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Biological Report 82(11.48) April 1986
Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Pacific Northwest)
COHO SALMON
Coastal Ecology Group Fish and Wildlife Service _____________ Waterways Experiment Station
U.S. Department of the Interior U.S. Army Corps of Engineers
Biological Report 82(11.48)TR EL-82-4April 1986
Species Profiles: Life Histories and Environmental Requirementsof Coastal Fishes and Invertebrates (Pacific Northwest)
COHO SALMON
Jeffrey C. Laufle, Gilbert B. Pauley, and Michael F. ShepardWashington Cooperative Fishery Research Unit
Colleqe of Ocean and Fishery SciencesUniversity of Washinqton
Seattle, WA 98195
Project OfficerJohn Parsons
National Coastal Ecosystems TeamU.S. Fish and Wildlife Service
1010 Gause BoulevardSlidell, LA 70458
Performed forCoastal Ecology Group
Waterways Experiment StationU.S. Army Corps of Engineers
Vicksburg, MS 39180
and
National Coastal Ecosystems TeamDivision of Biological Services
Research and DevelopmentFish and Wildlife Service
U.S. Department of the InteriorWashington, DC 20240
This series should be referenced as follows:
U.S. Fish and Wildlife Service. 1983-19 Species profiles: life historiesand environmental requirements of coastal fishes and invertebrates. U.S. FishWildl. Serv. Biol. Rep. 82(11). U.S. Army Corps of Engineers, TR EL-82-4.
Laufle, J.C., G.B. Pauley, and M.F. Shepard. 1986. Species profiles: lifehistories and environmental requirements of coastal fishes and invertebrates(Pacific Northwest)--coho salmon. U.S. Fish Wildl. Serv. Biol. Rep. 82(11.48).U.S. Army Corps of Engineers, TR EL-82-4. 18 pp.
PREFACE
This species profile is one of a series on coastal aquatic organisms,principally fish, of sport, commercial, or ecological importance. The profilesare designed to provide coastal managers, engineers, and biologists with a briefcomprehensive sketch of the biological characteristics and environmental require-ments of the species and to describe how populations of the species may beexpected to react to environmental changes caused by coastal development. Eachprofile has sections on taxonany, life history, ecological role, environmentalrequirements, and economic importance, if applicable. A three-ring binder isused for this series so that new profiles can be added as they are prepared. Thisproject is jointly planned and financed by the U.S. Army Corps of Engineers andthe U.S. Fish and Wildlife Service.
Suggestions or questions regarding this report should be directed to oneof the following addresses.
Information Transfer SpecialistNational Coastal Ecosystems TeamU.S. Fish and Wildlife ServiceNASA-Slide11 Computer Complex1010 Gause BoulevardSlidell, LA 70458
or
U.S. Army Engineer Waterways Experiment StationAttention: WESER-CPost Office Box 631Vicksburg, MS 39180
iii
Multiply B y To Obtain
mill imeters (mm)centimeters (cm)meters (m)kilometers (km)
0.03937 Inches0.3937 inches3.281 feet0.6214 miles
square meters (m2)square kilometers (km2)hectares (ha)
10.76 square feet0.38612.471
square milesacres
liters (1)cubic meters (m3)cubic meters
0.2642 gallons35.31 cubic feet0.0008110 acre-feet
milligrams (mg) 0.00003527 ouncesgrams (g) 0.03527 ounceskilograms (k
9) 2.205
metric tons t)pounds
2205.0 poundsmetric tons 1.102 short tonskilocalories (kcal) 3.968 British thermal units
Celsius degrees 1.8(OC) + 32 Fahrenheit degrees
inches 25.40 millimetersinches 2.54 centimeters
feet (ft) 0.3048 metersfathoms 1.829 metersmiles (mi) 1.609 kilometersnautical miles (mi) 1.852 kilometers
square feet (ft2)acressquare miles (mi2)
0.0929 square meters0.4047 hectares2.590 square kilometers
gallons (gal) 3.785cubic feet (ft3) 0.02831acre-feet 1233.0
literscubic meterscubic meters
ounces (oz) 28.35pounds (lb) 0.4536short tons (ton) 0.9072British thermal units (Btu) 0.2520
Fahrenheit degrees 0.5556("F - 32)
iv
gramskilogramsmetric tonskilocalories
Celsius degrees
CONVERSION TABLE
Metric to U.S. Customary
U.S. Customary to Metric
****************************************CONTENTS************************************
PREFACE
CONVERSION TABLE
ACKNOWLEDGMENTS
NOMENCLATURE/TAXONOMY/RANGE
MORPHOLOGY/IDENTIFICATION AIDS
REASON FOR INCLUSION IN SERIES
LIFE HISTORY
Spawning And Eggs
Larvae, Fry, And Smolts
Ocean Life
Survival
GROWTH CHARACTERISTICS
THE FISHERY
ECOLOGICAL ROLE
ENVIRONMENTAL REQUIREMENTS
Temperature
Water Depth
Water Velocity
Oxygen
Space
Other Factors
LITERATURE CITED
ACKNOWLEDGMENTS
We gratefully acknowledge the reviews by Sam Wright, Washington Departmentof Game, Olymoia, and Gary Thomas, School of Fisheries, University ofWashington, Seattle.
