Animal Diversity Web

Ge­o­graphic Range

Cut­throat trout, On­corhynchus clarkii, are widely dis­trib­uted along the west­ern coast of North Amer­ica. They can be found as far north as Alaska’s Prince William Sound and as far south as Cal­i­for­nia’s Eel River (Willers, 1991). Their range also ex­tends in­land where they can be found on most wa­ter­ways with link­ages to their west­ern range along the Pa­cific coast (Trot­ter, 1987). (Trot­ter, 1987)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Be­cause O. clarkii is such a wide­spread species it oc­cu­pies many dif­fer­ent habi­tats. Cut­throat trout habi­tats range from coastal ma­rine to fresh­wa­ter rivers and streams with gravel sub­strates (Behnke, 1992). The di­ver­sity in habi­tat also leads to a di­ver­sity in the el­e­va­tions in which the species can be found. They occur from moun­tain­ous streams in the Cas­cade, Rocky, and Sierra Nevada moun­tain ranges to the ocean. (Behnke, 1992)

• Habitat Regions
• temperate
• saltwater or marine
• freshwater

• Aquatic Biomes
• pelagic
• lakes and ponds
• rivers and streams
• coastal
• brackish water

• Other Habitat Features
• estuarine

Phys­i­cal De­scrip­tion

There are roughly ten sub­species of cut­throat trout de­scribed by Behnke (1992). They have the same mor­phol­ogy, but their col­oration and spot­ting vary. Coastal cut­throat trout, O. c. clarki, are sil­very to brassy in col­oration with yel­low­ish and ir­reg­u­lar shaped spots. West slope cut­throat trout, O. c. lewisi, are sil­ver in col­oration with a yel­low­ish tint, but can some­times be bright yel­low, or­ange, or red. Their spots are sim­i­lar to those of coastal cut­throat ex­cept they do not ex­tend below the lat­eral line. Yel­low­stone cut­throat trout, O. c. bou­vieri, are yel­low­ish brown, sil­ver, or brass in col­oration with round spots evenly dis­trib­uted over the body. La­hon­tan cut­throat trout, O. c. hen­shawi, are dull in col­oration with large round spots evenly dis­trib­uted over the en­tire body. Paiute cut­throat trout, O. c. se­leniris, closely re­sem­ble the La­hon­tan cut­throat with a dull col­oration, but un­like the La­hon­tan, Paiute cut­throat lack spots. Bon­neville cut­throat trout, O. c. utah, have the same col­oration and spot­ting as Yel­low­stone cut­throat with one ex­cep­tion, the spots are larger on Bon­neville cut­throat. Col­orado river cut­throat trout, O. c. pleu­riti­cus, are strong red in col­oration along the lat­eral line and their lower sides are col­ored yel­low. They have spots but they vary by in­di­vid­ual. Green­back cut­throat trout, O. c. sto­mias, are sim­i­lar to Col­orado River cut­throat in col­oration, how­ever green­back cut­throat trout have larger spots. Rio Grande cut­throat trout, O. c. vir­ginalis, are sim­i­lar to green­back cut­throat in both col­oration and spot­ting. Rio Grande cut­throat have, in ad­di­tion, close spot­ting on the cau­dal pe­dun­cle. Yel­lowfin cut­throat trout, O. c. mac­donaldi, have the col­oration of the green­back but have a sil­very tint and their spots are ir­reg­u­lar. (Trot­ter, 1987; Willers, 1991; Behnke, 1992; Trot­ter, 1987; Willers, 1991)

The sub­species all share the fol­low­ing char­ac­ter­is­tics: red slash marks just below their gill cov­ers on the lower jaws (Trot­ter, 1987) and a scale count above the lat­eral line of more than 150 (Willers, 1991). Where cut­throat and rain­bow trout ranges over­lap, the two species can be dis­tin­guished by the pres­ence of ba­si­branchial teeth, or teeth on the base of the tongue (Trot­ter, 1987). Cut­throat trout posses them, while rain­bow trout do not. (Trot­ter, 1987; Willers, 1991)

The av­er­age length for a cut­throat trout is be­tween 20 and 40 cm while the av­er­age weight is be­tween 2 and 4 kg. Sur­pris­ingly, the en­vi­ron­ment a cut­throat trout oc­cu­pies may be the lim­it­ing fac­tor on how big a cut­throat can get, with ge­netic con­trol only being a fac­tor in an op­ti­mal en­vi­ron­ment (Behnke, 1993). (Behnke, 1992; Behnke, 1992)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry
• polymorphic

