The Coastal Cutthroat Trout

A sea-run cutthroat, begining to assume its river coloration. The red slashes on the throat of the fish develop only when it returns from the sea to spawn; later the scales take on a brassy tinge.
Freshwater forms usually have the red slashes throughout their lives.
Study/watercolour

Of the three varieties of sea trout, only the sea-run cutthroat Salmo clarki clarki is smaller than its freshwater relatives. The steelhead grows much larger than the average lake and river rainbow; the Atlantic sea trout far outstrips the average brown trout. It is easy to assume that because the sea is so bountiful in food resources, any sea-going trout will quickly grow big and fat. Yet the average sea-run cutthroat weighs little more than a pound, three pounders are quite scarce, and a five pounder is, in angling terms, the fish of a lifetime. River cutthroats are of comparable size, and lake cutthroats may grow much bigger.

Sea-run cutthroat trout are widespread along the Pacific coast of North America, from Alaska to the Queen Charlotte Islands and British Columbia (including Vancouver Island) south through the United States seaboard to California. Few rivers and streams are without them. . Smolt migration occurs in late April and May in California, in May and June in Oregon and Washington State, and up to the end of July in British Columbia and Alaska. These smolts join into shoals with those cutthroats that have previously spawned to feed on smaller fish such as Pacific herrings and anchovies, and crustaceans such as shrimps and euphausid prawns. Within three months of reaching the sea, an eight inch cutthroat smolt will have attained a length of twelve inches.

Unlike Atlantic sea trout and steelheads, however, cutthroat trout never move far from their natal river estuary; and rarely will they cross areas of very deep seawater, preferring to hug the shoreline and feed over sand and gravel in little more than ten feet of water. Furthermore, they spend far less time in the sea than either of the other varieties. With the exception of a small proportion of cutthroats from the north of their range (Alaska and, possibly, British Columbia), the entire sea-run population returns to freshwater in late summer and autumn.

The older and larger fish, which have spawned in previous years, return to the estuaries first. By September all have left the sea and are in the estuaries or have run the river. They continue to feed throughout this return journey, taking crustaceans and small fish such as sculpins from the estuary, and caddis larvae and stonefly and mayfly nymphs from the freshwater. Once they have reached the spawning streams, feeding virtually ceases as mating begins.

Though not all cutthroats spawn on their first return to freshwater, they will remain in the river throughout the spawning period, until the whole population moves down to the sea once more in April and May. Thus the sea-run cutthroat has on average only four or five months of sea-feeding each year after leaving the river as a smolt.

In the far north, however, some Alaskan sea-run cutthroat trout do overwinter in the sea following their initial seaward migration as smolts. Eight such fish, which made their maiden runs after a winter at sea weighed between 1 and 3 lbs. The smallest had spent two years in the river and was thus three years old when it was caught; the largest fish had spent three years in the river before it left for the sea and was thus four years old. A three year old cutthroat from the rivers of Oregon and Washington would weigh about 1 lb; and a 3 lb. fish from these waters would be at least six years old.

Cutthroat trout in lakes and rivers can easily be identified by the red flashes on either side of the throat. In the sea-run form these markings are not so clear, just a slight flush of very pale orange or cream when the fish are in the sea and immediately after they have returned to freshwater. Superficially they resemble the freshwater rainbow or small herling steelhead. However, the more extensive spotting over the body of the cutthroat, with the exception of a narrow silver-white band on the underside between the pectoral and pelvic fins, is quite characteristic. For certain identification it is necessary to examine the tongue: the base of the tongue of the cutthroat has conspicuous hyoid teeth

The colours change rapidly when the cutthroat returns to the river. Its silver flanks turn to yellow-brown; its pale blue-green back turns a darker olive green; the spotting becomes more conspicuous. Above all, the faint orange on the throat becomes a vivid rich orange-red, the mark of the cutthroat.

For many years, the sea-run cutthroat stocks were reduced in some waters by pollution, habitat destruction or over-fishing. Because the cutthroat was economically unimportant, no effort was made to supplement the natural spawning with hatchery reared fish. In Sea-Run (1979), Les Johnson of Gig Harbor, Washington State, described a happier prospect. At Alsea River in Oregon and on the coast near Manchester, Washington, are two hatcheries that raise cutthroats to smolt stage. Furthermore, throughout the range of the migratory cutthroat there is an increasing trend to impose bag limits and encourage catch-and-release. It is hoped that this trend will continue, for the little sea-run cutthroat deserves careful conservation.