vi
Figure 1. Coho salmon adults, with spawning phase of male at bottom (from Scottand Crossman 1973).
COHO SALMON
NOMENCLATURE/TAXONOMY/RANGE
Scientific name . . . . . Oncorhynchuskisutch (Walbaum)
Preferred common name Coho salmon(Figure 1)
Other common names Silver salmon,silver trout (in freshwater), coho,sea trout, blueback, hooknose (Hawand Buckley 1973; Scott andCrossman 1973)
Class . . . . . . . . .. . OsteichthyesOrder . . . . . . . . . SalmoniformesFamily . . . . . . . . . . Salmonidae
Geographic range: Anadromous in northPacific Ocean, and coastal areafrom Monterey, California, northto Point Hope, Alaska, throughthe Aleutians, and from theAnadyr River, U.S.S.R., south to
Korea and Hokkaido, Japan. Mostabundant between southern Oregonand southeast Alaska. Coho havebeen planted successfully inlakes and reservoirs in Alaska,Washington, Oregon, Californiaand in some cases in Montana formany years. The first success-ful stocking in the Great Lakeswas in 1966, with a continuedsport fishery since then. Otherplantings include AtlanticStates from Maine to Maryland(moderate success) plus Argentinaand Chile (some success in Chile)and Alberta, Canada (apparentlysuccessful: Scott and Crossman1973). Major spawning rivers andareas of concentration for thePacific Northwest United Statesare shown in Figure 2, and
1
QuillayutelR.%.IS_-- ” ”
OREGON
CALIFORNIA . --+ -_ - _s
Figure 2. Major Pacific Northwest spawning rivers of coho salmon. Coho arefound in all marine waters of the area (Scott and Crossman 1973).
2
saltwater migration patterns ofadult coho salmon as determinedfrom tagged and marked hatcherysmolts are shown in Figure 3.Juveniles can migrate tosoutheast Alaska and farther inthe first few months at sea.
MORPHOLOGY/IDENTIFICATION AIDS
Dorsal fin 9-12 rays; adiposepresent; anal fin 12-17 rays; pectoralfin 13-16 rays; ventral fin 9-11 rayswith axillary process; lateral linescales 121-148; pyloric caeca 45-83;vertebrae 61-69; gill rakers 18-26 onfirst gill arch; branchiostegal rays11-15. Measurements as percent: bodydepth 24 (in standard length); headlength 22 (in total lenqth); headlonger in spawning males (Hart 1973).
Body fusiform, somewhat com-pressed laterally; fork length usual-ly 46 to 61 cm, maximum 98 cm; and3.6 to 4.5 kg, with a maximum of 14kg in marine populations (Scott andCrossman 1973).
