Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii)

Cutthroat Trout
Cutthroat Trout
(©fisheyeguyphotography)
Juvenile Cutthroat Trout
Juvenile Cutthroat Trout
Klamath River Estuary
(courtesy of Mike Wallace, CDFW)
Coastal Cutthroat
Coastal Cutthroat Trout
(courtesy of Mike Dean, CDFW)

Introduction

Coastal cutthroat trout (Oncorhynchus clarkii clarkii) are native trout subspecies found in the coastal streams of North America from the Eel River in northern California to south central Alaska. They occupy small coastal streams, rivers, and lakes and are closely associated with the temperate rain forests of the Pacific Northwest. They are the only subspecies of cutthroat trout that is anadromous. They are renowned for their complex life history that includes resident, river migrant, lake migrant, and marine migrant forms. Anadromous coastal cutthroat trout, sometimes referred to as “sea-runs” can be found in the estuaries and lagoon systems of northern California. Coastal cutthroat trout spawn in small headwater streams, for the most part, above the spawning grounds of other Pacific salmon. They are important ecologically and are a popular sport fish.

Protection Status

State Listings
California state species protection status listings are governed by the California Endangered Species Act (CESA).
- No special status.

Federal Listings
Federal species protection status listings are governed by the Endangered Species Act (ESA).
- No special status.

Critical Habitat
The Endangered Species Act (ESA) requires the federal government to designate critical habitat for any species it lists under the ESA.
- No designated Critical Habitat

Recovery Plans

As a non-listed species there is currently no recovery plan in place for coastal cutthroat trout. Representatives from California Department of Fish and Wildlife participate in an interagency team, the Coastal Cutthroat Trout Interagency Committee. The team is working on coordinating efforts for improved management and monitoring of the subspecies in California and throughout the geographic range of the subspecies.

Identification

Size and Weight Range
Spawning adult size range: Anadromous forms rarely exceed 40 cm fork length (FL) but individuals reaching 70 cm have been recorded. It is uncommon for individuals from landlocked populations to exceed 30 cm FL.
Spawning adult weight range: Anadromous forms rarely exceed 2 kg (4.4 lbs) but individuals reaching 8 kg (17.6 lbs) have been recorded.

Fin Characteristics
Dorsal fin: 9 to 11 rays
Anal fin: 8 to 12 rays
Pectoral fin: 12 to 15 rays
Pelvic fin: 9 to 10 rays

Scales
Scales are smaller than those of rainbow trout, with 140-200 along the lateral line (Behnke 1992).

Lateral Line
140-200 scales along the lateral line (Behnke 1992). Parr possess 9-10 widely spaced parr marks along the lateral line.

Branchiostegal rays
9 to 12 on either side of the jaw.

Gill rakers
15 to 28 gill rakers on each arch.

Juvenile Description
Juvenile cutthroat have 9 to 10 oval parr marks that center on the lateral line. The spaces between the parr marks are wider than the parr marks. Black speckles are present on the parr marks dorsally. Aside from a dark leading edge on the dorsal fin and a few spots on the adipose fin the fins are generally plain.

Adult Description
Numerous black body spot and yellow to red slashes of pigment under each side of the lower jaw are defining features of Cutthroat trout. Spots are also frequently present on the anal and paired fins. The body spotting becomes nearly invisible when fish become silvery during migrations to and from sea. They possess basibranchial teeth which can be easily felt. 
Coastal cutthroat trout are similar to rainbow trout in body color but spotting is heavier particularly below the lateral line and on the posterior half of the body. Cutthroat trout also have longer maxillary bones (larger mouths) that extend beyond the eye and more slender bodies than rainbow trout.

Life History

Migration
Coastal cutthroat trout possess variable life history strategies (DeWitt 1954; Pauley et al. 1989, Moyle 2002). This plasticity is among the most extreme in Pacific salmonids and variations in migratory behavior are found both between and within populations. Trotter (2007) puts this diversity into four main groups: (1) amphidromous (sea-run) life history, (2) lacustrine life history, (3) riverine (potadromous) life history, and (4) stream-resident. The amphidromous forms are not considered strictly anadromous because they can move back and forth between fresh and salt water multiple times to feed [often on other salmonids] although they also migrate into fresh water to spawn. Lacustrine coastal cutthroat use large lakes like the ocean (but do not occur in California). Potadromous forms are found in rivers and make seasonal migrations up and down the rivers. Resident populations are typically found above natural barriers, in headwaters. Offspring of resident fish can become amphidromous and vice versa (Trotter 2007). The Smith and Klamath rivers in California have both amphidromous populations and resident populations isolated in small streams upstream of barriers (e.g., Little Jones and Tectah creeks.) When multiple forms coexist, temporal and spatial segregation presumably influence genetic structure of the population and may lead to genetic differentiation between sympatric ecotypes within a watershed. Environmental conditions that affect growth rate, such as food availability, water quality, and temperature markedly influence migratory behavior and residency time (Hindar et al. 1991, Northcote 1992, Johnson et al. 1999). Johnson et al. (1999) noted that the large variability in migratory behavior may be due to habitat being most available for cutthroat trout at times when it is not being used by more rigidly anadromous salmonids; this flexibility may release cutthroat trout from competition and predation pressures at certain times of year, while allowing them to track the movements of juvenile salmonids as prey (Trotter 2007).

