Chum Salmon, information from Fairbanks Fishery Resources Office
General Description
Chum salmon, Oncorhynchus keta, are also sometimes known as dog or calico salmon. They have the widest distribution worldwide of any of the Pacific salmon. The Yukon River in Alaska and Canada produces the largest runs of chum salmon in North America.
Ocean stage chum salmon are metallic greenish-blue along the back with black speckles. They closely resemble both sockeye and coho salmon at this stage. As chum salmon enter fresh water, their color and appearance changes dramatically. Both sexes develop a "tiger stripe" pattern of bold red and black stripes. Males develop a hooked snout and prominent teeth.
Chum salmon typically spawn in coastal rivers. Only the Yukon River in North America and the Amur River in Russia have chum populations that are long-distance travelers. These fish can migrate over two thousand miles to their spawning streams.
Life History
There are two life history forms of chum salmon in the Yukon River known as summer chums and fall chums. Fall chums are larger, heavier fish, and tend to be older when they return to spawn. Fall chums also enter the Yukon later and generally spawn farther up the river.
Chum salmon can return to spawn at between 3 and 6 years of age. Summer chum salmon enter the Yukon on their spawning migrations from late May through mid-July. Fall chum salmon enter the river from late June through early September. Summer chum salmon lay about 2,500 eggs, fall chum salmon lay over 3,300.
Chum salmon eggs in interior Alaska hatch while rivers and streams are still ice covered. Chum salmon begin migration to the sea soon after emerging from the gravel in the spring. Fry stay in river estuaries for several months, then move into the open ocean in the fall and winter of their first year. Most Alaskan chum salmon stay at sea for 2 to 5 years. As they near spawning age, chum salmon start moving toward their home streams.
Economic Importance
Until a few years ago, chum salmon were the least commercially utilized of the Pacific salmon. Since then, a growing market has developed in Japan and Europe for fresh and frozen fish and roe. Over * 280,000 pounds of chum salmon and over 84,000 pounds roe were harvested annually from the Yukon River in recent years. The combined worth of these products is in excess of 1.1 million dollars.
Most chum salmon are caught with purse seines and gill nets in the ocean. Fish wheels and gill nets are used to catch fish swimming upriver.
Cultural Importance
Chum salmon have always been an important source of food for native people and their dogs in over 200 rural villages in interior Alaska. Along the Yukon River, over * 230,000 chum salmon were caught by subsistence fishermen in 1997. These fish are caught with gill nets and fish wheels and are smoked, dried, or frozen for winter subsistence use.
Salmon Eggs
In the upper Yukon drainage, chum salmon select spawning sites in springs or groundwater seepages to prevent the redds (nests) from freezing. Summer chums lay about 2,500 eggs, fall chums lay over 3,300. Chum salmon eggs in the Yukon River drainage hatch from December to February while rivers and streams are still ice covered.
Low oxygen levels, water pollution, and predation by fish, insects and birds are all threats at this stage. Excess sediment in the water is extremely dangerous as it can smother eggs or cover the redd trapping fish inside.
Alevin
A newly hatched salmon is called an alevin. At this stage, it looks like a thread with eyes and an enormous yolk sack which provides all nutrition for the fish in the first weeks of its life.
As soon as the yolk sac is absorbed, chum salmon make their way up through the gravel and immediately begin migration to the sea. In Alaska's interior, this migration often coincides with the ice going out on the rivers.
Alevin require cold, clear, oxygen-rich water. Excessive sediment in the water is one of the greatest dangers to salmon at this stage. It can reduce oxygen levels and cover the top of the redd, trapping the fish inside. Aquatic insects and other fish are the primary predators.
Chum Salmon Fry
Chum salmon fry start their journey to the ocean soon after emerging from the redd. Imagine a fish barely an inch long battling the current in the Yukon River! This downstream migration can start with spring ice break-up on Interior rivers and continue into early summer.
Chum fry form into schools once they reach the river estuaries. They stay in shallow water for several weeks feeding on insect larvae and marine invertebrates, then move farther into the estuary. The fish move into the open ocean by fall.
Chum Salmon Smolt
Many physical changes occur in a young salmon to help it make the transition from a freshwater to saltwater existence. This process is called smolting. The small fish replaces its parr marks, a pattern of vertical bars and spots useful for camouflaging the fry in fresh water, with the dark back and light belly coloration used by fish living in open water. The gills and kidneys change so that they can process salt water.
Smolting isn't as pronounced in chum salmon compared to other salmon species, since they have such a short fresh-water residence period. The small fish can tolerate low salt concentrations when they reach the estuary in the early spring This tolerance grows rapidly until they are able to move into the open ocean by fall.
Ocean Stage Adult
Most Alaskan chum salmon stay at sea for 2 to 5 years. During their ocean existence, their primary diet consists of copepods, fish, mollusks, squid and tunicates.
Chum salmon from Interior rivers start moving into the open ocean in the fall and winter of their first year. They leave the Bering Sea and swing south east through the Aleutian chain into the Gulf of Alaska. During the following spring and summer, they travel north and west again. As they near spawning age at 3 to 6 years, chum salmon start moving toward their spawning streams.
Spawning Stage
Alaskan chum salmon can return to spawn at between 3 and 6 years of age. There are two distinct spawning runs in the Yukon River known as summer and fall chums. Summer chum salmon enter the river in late May or June with fall chum salmon following in late June or July. The fall chum salmon are larger, fatter, and contain higher quality meat than the summer chum salmon. Some fall chum salmon travel all the way up to the headwaters of the Yukon River in Teslin Lake, 3,200 km from the river mouth.
Summer chum salmon lay about 2,500 eggs, fall chum salmon over 3,300. In the upper Yukon drainage, chum salmon select spawning sites in springs or groundwater seepages to prevent the redds (nests) from freezing during the winter months. Female fish rapidly pump their tails to wash out a depression in the stream gravels. As she deposits her eggs, they are fertilized by the male. The female salmon then uses the same tail movements to completely cover the eggs with gravel.
Text by USFWS staff
Graphics by Canada Department of Fisheries & Oceans
Pacific Region Communications Branch
Last modified 25 July, 2001
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