Pigmentation: Juveniles coloredblue-green dorsally, with silverysides, and 8 to 12 widely spaced, nar-row parr marks; lateral line throughcenter of marks; dark adipose fin;oranqe caudal fin; and large orangeanal fin with three lonq white anteri-or rays and black posteriorly. Ocean-dwelling adults steel-blue to greenishdorsally; silvery sides, and whiteventral surface; small black spots onback, upper sides, dorsal fin base,and upper lobe of caudal fin. Beforespawning, males acquire darker, duskyblue-green back, with bright redstripe on dull sides, grey to blackventral surface.
Pale gums in marine adult cohodistinguish it from chinook salmon(Oncorhynchus tshawytscha), which haveblack qums. Spotting confined to up-per lobe of caudal fin (spotting onboth lobes in chinook), and number ofpyloric caeca less than 83 in coho and
greater than 140 in chinook, accordingto Dahlberg and Phinney (1967). Juve-nile coho have piqmentation overentire adipose fin, while juvenilechinook have an unpigmented adipose(Dahlberg and Phinney 1967).
REASON FOR INCLUSION IN SERIES
Coho salmon constitute a valu-able part of the commercial and sportfisheries of the west coast freshwaterand marine environments. They arethe object of extensive hatchery rear-ing and release programs. They aretertiary carnivores, and are them-selves preyed upon.
LIFE HISTORY
Spawning and Eggs
Coho are anadromous, enteringfreshwater to spawn (Godfrey 1965).Beginning in July, but later thanAugust in some areas such as GraysHarbor, they return from the openocean to coastal areas near theoutlets of their natal streams. Theyenter rivers on all but peak floods,moving upstream primarily in daylight.Runs take place from August to Febru-ary. Eames and Hino (1981) reported aNovember peak in a Washington stream.
Coho salmon spend 30 to 60 daysin freshwater, and in North America,peak spawning occurs from late Septem-ber to January, and continues as lateas March. The fish usually spawn insmall streams, but also use largemain streams, thouph seldom more than240 km above the mouth. They spawnin relatively fast water (0.3 to 0.5m/sec vs. 0.1 m/sec for sockeye), nor-mally in riffles or where ground seep-age occurs. Although numbers of malesand females in a spawninq run are sim-ilar males may predominate early inthe run and females later. More malesare present overall due to jacks (sex-ually precocious males that returnearly), while females predominate
3
P A C I F I C O C E A N
h9 British C o l u m b i a f i s h
I3Washington f ish
C o l u m b i a River fish
c l Oregon fish
la C a l i f o r n i a f i r h
Scale in Mi les
0 100 2 0 0
OREGONoos BAY
I4 PORT ORFORD
'igure 3. Oceanic migration patterns of adult coho salmon on the west,
coast of British Columbia, Washington, Oregon and northern California, asdetermined from tagged and marked hatchery smolts (Wright 1968).
4
slightly in the older adults. Morethan one male often competes for aspawning female. Spawning takesplace at temperatures of 0.8O to7.7O C Kamchatka(Gribanov G48) and at 4:4O
U.S.S.R.to 9.4O c
on the west coast of the United States(Reiser and Bjornn 1979).
Fecundity of coho salmon is vari-able depending on the size of the fe-male, geographic area, and year. Scottand Crossman (1973) cited a range ofabout 1,440 to 5,700 eggs for females44 to 72 cm long in Washington, andan average of 2,100 to 2,789 eggs perfemale (no lengths given) in BritishColumbia. Estimates in Kamchatka putcoho salmon second to chinook salmonin fecundity, but no lengths were giv-en. Shapovalov and Taft (1954) devel-oped the following fecundity formula:number of eggs = 0.0115: sX403fork
length l
The female may deposit eggs inthree or four redds (nests), whichshe digs by lying on her side andbeating out the gravel with hertail. A dominant male moves in andjoins the female; the spawningact consists of vibration by bothfish, with gapimg mouths, andthe release of eggs and milt. Theeggs are covered with gravel displacedfrom the uostream side of the nest.Eggs are demersal, large (about 4.5to 6.0 mm), and red. The femaleguards the nest for a short time, butboth parents die soon after spawning(Scott and Crossman 1973). Incuba-tion time apparently varies inverselywith temperature, as shown by thefollowing observations:
38 days at 11" C averaqe48 days at 9" C averaqe86-101 days at 4.5' C.