• Sexual Dimorphism
• sexes alike

• Range mass

  19 (high) kg

  41.85 (high) lb

• Average mass

  2-4 kg

  lb

• Range length

  99 (high) cm

  38.98 (high) in

• Average length

  20-40 cm

  in

De­vel­op­ment

Young cut­throat trout emerge from their eggs after two months (El­liot, 2005). Once they hatch they ma­ture, spawn, then die. Cut­throat trout that mi­grate to the sea de­velop for up to four years in their natal stream, then mi­grate into the ocean only to re­turn 2 to 3 months later to spawn (Behnke, 1992). (Behnke, 1992; El­liott, 2005)

• Development - Life Cycle
• indeterminate growth

Re­pro­duc­tion

On­corhynchus clarkii are stream spawn­ers like other fishes be­long­ing to the Salmonidae fam­ily (Vin­yard, 2004). Dur­ing a spawn­ing event a fe­male will dig a redd, a nest in gravel (Vin­yard, 2004). Males court fe­males by nudg­ing them with their noses and quiv­er­ing (El­liott, 2005). The fe­male lays her eggs in the redd and the male swims over and de­posits his sperm. (El­liott, 2005; Vin­yard, 2004; Willers, 1991)

• Mating System
• polygynous

Sea run cut­throat trout mi­grate from their ma­rine en­vi­ron­ments to their natal streams to spawn from Feb­ru­ary to early June (El­liott, 2005). Like­wise fresh­wa­ter cut­throat mi­grate from larger rivers and lakes to smaller streams to spawn (Behnke, 1992). Fe­males and males reach sex­ual ma­tu­rity at around 6 years of age. Both river and sea run cut­throat can spawn sev­eral times; how­ever, the prob­a­bil­ity of dieing dur­ing a spawn­ing event in­creases with age (Behnke, 1992). A sin­gle spawn­ing event pro­duces 1000-2000 eggs, which, if fer­til­ized, hatch just after 2 months of ges­ta­tion (El­liott, 2005). (Behnke, 1992; El­liott, 2005; Willers, 1991)

• Key Reproductive Features
• semelparous
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • external
• broadcast (group) spawning

• Breeding interval

  Breeding can occur once or twice in the lifetime of a cutthroat trout.

• Breeding season

  Spawning occurs from spring to early summer.

• Range number of offspring

  1000 to 2000

• Range time to hatching

  1 to 2 months

• Range age at sexual or reproductive maturity (female)

  5 to 7 years

• Range age at sexual or reproductive maturity (male)

  5 to 7 years

Prior to fer­til­iza­tionm fe­male cut­throat trout dig a redd, a nest in gravel (Vin­yard, 2004). Once eggs are de­posited and be­come fer­til­ized, the fe­male cov­ers them and may de­fend the redd for some time (Vin­yard, 2004). After a short pe­riod of guard­ing, the fe­male de­parts, leav­ing the eggs to hatch on their own. Once hatched, the par­ent cut­throat shows no type of parental in­vest­ment. (Vin­yard, 2004; Vin­yard, 2004)

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • protecting
    • female

Lifes­pan/Longevity

Cut­throat trout are not an ex­cep­tion­ally long lived fish. De­pend­ing on the sub­species a ma­ture trout may live any­where from 6-8 years (Behnke, 1992). (Behnke, 1992)

• Typical lifespan
  Status: wild

  6 to 8 years

Be­hav­ior

Cut­throat trout are soli­tary and seden­tary, rarely mov­ing or in­ter­act­ing un­less it is to ac­quire food or to mate. When they do move, they pro­pel them­selves through the water by mov­ing the lat­ter half of their bod­ies (sub­carangi­forms). Some pop­u­la­tions mi­grate from their natal streams to the ocean, while oth­ers mi­grate to lakes and ponds. (Behnke, 1992)

• Key Behaviors
• natatorial
• motile
• migratory
• sedentary
• solitary
• territorial

Home Range

Ju­ve­nile cut­throat es­tab­lish their home ranges when they are about two years old (Behnke, 1992). These home ranges are rel­a­tively small. Sea run cut­throat rarely travel more than 60 km from their natal streams (Behnke, 1992). (Behnke, 1992)

Com­mu­ni­ca­tion and Per­cep­tion

Cut­throat trout are vi­sual preda­tors. They de­pend on a keen sense of sight to lo­cate and con­sume their prey. Male cut­throat trout use body sig­nals when try­ing to court fe­males for spawn­ing (El­liott, 2005). It has been demon­strated that trout use chem­i­cal cues to re-lo­cate natal streams for spawn­ing. (El­liott, 2005)

• Communication Channels
• tactile

• Perception Channels
• visual
• tactile
• chemical

Food Habits

A cut­throat trout's diet changes as they progress through the life stages. As fry they feed on small crus­taceans and algae. As they progress into fin­ger­lings they feed on small in­sects, and crus­taceans. Ju­ve­niles and adults be­come op­por­tunis­tic feed­ers, eat­ing al­most any prey item in their en­vi­ron­ment (Behnke, 1992). They are known to eat other fishes, crus­taceans, and in­sects (Mor­row, 1980). (Behnke, 1992; Mor­row, 1980)

