King salmon, also called Chinook salmon (Oncorhynchus tshawytscha) are the largest Pacific salmon, and they are also the least abundant of the Pacific salmon species. Adult kings average 24 to 36 inches (61 to 91 cm) in length but may be as long as 58 inches (150 cm). They average 10 to 50 lbs. (4.5 to 22.7 kg) but sometimes grow much larger. The world record sport-caught king, caught on May 17th,1985 in the Kenai River in Alaska, weighed 92.25 lbs. (44.11 kg.), and the largest king salmon caught by a commercial fisherman weighed 126 lbs. (57 kg). This fish was caught near Rivers Inlet, British Columbia in the 1970s.
King salmon can be distinguished from other Pacific salmon species by the black spots present on their head and on both the upper and lower lobes of the tail and by their black gums. In their marine phase, kings are dark green to blue on the top of the head and back and silver to white on the sides, belly, and tail. When they return to fresh water to breed, they turn olive brown, red, or purple in color. Males are more brightly colored than females. In the ocean, kings are torpedo-shaped with a heavy mid-section and a blunt nose. During their breeding phase, males develop a hooked nose and enlarged teeth. Fry can be identified by well-developed parr marks extending below the lateral line. When they become smolt and are headed for the ocean, they have bright, silver sides, and the parr marks recede to above the lateral line.
In North America, king salmon range from Monterey Bay in California to the Chukchi Sea in Alaska. On the Asian coast, kings occur from the Anadyr River in Siberia to Hokkaido, Japan. In Alaska, they are most abundant in the Yukon, Kuskokwim, Nushagak, Susitna, Kenai, Copper, Alsek, Taku, and Susitna Rivers. Kings have been introduced to many areas, including the Great Lakes of North America, Patagonia, and New Zealand. King salmon are raised in pens in New Zealand and are an important export for the country.
King salmon spawn in fewer rivers than other Pacific salmon because they require larger, deeper rivers and spawn only in areas with good water flow through the gravel. They migrate from the ocean back to their birth streams in the winter and early spring, and while some enter fresh water as early as May, most enter streams in late June or early July. Most Alaska rivers receive only a single run of kings each year. Usually, those entering the streams first are the ones that will travel the furthest. Yukon River kings may travel more than 2000 miles (3219 km) to the headwaters of the Yukon River to spawn.
When a female king arrives in the spawning area, she selects a spot for her nest. She swims to the bottom of the stream, turns on her side and gives several powerful thrusts with her tail to remove gravel from the stream bottom. She continues to dig, resting occasionally, until she has a long, deep nest. While she is digging her nest, she drives off any other females that approach but pays little attention to the males. She is usually accompanied by a dominant male and one or two subordinate males. The dominant male, and occasionally one of the subordinate males, drive off any other male intruders. The males do not help with the nest digging, but the dominant male may court the female by resting beside her and quivering or by swimming over her and touching her dorsal fin with his body and fins.
When the nest is finished, the female drops into it followed by the dominant male and sometimes one or more of the subordinate males. The fish open their mouths, quiver, and release their eggs and sperm. The female then swims to the upstream end of the nest and begins digging a second nest, covering the eggs in the first nest with the gravel she unearths for the second nest. She continues digging four or five nests or more over the next several days and lays between 3,000 and 14,000 eggs. Even after all her eggs are laid, she continues digging in a haphazard manner until she weakens and dies. The male may mate with another female, but he also will soon die.
In Alaska, king salmon eggs hatch in the late winter or early spring, depending both on when they were laid and the temperature of the water. The hatchlings are called alevins, and they live in the gravel for several weeks, receiving nutrition from their attached yolk sac. Two to three weeks later, the young fry, as they are now called, wiggle up through the gravel and begin to feed on their own. Fry in fresh water feed on plankton and insects. Some kings, called “ocean-type,” migrate to saltwater during their first year. “Stream-type” kings remain in fresh water for one or even two years. In Alaska, most kings remain in fresh water one year and then migrate to the ocean as smolts the following spring.
In the ocean, king salmon eat herring, pilchard, sandlance, squid, crustaceans, and other organisms. They are voracious feeders, and they grow rapidly in the ocean, often doubling their weight in just one summer. Most king salmon have pink or red meat, but 3% of all kings have white meat. In Southeast Alaska, as many as 40% of the kings in some runs have white flesh. Biologists are unsure whether the variable meat color is due to genetics or to what the fish eat.
Kings become sexually mature anywhere from their second to their seventh year, so they vary greatly in size when they return to spawn. A mature three-year-old king, called a “jack,” would weigh less than four pounds (1.8 kg) while a mature seven-year-old would probably weigh more than fifty pounds (22.7 kg). Males mature earlier than females, so most jacks are males, and in many spawning runs, males outnumber females in all but the six-and-seven-year age groups.
King salmon are considered relatively uncommon but not rare in Alaska, but in some rivers their numbers have dropped drastically in the past few years. Over the next two weeks, I’ll write about the various fisheries for kings and the controversies swirling around them.
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