Larvae, Fry, and Smolts.
Newly hatched larvae possess alarge yolk sac, which they absorbwhile remaining in the gravel for 2to 3 weeks following hatching. Theyare at first photonegative, but become
photopositive, and face upcurrent aswell. Newly emerged fry have beenobserved from March to July. The frylive in shallow qravel areas, at firstschooling; after a short time the.ydisperse up- and downstream. Optimumrearing habitat for coho consists ofa mixture of pools and riffles, abun-dant instream and b a n k cover, watertemperatures that average between looand 15O C in the summer, dissolvedoxygen near saturation, and lowamounts of fine sediments (Reiser andBjornn 1979).
Small numbers of coho salmon maymiqrate to sea,residence
but at least a year'sin freshwater is normal.
However, there is a gradation from 1year in freshwater in Washinqton upto 2 years in freshwater in centralBritish Columbia, with more northerlyfish usually spending 2 years infreshwater. For example, fish in theYukon River drainage spend 2 years infreshwater (Scott and Crossman 1973). As they grow, the fry move to deeperwater, feeding on progressively larg-er foods. In winter they feed andgrow little. The juveniles usuallymigrate downstream from April toAugust of the year followinq theirhatching, with peak migrations in Mayin nearly all areas. Nighttime migra-tion appears to be the rule (McDonald1960).
Size and age of the fish, as wellas stream conditions, trigger outmi-gration. The radical physiologicaland behavioral changes that occurduring smoltification make salmon inthis stage particularly sensitive toenvironmental stress factors. Forexamole, elevated water temperaturescan accelerate the onset of smoltifi-cation and shorten the smoltingperiod, sometimes resulting in seawardmigration of smolts at a time whenconditions are unfavorable (Wedemeyeret al. 1980). Larger juveniles arebelieved to be the first to godownstream, but aggression by largerfry may induce early downstreammovement by smaller ones soon after
emergence (Chapman 1962; Mason andChapman 1965).
Ocean Life
Early studies indicated that cohosalmon did not migrate far offshore,but more recent hiqh-seas research hasshown differently. They have beencaptured as far as 1,930 km away fromtheir point of origin on the NorthAmerican west coast. Movement ofthese fish is not random, since markedadult fish from the Columbia River arerare in Alaska salmon catches. TheNorth American west coast oceanic mi-gration patterns of adult coho salmon,as determined from taqqed and markedhatchery fish, are depicted in Figure3. Offshore miqrations by juvenilescommence in July and August, as evi-denced by sharp declines in inshorecatches of juveniles at that time.There are two migration types of cohosalmon in Washington and British Co-lumbia: "ocean," or high-seas dwell-ers, migrate great distances, while"inshore" fish such as those livingas residents in the Strait of Georgiaor Puget Sound migrate very littleand stay near their river of origin.Four types of life histories occur inthe Puget Sound-Georgia Strait area:(1) ocean migrants that go to sea inthe sprinq of the second year; (2)resident fish that go to the ocean inthe fall of the second year afterspendinq the summer in inside marinewaters; (3) resident fish that go tothe ocean in the spring of their thirdyear after 1 year in inside marinewaters; and (4) true residents thatspend their entire lives in the insidemarine waters. Each of these groupsis proqressively smaller in averagesize, due to less time in the openocean. High-seas fish of NorthAmerican origin probably winter southof 45O N. lat., and move north inmid- to late summer, later than doother salmon.
Coho salmon apparently concen-trate in the Gulf of Alaska in thesummer, dispersing coastward from
there. Milne (1950) indicated thatmigrations are mostly direct ratherthan alongshore. Fish reportedlymove slowly, wandering as they mi-grate, although they have averaged upto 30 mi per day over long distances.The delays are attributed to inten-sive feeding until late in theirjourney.
Most coho salmon, including juve-niles and adults, are found within 10m of the sea surface except when cov-ered by a shallow layer of warmer"tuna" water. This zone is where thesport fishery concentrates its efforts(Haw and Buckley 1973).
