78 to 183 days across the range of chum salmon distribution, dependent on stream temperature. View drawings of the embryonic stages during incubation Emergence and Downstream Migration Chum fry emergence timing in Washington streams can range from as early as the first week in February (summer chum stocks) to as late as the end of May (winter chum stocks). Fry emerge with darkness, and immediately commence migration downstream to estuarine areas, with total brood year migration from freshwater ending within 30 days for smaller streams and rivers. Emerging chum fry have been shown to become very active with darkness, preferring the swiftest areas of downstream flow and often swimming downstream more rapidly than the current. These behaviors, migration in darkness and rapid downstream movement, are strategies that help to minimize predation on the fry. Estuarine and Marine Life History Estuarine Behavior Upon arrival in the estuary, chum salmon fry inhabit nearshore areas. Chum fry arriving in estuaries are initially widely dispersed, but form loose aggregations oriented to the shoreline within a few days. These aggregations occur in daylight hours only, and tend to break-up after dark, regrouping nearshore at dawn the following morning. Observations In Puget Sound show that chum fry commonly form discrete schools and reside for their first few weeks in the top 15 cm of surface waters and extremely close to the shoreline. Studies in Japan report that chum fry orientated in stratified surface waters (20-100 cm depth) upon arrival in the estuary, and show a very strong preference for the lower salinity water (10 to 14 ppt) found above the freshwater/saltwater interface, perhaps as a seawater acclimation mechanism. This nearshore and surface behavior could also be linked to survival, as small size exposes the youngest fry to heavy predation. Preferences for onshore locations may protect the fry from larger fish and schooling behavior may be adaptations for predator avoidance. View drawings of the juvenile life history stages Juvenile chum maintain a nearshore distribution until they reach a size of 45-50 mm, at which time they move to deeper off-shore areas. Chum fry have a preferred depth of between 1.5-5.0 meters at this time and are thought to be concentrated in the top few meters of the water column both day and night. Juvenile Seaward Migration Chum salmon juveniles entering the estuary are thought to immediately commence migration seaward, migrating at a rate of 7 - 14 km/day. Rapid seaward movement may reflect either "active" migration in response to low food availability or predator avoidance, or "passive" migration, brought on by strong marine water surface flows. Most juvenile chum salmon are thought to migrate to open ocean waters during the spring and summer of their first year, however, in Puget Sound, an unknown percentage remain in the sound through the summer of their second year. Ocean bright chum salmon Ocean Migration After two to four years of rearing in the northeast Pacific Ocean, maturing Puget Sound-origin chum salmon follow a southerly migration path parallel to the coastlines of southeast Alaska and British Columbia. The precise timing of this migration from Gulf of Alaska waters for Washington chum is unknown. Chum salmon begin entering the Strait of Juan de Fuca in mid-July, and the return of various stocks continues through December. The great majority of adult chum salmon return to nearshore waters during October and November. Adult Nearshore Migration Comparison of timing of arrival in marine areas adjacent to stream mouths with timing of spawning for various chum stocks suggests that chum may mill in front of their stream of origin for a week or two before entering freshwater. This behavior is likely related to the amount of time required for the chum to complete maturation and to acclimate to freshwater, but may also affected by available stream flows. View drawings of the adult life history stages Age at Return Washington chum mature primarily at 3 and 4 years of age with low numbers returning at age 5 (there are rare observations of age 2- and 6-year fish). Spawning Chum salmon spawners entering small to medium sized streams typically spawn soon after freshwater entry in the lowest reaches of the streams. This characteristic may reflect an adaptation that increases the survival of the newly emerged fry during their migration to marine waters. The small size of migrating chum fry makes them extremely vulnerable to predation mortality, and the short distances to salt waters and the fry's tendency to migrate during the hours of darkness combine to reduce the impacts of predators. Read about how chum salmon are aged from scale samples and how age information is used in producing runsize forecasts for management In large river systems, adult chum salmon often hold in mainstem areas for a period of weeks prior to moving onto mainstem riffles, side channels, and small to medium tributaries to spawn. Competition for mates on the spawning grounds is intense, assuring that the fittest individuals pass on their traits to future generations. Eggs are deposited in the stream gravel in a number of pockets within a larger nest (redd). After spawning is complete, chum salmon die and their carcasses provide vital nutrients to aquatic and terrestrial ecosystems. Upstream migrating chum salmon. Additional Reading Bakkala, R.G. 1970. Synopsis of biological data on the chum salmon, Oncorhynchus keta (Walbaum) 1792. FAO Fish. Synop. 41, U.S. Fish. Wildl. Serv. Circ. 315, 89 p. Johnson, O.W., W.S. Grant, R.G. Kope, K.Neely, F.W. Waknitz, and R.S. Waples. 1997. Status review of chum salmon from Washington, Oregon, and California. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-32, 280 p. See: http://www.nwfsc.noaa.gov/pubs/tm/tm32/index.html Salo, E.O. 1991. Life history of chum salmon, Oncorhynchus keta. In Groot, C., and L. Margolis (eds.), Pacific salmon life histories, p. 231-309. Univ. B. C. Press, Vancouver, B. C., Canada. Washington Department of Fisheries, Washington Department of Wildlife, and Western Washington Indian Tribes. 1993. 1992 Washington State salmon and steelhead stock inventory. Olympia. 212 p. See SASSI "Blue book"

Timeline for Life History, Growth, and Survival