Spawning and Egg Development
Anadromous coastal cutthroat trout spawn first at 2 to 4 years of age and may return 2 to 5 times to overwinter and spawn. In northern California their migration up spawning streams begins following the first substantial rainfall which usually occurs between August and October. Coastal cutthroat trout have ecological requirements analogous to those of resident rainbow trout and steelhead. When the two species co-occur, cutthroat trout occupy smaller tributary streams while the competitively dominant steelhead occupy larger tributaries and rivers. As a consequence, cutthroat trout tend to spawn and rear higher in watersheds than steelhead. Their life spans are 4-7 years, with non-migratory fish often reaching sexual maturity earlier and at a smaller size than anadromous fish (Trotter 1991, Johnson et al. 1999). Resident fish generally reach sexual maturity between the ages of 2 and 3 years whereas sea-run fish rarely spawn before age 4 (Johnson et al. 1999). Sexually mature trout can demonstrate precise homing capabilities in their migrations to natal streams. In northern California, coastal cutthroat trout migrate upstream to spawn after the first significant rain, beginning in fall. Peak spawning occurs in December in larger streams and January to February in smaller streams (Johnson et al. 1999). Ripe or nearly ripe females have been caught from September to April in California streams, indicating a prolonged spawning period.
Females dig redds in clean gravels with their tails predominantly in the tails of pools in low gradient reaches, often with low flows (less than 0.3 m3/second summer flows) (Johnston 1982, Johnson et al.1999, Trotter 2007). The completed redds average around 35 cm in diameter by 10-12 cm deep. After spawning is completed, the female covers her redd with about 15-20 cm of gravel. Each female may mate with numerous males. Fecundity ranges from 1,100 to 1,700 eggs for females between 20 and 40 cm TL and increases with the size and age of females. Coastal cutthroat trout are iteroparous with a higher incidence of repeat spawning than steelhead. They can spawn every year but post-spawning mortality can be quite high. Maximum age recorded for coastal cutthroat is 14 years, from Sand Creek, Oregon (Trotter 2007).
Eggs hatch after 6-7 weeks of incubation, depending on temperature.

Fry and Juveniles
While their yolk sac is absorbed alevins remain in the gravel for an additional 1 to 2 weeks. Alevins emerge as fry between March and June, with peak emergence during mid-April, then spend the summer in backwaters and stream margins (Johnson et al. 1999). Juveniles remain in the upper watershed until approximately 1 year in age at which point they may move extensively throughout the watershed. Once this age is reached, it is difficult to determine the difference between sea-bound smolts and silvery parr moving back up into the watershed (Johnson et al. 1999).

Smolt Emigration and Cutthroat in the Ocean
Sea-run cutthroat trout generally make their first migrations when two to three years old, although they can enter sea water as late as their fifth year. The amphidromous forms are not considered strictly anadromous because they can move back and forth between fresh and salt water multiple times to feed [often on other salmonids] although they also migrate into fresh water to spawn. Smolts or adults entering the saltwater environment remain close to the shore and do not normally venture more than about 7 km from the edge of the coast (Johnson et al. 1999). Typically, they stay in or close to the plume of the river in which they were reared (Trotter 2007). Individuals can spend prolonged periods (months) in estuaries, often moving in and out of fresh water, likely taking advantage of different feeding and rearing habitats.
In the marine environment, cutthroat trout feed on various crustaceans and fishes, including Pacific sand lance (Ammodytes hexapterus), salmonids, herring and sculpins. Marine predators include Pacific hake (Merluccius productus), spiny dogfish (Squalus acanthias), harbor seals (Phoca vitulina) and adult salmon (Pauley et al. 1989).

Habitat

Coastal cutthroat trout require cool, clean water with plenty of cover and deep pools for holding in summer. They prefer small, low gradient coastal streams and estuarine habitats, including lagoons. Adults overwintering in streams, rather than estuaries, prefer pools with fallen logs or undercut banks but will also utilize boulders, depth, and turbulence as alternative forms of cover if woody debris is not available (Gerstung 1998, Rosenfeld et al. 2000, Rosenfeld and Boss 2001). Optimal stream temperatures are less than 18°C, with preferred temperatures being around 9-12°C. This may explain why they occur mainly in more northern streams in California, within the coastal fog belt. Coastal cutthroat require high dissolved oxygen levels and will avoid areas with less than 5 mg/L DO in summer months (Pauley et al. 1989). Feeding and movement of adults are impaired at turbidities of greater than 35 ppm. In some locations coastal cutthroat trout populations can be found above natural waterfalls which are barriers to other anadromous fish.

Spawning Females
Spawning takes place in small streams with small to moderate sized gravel ranging from 0.16-10.2 cm in diameter. Cutthroat preferentially use riffles and the tails of pools for spawning with velocities of 0.3-0.9 m/sec, although they have been observed spawning in velocities as low as 0.01-0.03 in small streams in Oregon (Pauley et al. 1989). Spawning has been recorded at temperatures of 6-17° C, with preferred temperatures of 9-12° C (Pauley et al. 1989, Moyle 2002). Embryo survival is greatly reduced at turbidities greater than 103 ppm and dissolved oxygen levels <6.9 mg/l.

Fry
Preferred water velocities for fry are less than 0.30 m/sec, with an optimal velocity of 0.08 m/sec (Pauley et al. 1989).

Parr (juveniles)
Juveniles generally rear in smaller streams with dense overhead cover and cool summer temperatures (Rosenfeld et al. 2000, 2002).

Fishing Regulations

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