As a rule, adult coho salmonspend two growing seasons at sea, ap-pearing offshore near the outlets oftheir rivers of oriqin in the secondsummer after they enter saltwater. Insoutheast Alaska and northern BritishColumbia, they arrive in large numbersin July, and in southern British Co-lumbia, Washington, and Oregon theirarrival is later, with a general tim-ing gradation that is progressivelylater the more southerly the run.They home almost entirely to thestreams of their origins, and thesmall percentages that do stray mi-grate primarily to nearby streams.
Survival
Various studies (Salo and Bayliff1958; Tagart 1976) were used by theWashington Department of Fisheries (inpress) to derive a composite lifesequence to predict average smoltproduction per female coho salmon.From this, an average production of 75smolts/female was estimated. This isapplicable only to the 3-year-old fishthat spend 2 years at sea in thesouthern part of their range, south ofcentral British Columbia.
GROWTH CHARACTERISTICS
Most coho salmon reside in theocean for two growing seasons, return-
6
ing at the end of the second summer.These are designated aqe 32 or 4_3upon return for spawning (integer istotal age and the subscript is year oflife at outmigration). Those thatspend 1 year in freshwater would be3 2, while those that spend 2 years infreshwater before outmigrating wouldbe age 4,. The precocious males("jacks") or females ("jills" or"jennies") that return to spawn afteronly one summer are designated as 2,.
California coho salmon averaged16 cm at outmigration, and grew anaverage of about 52 cm while at sea(Shapovalov and Taft 1954). Kamchat-kan coho salmon were similar, withocean growth much faster than fresh-water growth for both 3, and 43 fish(Gribanov 1948). The Kamchatkan re-turnees averaged 60 cm FL (range 40-87 cm), and 3.5 kg (range 1.5 - 6.5kg). Males were larger than females.The California returnees' sex, age,and average fork length were asfollows: 22 males, 46 cm FL; 32males, 64.7 cm; 3, females, 63.9 cm.Males were typically larger thanfemales.
THE FISHERY
Coho salmon are a highly valuedspecies, the object of large commer-cial (Table 1) and sport (Table 2)fisheries. Additional data demon-strate the value of coho salmon inU.S. commercial fisheries: in 1980,39.3 million pounds, worth $43.1million, were landed; in 1981, 35.2million pounds were landed, at $33.3million (U.S. Department of Commerce1982). Most commercial landings areclose to shore (29.7 million poundsfrom 0 to 4.8 km out, versus 5.5 mil-lion pounds from 4.8 to 322.0 km out,in 1981). Coho ranked consistentlyfourth behind sockeye salmon (Oncorhynchus nerka), oink salmon (O.gorbuscha), and chum salmon (0. keta),in the Pacific coast commercial fish-ery from 1968 to 1978, and made up 8%to 11% of the total catch (Interna-tional North Pacific Fisheries Commis-
sion 1971-81). The Lake Michigan cohosalmon sport fishery is outproducingthe entire U.S. Pacific Coast cohosalmon sport fishery (Tanner 1974).
Coho salmon are fished commer-cially with gill nets, set nets(treaty Indians only, in Washington),purse seines, and trolling gear(Washington Department of Fisheries etal. 1973). Sport fishing is by hookand line in saltwater and in streams.Saltwater angling is both off-coastand inshore, with Puget Sound, forexample, supporting a substantialfishery in late summer for ocean andresident fish. Haw and Buckley (1973)discussed sport fishing techniques indetail. Salo (1974) estimates thatanglers spent between $100 and $125 in1966 to catch a coho salmon.
Many coho salmon are reared andreleased from State, Federal, andother hatcheries; about 40% to 50% ofthe net-caught salmon in Puget Soundare estimated to be of hatchery ori-gin. Coho salmon and chinook salmonare the most successfully reared sal-monid species. Hatcheries have becomeimportant because of such developmentsas pellet-sized food, better diseasetreatment, and the rearing of fish tothe yearling stage (Fulton 1970). Co-lumbia River runs have been enhancedby hatcheries since 1959.
