Oncorhynchus clarki clarki
An anadromous coastal cutthroat from Washington State's Puget Sound.
The coastal cutthroat is a major subspecies of cutthroat trout that is native to the west coast of North America, for about 2,000 miles from the Eel River in northern California to the Prince William Sound in southern Alaska (See Map). Coastal cutthroat are the only subspecies of cutthroat to utilize the marine environment during its life history. However unlike other anadromous salmonids, coastal cutthroat do not attain a very large size in marine waters with an apparent maximum size of around 6-7 pounds.
Coastal cutthroat exhibit a wide variety of life history strategies with stream resident, fluvial, lacustrine and anadromous populations occurring across their native range. While steelhead or salmon typically travel hundreds or even thousands of miles during their time at sea, coastal cutthroat are more of home bodies and tend to stay within the confines of the estuary. While in the marine environment coastal cutthroat tend to prefer shallower near shore waters between ten and twenty feet deep. As a general rule cutthroat stay within about five miles of their natal streams but have been found as far as forty miles off shore and in water 100 feet deep off of the Columbia River estuary (Behnke 2002). While in the in the marine environment, coastal cutthroat feed heavily on baitfish such as sand lance, sculpin, salmon fry, and herring. Krill and other small crustaceans also make up a substantial portion of their diet, especially for cutthroat overwintering in the saltwater. Unlike most anadromous fish, coastal cutthroat do not attain overly large sizes, with a maximum size of around 24 inches and six pounds.
Anadromous coastal cutthroat show a great amount of diversity throughout their native range, with run timings and habits being highly variable. Generally these fish will spend less than a year in the marine environment before returning to their natal streams to spawn. However this is not always the case and in the Puget Sound some cutthroat have been known to skip spawning and overwinter in the saltwater. Many other populations may return to freshwater simply to overwinter and may or may not spawn upon returning. The time of return to fresh water varies greatly and in some case there may be two separate run timings of sea-run fish in the same watershed. The Stillaguamish River is noted for having an early run that arrives in late summer through fall and a later run arriving from December through March (Behnke 2002). This early run timing is common to the larger rivers around the Northwest and also coincides with the return of spawning Pacific salmon, whose eggs the cutthroat feed heavily on. The later run timing is typically more common in small streams feeding directly to the saltwater (Trotter 2008).
Like all Pacific trout, coastal cutthroat are iteroparous meaning that they can spawn more than once. The survival rate for cutthroat returning to spawn a second time is relative high (up to 40%) and they have been documented to spawn as many as five times during the course of their life (Behnke 2002). In the Columbia River up to 50% of returning fish are either first spawners or non-spawning overwintering fish that had returned to spawn during a previous year (SEI Panel 2001). Coastal cutthroat are Winter-Spring spawning fish, with the spawning period extending from December through May. In the southern part of their range from British Columbia to California, the bulk of the cutthroat spawn in February but in Alaska April or May spawning is more common (Trotter 1989). Much of this spawning occurs in small streams, which contribute a disproportionate amount of rearing habitat for juvenile coastal cutthroat when compared with larger streams (Rosenfeld et al. 2002). Smolts typically enter the salt water from March to June at an age of two to five years old, with later timing and older ages for smolts found in the northern part of their range (Trotter 2008 and Johnson et al. 1999). Kelts, which are spawning fish that are returning to the saltwater, generally migrate out to sea around the same time as the smolts. This timing coincides with the out migration of juvenile salmon which provide an important food source for sea-run cutthroat.
Populations of fluvial and lacustrine cutthroat exhibit habits that a similar to those of anadromous fish, but migrate to a river or lake instead of the marine environment. Lacustrine and fluvial fish have are opportunistic feeders, with their diets be made up of other fish, salmon eggs and aquatic and terrestrial insects. These fish show similar patterns of migration to and from spawning stream as what are found in anadromous populations and also are highly dependent on small streams as rearing habitat (Saiget et al. 2007). Lake adapted coastal cutthroat have the potential of attaining the largest size of any life history form of coastal cutthroat. A unique lacustrine population of coastal cutthroat occurs in Crescent Lake in Olympic National Park, where individuals have been recorded up to twelve pounds. These fish were cut off from access to the sea and other populations of cutthroat by a massive landslide. At one time these fish were considered to be a unique subspecies known as the Crescenti cutthroat (Oncorhynchus clarki crescent), due to their unique silvery appearance. However studies have shown that these fish are simply an isolated lacustrine coastal cutthroat population (Behnke 1992). Migratory coastal cutthroat have a life span of between seven and nine years. Populations of stream resident cutthroat often occur above barrier falls and have a diet made up of both aquatic and terrestrial insects and generally attain a maximum size of about twelve inches.
