The size range of pink salmon does not vary as greatly as those of other Pacific salmon due to the uniform rate of maturity at 2 years. Size differences are a function of the abundance of the fish in the year classes. Most range between 3-5 pounds, but may reach a bit over 10 pounds maximum. Pinks rank as the smallest of the Pacific salmon, but they are the most plentiful in their range.
The body is elongate, depth about 4 into standard length, and moderately compressed. Head length is about 4 into standard length, and conical. Mouth is large and directed forward and upward. The upper jaw reaches beyond the posterior margin of the orbit. Snout is narrowly rounded in profile. Lips are fleshy. Teeth are small and weak in both jaws (teeth and snout undergo disproportionate growth in breeding males), on the head and shaft of the vomer, palatines, and the tongue, however there are no teeth on the basibranchials.
The interorbital space is high, wide, convex and rounded, its’s width about 3.1 into the length of the head. Eye diameter is about 6.3 into head length. Gill membranes are free of each other and of the isthmus. Branchiostegals range from 10 to 15. Caudal peduncle is moderately compressed, its least depth about 12 into standard length. Pyloric caecae range from 165 to 195. The first gill arch has from 24 to 35 gill rakers. Scales are cycloid with 170 to 229 scales above the lateral line, and 150 to 205 on the lateral line.
Adipose fin is small, slender, and fleshy. The number of rays in each of the fins are: dorsal, 10-15; anal, 13-17; pectorals, about 15; and, pelvics, about 10 (each of the abdominal fins have a free tipped fleshy appendage above its insertion). The caudal fin is slightly forked.
In spawning males the snout becomes elongate and hooked, the teeth enlarge, and a prominent hump forms behind the head, suggesting the common name “humpback”. In spawning females these characteristics are absent or weakly developed.
Range: In the pinks ocean phase they can be differentiated from other young salmon especially immature chinooks which they are commonly mistaken for by the very large spots along the back (largest spots of any salmon) and large oval black blotches on both caudal (tail) lobes. The ocean phase coloration is silvery with a metallic blue back; the body is compressed looking. It is during the spawning phase that male pinks develop a tremendous hump at the shoulder much more exaggerated than in other salmon species and a fierce-looking hooked snout, sporting dagger-like canine teeth. (These teeth are not merely ornamental but can inflict severe damage among fighting males.) The male’s body color changes to dull brown or rust. The females are quite distinct looking from the males; they have no humped back appearance, they have greenish to olive brown sides and large ovate spots. The numerous large spots so prominent in the ocean phase generally become much less accentuated during the spawning cycle.
Distribution: Streams as far north as Korea have spawning runs of pinks. In North America, pinks spawn as far north as the Mackenzie River, Canada, and in many Alaskan streams, as well as in Aleutian Island streams. British Columbia’s Fraser River becomes thick with these aggressive fish during the month of August and early September. Pink salmon are ready to spawn at two years of age, most of which time has been spent at sea. This unusual rate of uniform maturity causes the runs sizes to vary in number from one year to the next. Odd and even years will show a consistent contrast with commonly large commercial catches taken during alternate years and smaller catches in between. Depending upon the stream or river site, temperatures and other environmental factors, pinks will begin entering streams as early as mid-June to as late as October with most spawning taking place in late September through November. Pinks are a short running salmon, often spawning in inter- tidal areas where brackish or even saltish waters do not seem to affect the eggs adversely to any material degree. A few fish have been known to migrate several hundred miles, but most migrate only a few miles. Spawning sites are usually in moderate-sized streams over gravel riffles in relatively shallow water. A series of redds is dug by the females with each redd getting its share of fertilized eggs. During the redd building, accompanying males can fight savagely and, as mentioned earlier, can inflict deep wounds with those jagged canine teeth. After the female has laid her cargo of between 1,200 to 2,000 eggs, she will last no more than a couple of days before death makes its claim. The males also die.