Oncorhynchus keta

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General Information
Common Name: 
Chum salmon
FID: 
SOK03
Status: 

Conservation Status in California: Class 1, Endangered (Moyle et al. 2011).
While never very common in California, presumed self-sustaining chum salmon populations are small and face extirpation from the state in the near future.

Life History: 

Life History: Because of their economic importance, their life history, wide distribution, and habitat requirements chum salmon have been well studied but mainly in Asia, Alaska, and Canada (Salo 1991, Moyle 2002).
Although chum salmon have been recorded as migrating over 2,500 km up the Yukon River, Alaska, and the Amur River, Russia, they are not particularly strong swimmers for salmon and are easily stopped by low barriers. This results in most chum salmon spawning within 200 km of the ocean. Some populations even spawn in the intertidal reaches of streams. Chum salmon in the northern half of their range in North America tend to spawn in June through September, while more southern populations spawn in August- January. Adults are usually observed in California streams in December and January, but can occur as early as August. In Mill Creek, a tributary to the Smith River, chums enter during mid-December, but only in years when stream flows are high. During years of low flow, the fish may be spawning instead in the mainstem Smith or in larger tributaries.
Adults home to natal streams where they spawn at 2-7 years of age, but primarily at ages 3-5 (Salo 1991, Moyle 2002). Each females digs a connected series of redds in which the eggs are deposited during spawning; the female guards the last redd until she dies. Males are sexually active for 10-14 days, spawning with multiple females. Large females produce over 4,000 eggs, but the average fecundity is 2,400-3,100 eggs. Fertilized eggs hatch after about 2-6 months of incubation, usually from December to February. Alevins absorb their yolk sac in 30-50 days, growing to approximately 35 mm TL before emerging from the gravel. Like pink salmon, fry spend only a short time in fresh water, moving into estuaries soon after emerging from the gravel. Depending on distance traveled, fry in fresh water are 35-70 mm TL. They may remain in estuaries, however, for several months before moving out into more oceanic waters. Movement of fry is mainly nocturnal, unless water clarity is low.
Fry may not feed in fresh water if their downstream migration is short; otherwise they feed on small aquatic invertebrates, primarily as drift. In estuaries, they feed mostly on benthic prey, such as copepods and amphipods. As they move into deeper water and grow larger, chums devour a wide variety of invertebrates as well as fishes. However, for subadults, gelatinous zooplankton, especially pteropods, seem to be especially important in their diet (Salo 1991).

Dispersal Capability: Anadromous.

Habitat Requirements: 

Habitat Requirements: Chum salmon adults and maturing juveniles live in the open waters of the ocean, but juveniles are bottom oriented in rivers and streams. Optimal temperature ranges for freshwater portions of the life cycle are: adult migration, 7-11°C (range, 0-21°C); spawning, 7-13°C; incubation, 4-12°C; fry rearing/outmigration, 11-15°C, although fish can successfully live through periods of suboptimal temperatures (Moyle 2002, Richter and Kolmes 2005). Spawning takes place in gravel 1-10 cm in diameter but optimal gravel size seems to be 2-4 cm (Salo 1991). Relatively shallow depths (13-50 cm) for spawning are preferred.
Eggs and alevins occur primarily in fresh water, although spawning in intertidal areas occurs. The fry prefer shallow ( Environmental tolerances have not been studied for California populations, but limiting factors are likely to be (1) temperatures >13°C for spawning and incubation, (2) intragravel dissolved oxygen in spawning areas at less than 90% saturation, (3) current velocities over spawning areas flowing at less than 30 cm/sec, (4) potential spawning areas dominated by gravel

Distribution: 