Unlike other subspecies of cutthroat trout, the coastal cutthroat has managed to maintain a hold across their entire native range. However this is not to say that they have not suffered declines since the arrival of Euro-Americans and this is especially true for the migratory life history types of these fish, which are now depressed across much of their native range. Today some populations are so depressed that they have been listed under the Endangered Species Act and others have gone extinct all together. According to Johnson et al. (1994) the Umpqua River's coastal cutthroat population has suffered precipitous declines since the 1950's with returns of sea-run fish numbering below 50 in the early 1990's. As a result the Umpqua River stock was listed as endangered in 1996. However a decision was made to include the Umpqua River stock in with the greater Oregon Coast distinct population segment (DPS) and to include the much more abundant resident populations in with the overall status of each DPS (Johnson et al. 1999). As a result of this decision the still extremely depressed Umpqua River stock of coastal cutthroat was removed from the ESA. Of the known extinct populations, two are found in Washington State and 15 occur in British Columbia (Trotter 2008). In Washington State there are still a lot of questions about the overall status of the coastal cutthroat and the last stock inventory showed that seven populations were depressed, one was healthy and the status of the remaining 32 populations was listed as unknown (WDFW 2000). The threats to coastal cutthroat have come from a variety of issues with the major players being the 4 H's, which were covered in the pages on the five species of Pacific salmon.
Unlike other subspecies of cutthroat trout, coastal cutthroat as a whole have coevolved with coastal rainbow trout throughout their entire native range. Due to this fact, they do not readily hybridize with native rainbows as the two species take advantage of different parts of streams for spawning habitat. However this coexistence between the rainbow and cutthroat trout may break down when hatchery rainbow trout, which have not evolved to coexist with the cutthroat are introduced. Where hybrids are found, they have been shown to occur much more commonly in juvenile fish than adult fish, indicating that there is a negative effect on the fitness of hybrid fish (Johnson et al. 1999). Isolated stream resident coastal cutthroat populations may be extremely susceptible to hybridization with hatchery rainbow trout and within several generations of the introduction of rainbow trout all that often remains of the cutthroat population is a hybrid swarm (Behnke 2002). Where coastal cutthroat occur with other species, rainbow trout and juvenile salmon often generally out compete the cutthroat, resulting in the cutthroat having to utilize less than ideal portions of the stream as habitat.
The native range of the coastal cutthroat is directly tied to occurrence of the Pacific Northwest temperate rainforest and as such these fish have been greatly impacted logging and urbanization across the region. Coastal cutthroat utilize the higher reaches of small tributary streams as spawning and rearing habitat making them very susceptible to population loss due to poor logging practices. A study done by Young et al. (1999) on a clear-cut stream in British Columbia, Canada showed that in stream temperatures rose to lethal levels for cutthroat following the logging. It also took the stream over ten years to fully recover to pre-logging levels. Connolly and Hall (1999) suggested that cutthroat populations in extensively clear cut streams may remain low for fifty years of more due to a lack of large woody debris and shade from conifers. Although commercial fishing for coastal cutthroat does not currently occur, there is some degree of cutthroat by catch in certain salmon fisheries but it is unknown what amount of impact this has on cutthroat populations. Cutthroat from small streams often depend on a low number of spawning adults to maintain the population and can be extremely susceptible to over harvest or mortality associated with fishing. Pauley and Thomas (1993) showed that bait fishing for coastal cutthroat had up to a 58% mortality rate, while the use of spinners had up to a 23% mortality rate after the fish had been released. As such it is important that the proper gear (smaller hooks and preferably flies which have been shown to have the lowest mortality rate) and catch and release methods are followed to minimize mortality of these fish.
Out of all of the subspecies of cutthroat, the appearance of coastal cutthroat shows the least amount of resemblance to the others. The coloration of the back on these fish is generally either greenish-brown or bronze and both anadromous and lacustrine forms tend to have silvery sides with tints of greenish-yellow or golden-yellow. Stream resident coastal cutthroat of may have either a copper or golden-yellow coloration on their sides. As these fish near spawning they become an intense golden yellow color on their sides, which transitions to a dull bronze color as the season progresses. Stream resident fish typically retain violet or purplish color parr marks through adulthood, but these markings fade away on sea-run and lacustrine fish. Coastal cutthroat also can show a rosy color along their lateral line and have a red, orange of crimson slash under their jaws, although these markings may also fade on anadromous fish. A rosy, golden yellow or silvery color is typically found on gill plates which can become intensely colored with red as spawning approaches. Coastal cutthroat often have spots across their entire body, which range in size from tiny to a large size close to that of inland cutthroat. However the spotting pattern can be extremely variable and ranges from very sparse on some fish to so profuse that the spots become interconnected on other fish. The fins are yellow, pink or a reddish-orange color and the anal and pelvic fins may be tipped with white.
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