• Primary Diet
• carnivore
  • piscivore
  • insectivore
  • eats non-insect arthropods

• Animal Foods
• amphibians
• fish
• eggs
• insects
• terrestrial non-insect arthropods
• mollusks
• terrestrial worms
• aquatic or marine worms

• Plant Foods
• algae

Pre­da­tion

Young cut­throat trout are preyed on by larger fish and large, wad­ing birds. Adult trout are preyed on by large preda­tors, such as bears. There are sev­eral life his­tory adap­ta­tions they posses that in­creases their chances of sur­vival. Cut­throat often se­lect spawn­ing grounds that are iso­lated from spawn­ing grounds used by other fish (El­liott, 2005). Ju­ve­niles are also sit and wait preda­tors dart­ing out to cap­ture food, min­i­miz­ing the time dur­ing feed­ing that they are sus­cep­ti­ble to pre­da­tion (El­liott, 2005). Fry and fin­ger­ling cut­throat have par­marks on their sides, which cam­ou­flage them from pos­si­ble preda­tors (Behnke, 1992). (Behnke, 1992; El­liott, 2005)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • steelhead or rainbow trout (Oncorhynchus mykiss)
  • coho salmon (Oncorhynchus kisutch)
  • herons (Ardea)
  • bears (Ursus)

Ecosys­tem Roles

Cut­throat trout are prey for larger fish as fry or fin­ger­lings. As adults they be­come preda­tors. When sea run cut­throat die in their natal streams, they re­lease nu­tri­ents they ac­quired in the ocean as they de­com­pose. (El­liott, 2005; Mor­row, 1980)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Cut­throat trout are an im­por­tant sport fish through­out north­west­ern North Amer­ica (Trot­ter, 1987; Coad, 1995). They are also in­dica­tive of healthy ecosys­tems. (Coad, 1995; Trot­ter, 1987)

• Positive Impacts
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no neg­a­tive im­pacts of cut­throat trout on hu­mans.

Con­ser­va­tion Sta­tus

Cur­rently, cut­throat trout are not on the IUCN red list. There are some fac­tors that may put these fish on the list soon. Through stock­ing streams, rivers, and ponds with rain­bow trout through­out the west we may be putting na­tive cut­throat trout in harms way. Cut­throat trout and rain­bow trout read­ily mate, cre­at­ing hy­brids that are them­selves able to mate (Behnke, 1992). Cut­throat trout are also poor com­peti­tors, out-com­peted by all other trout species (Trot­ter, 1987). If we con­tinue to in­tro­duce non-na­tive trout to cut­throat streams and rivers, cut­throat trout may be elim­i­nated. An­other fac­tor af­fect­ing cut­throat trout is habi­tat loss. Log­ging and ex­ces­sive agri­cul­ture cause sed­i­men­ta­tion in trout streams, mak­ing them in­hab­it­able and un­suit­able for re­pro­duc­tion (Behnke, 1992). Three sub­species of On­corhynchus clarkii are threat­ened through­out the west­ern states. (Behnke, 1992; Trot­ter, 1987)

• IUCN Red List

  Data Deficient

• US Federal List

  Threatened

• CITES

  No special status

Con­trib­u­tors

Tanya Dewey (ed­i­tor), An­i­mal Di­ver­sity Web.

Lucas Spaete (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Kevin Wehrly (ed­i­tor, in­struc­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Behnke, R. 1992. Na­tiver Trout of West­ern North Amer­ica. Bethesda Mary­land: Amer­i­can Fish­eries So­ci­ety.

Coad, B. 1995. En­cy­clo­pe­dia of Cana­dian fishes. Sin­ga­pore: Cana­dian Mu­seum of Na­ture and Cana­dian Sport­fish­ing Pro­duc­tions Inc.

El­liott, S. 2005. "Alaska De­part­ment of Fish & Game" (On-line). Ac­cessed Oc­to­ber 17, 2005 at http://​www.​adfg.​state.​ak.​us/​pubs/​notebook/​fish/​c%5Etrout.​php.

Mor­row, J. 1980. The Fresh­wa­ter Fishes of Alaska. An­i­mal Re­sources Ecol­ogy Li­brary: Uni­ver­sity of B.C..

Trot­ter, P. 1987. Cut­throat. Boul­der Col­orado: Col­orado As­so­ci­ated Uni­ver­sity Press.

Vin­yard, G. 2004. "On­corhynchus clarkii hen­shawi" (On-line). Ac­cessed Oc­to­ber 16, 2005 at http://​www.​utexas.​edu/​tmm/​sponsored_​sites/​dfc/​na/​salmonid/​oncorhyn/​ochensha/​ochensha.​html.

Willers, B. 1991. Trout Bi­ol­ogy. New York New York: Lyons & Bur­ford.