Distribution: Chum salmon have been recorded spawning in streams in Korea north along the Arctic coast of Russia, and from the Mackenzie River on the Canadian Arctic coast of North America southward into central California. They have been caught in the ocean as far south as San Diego, but the southernmost freshwater record has been the San Lorenzo River, Santa Cruz County (Moyle 2002). Historically, they were reported to be present in most streams north of San Francisco Bay, although the evidence is anecdotal. At present, they become progressively less common in southern streams within their historic range but they are still present in small numbers in some Oregon streams, as well as in California (Moyle 2002).
In California, chum salmon are commonly taken in the commercial salmon fishery but records of their regular occurrence in fresh water are sporadic. Historically, they were considered to have small spawning runs in the Sacramento and Klamath (Trinity) rivers (Mills et al. 1997) and fish were commonly observed in other coastal rivers as well. During a ten-year (1949-1958) survey of the Sacramento River system, 68 chum salmon were recorded, leading Hallock and Fry (1967) to conclude that a very small run was present. A few spawners still are observed in the Sacramento River but not every year. In recent years, small numbers of adults have been recorded from two San Francisco Bay tributaries and in 2004 and 2005, juveniles were collected from the lower Napa River during a fish monitoring program (Leidy 2007).
Chum salmon are observed in the Klamath and Trinity rivers on a regular basis. The California Academy of Sciences has a small collection of parr taken from the Klamath River in 1944. Screw traps set in the rivers catch juvenile chum salmon on an annual basis, at least when they are looked for (Moyle 2002), suggesting small runs still exist. Adults are also occasionally seen but most are presumably often over looked. Thus a few adults have been observed annually in the South Fork Trinity River, the apparent remnant of a larger run that existed there prior to the 1964 flood (T. Mills, pers. comm. 1995). One adult was seen in the Salmon River ca. 2007 (J. Grunbaum, Klamath National Forest, pers. comm. 2009). Monitoring of Mill Creek, a tributary to the Smith River estuary, by J. Waldvogel (2006) suggests that chum salmon spawn there on a regular basis, based on the occurrence of adults, juveniles, and smolts (Stillwater Sciences 2002). They occur often enough to suggest that there may be a small annual run in the lower Smith River. Three adults were caught in the Rowdy Creek Hatchery trap (Smith River, one per year in three consecutive years (A. Van Scoyk, Rowdy Creek Hatchery, pers. comm. 2009) from 1994-1999. Chum salmon are also observed on an irregular basis in other coastal streams, such as Redwood and Lagunitas creeks in Marin County (Ettlinger et al. 2005) and Prairie Creek in Humboldt County (R. Bellmer, pers. comm. 2010). Regular surveys of spawning salmon on Lagunitas Creek observed chum salmon every year, including individuals on redds (Ettlinger et al. 2005).

Abundance Trends: 

Trends in Abundance: Chum salmon are abundant from Washington on north, with some runs supported by hatchery production (Johnson et al. 1997). In California they are rare and have probably always been uncommon. There is evidence of spawning in the South Fork Trinity. In the period 1985-1990, 1-3 adults were seen or captured every year except 1988 and juveniles were taken on at least six occasions; one pair was observed spawning in 1987, and one fish caught in 1990 was spawned out (Mills et al. 1997). USFWS sampling crews collected 21 chum juveniles and 2 fry in the Trinity River and 4 juveniles in the Klamath Estuary during 1991 (T. Kisanuki, USFWS, unpubl. data), but they are easy to overlook among the thousands of other salmon taken in the traps. In the West Branch of Mill Creek, a tributary of the Smith River, 1-8 spawning chums were observed in each of 10 years between 1980-2002, entering the stream during early to mid-December during high stream flows, a period when Chinook salmon were also entering (Waldvogel 2006). In 2001-2002, both adults and juveniles were observed (Stillwater Sciences 2002). The fact that Mill Creek has had chum spawning reported for so many years is presumably in part a function of observers being present and in part a function of its estuarine position, an attractive location for chum salmon. Even though they are not observed every year, the frequency of observations suggests that alternate spawning areas may also be present in the main stem Smith River or its other tributary streams during years when spawning habitat is not accessible in Mill Creek.
There apparently was once a small run in the Sacramento River, with spawner estimates of 34-210 fish annually in the 1950s (Mills et al.1997). But subsequent records have been spotty (Moyle 2002) and they are rarely seen in salmon surveys. Curiously, chum salmon juveniles were found in 2006 in the Napa River, indicating successful spawning (Martin 2007).
Overall, it appears chum salmon spawn, at least sporadically, in streams from San Francisco Bay north to the Oregon border. The evidence suggests, however, that the only California rivers currently used by chum salmon for spawning on a regular basis are the South Fork Trinity, Klamath and Smith rivers, although the numbers of fish in each river is small. There may also be small numbers on a regular basis in Redwood and Prairie Creeks, Humboldt County. It is highly likely that chum salmon were more abundant and widely distributed in the past. However, chum salmon abundance has always been low compared to other salmon, few observers are aware of them, and juveniles are easy to overlook, so there is no real trend data available on their abundance. It is reasonable to think, however, that they once maintained small populations in the Sacramento River and various coastal rivers that have been extirpated in the last 50-70 years and that existing populations are likely to be extirpated in the near future.
Based on the evidence presented above, it is possible that the number of chum salmon spawning annually in California is 100-500 fish, divided among 3-4 streams. Historic numbers, in contrast, were in likely in the thousands, with dozens of streams having small runs.

Description: 

Description: Chum salmon reach up to 1 m TL and 20.8 kg, but in California they are typically