Current management objectives ofthe Washington Department of Fisheriesare toward maximum sustained harvest,with the treaty Indian Tribes underthe Boldt Decision (United States vs.State of Washington) having a legalright to 50% of the catchable alloca-tion. Preseason run sizes for eachindividual river are estimated andescapement goals for each river arepredicted (Zillges 1977; an escapementgoal is the number of spawnersnecessary to maintain the run of agiven size, and a goal may vary fromyear to year. In-season runreassessments are also made (Zillges1977). From these predictions andprojections each year, the catchable
7
Table 1. Annual canmercial landings of coho salmon by State or Province inmetric tons (MT) and number of fish (in thousands) for the years 1968-78. Datafrom International North Pacific Fisheries Commission (1971-81).
British Columbia Al aska Washington OregonYear M T Fish MT Fish MT Fish MT F i s h
1968 15,100 5,257 9,530 2,751 3,950 1,275 2,620 9291969 7,990 2,414 3,660 1,133 3,220 920 2,240 8021970 13,649 3,946 5,407 1,527 7,885 1,870 5,935 1,4011971 14,089 4,788 5,208 1,447 6,100 2,002 5,341 1,6951972 10,536 3,359 6,415 1,831 4,471 1,253 2,941 9251973 11,227 3,531 4,948 1,457 5,854 1,672 3,314 9371974 10,379 3,724 6,394 1,862 6,923 2,117 4,562 1,3281975 7,736 2,332 3,233 1,014 6,389 1,837 2,641 7721976 9,325 3,698 5,063 1,432 5,530 2,162 5,096 1,9361977 9,856 3,341 6,987 1,815 5,536 1,745 1,493 4781978 19,152 3,350 9,062 2,821 4,222 1,480 1,870 730
Table 2. Estimated numbers of coho salmon caught in the recreational fisheriesof four States during 1970-78. Asterisk (*) indicates marine catches only.Data from International North Pacific Fisheries Commission (1971-81).
Year Alaska Washington Oregon California
1970 32,075 540,231* 279,602 14,615*1971 50, 500 845,735* 335,003 67,421*1972 37,510 615,895* 135,078 43,770*1973 42,575 552,255 254,610 31,641*1974 50,550 788,981 339,126 78,162*1975 70,300 701,721 273,892 20,860*1976 59,100 1,195,579 127,490 57,642*1977 104,090 683,108 212,371 26,788*1978 131,945 713,219 268,980 44,282*
t
allocation of coho salmon in eachindividual river is made withnon-Indians receiving 50% and treatyIndians receiving 50%. The non-Indianshare is then divided betweencommercial fishermen and sportanglers.
Management methods for coho andother salmon must include freshwaterhabitat assessment, stock assessmentincluding run size, habitat protec-tion and improvement, and artificialpropaqation. The Washington Depart-ment of Fisheries has been usinqSmoker's (1953) preseason method inPuget Sound to predict coho salmoncatches from stream discharge data,as well as the previous year's jackrun size. Such factors, however, asenvironmental extremes, saltwaterenvironmental variations, and fishingintensity also play a role (Zillqes1977). Other methods are beingdeveloped and used in other areas bycooperative effort between Statebiologists and tribal biologists.
Wright (1951) described the com-plexities of salmon management, stat-ing that good run forecasts with ac-curate and timely reassessments areimportant. Also, runs dependent uponhatcheries could be harvested at ahigher rate than wild runs because ofhigh survival of juveniles in hatcher-ies. Where two stocks coexist geo-graphically, maximum sustainable yieldshould be defined for the weakerstock, with the surplus fish takenwhere the stronger stock is easier totarqet. He argued against dependingon user groups, i.e., fishermen, forsound management;resource shouldcriterion used inprocedures.
ECOLOGICAL ROLE
the vitality of thebe the primary
designing management
Coho salmon fill different nichesin freshwater and in saltwater. Thealevins living in gravel do not feed,but depend on the yolk sac for nour-
9
ishment. Even though part of theyolk sac may remain after emergence,the fry begin to feed immediatelyafter emergence (Godfrey 1965).Johnson (1970) stated that juvenilesalmon in Washington, depending onthe season and stream, ate variouslife stages of aquatic insects (most-ly at the surface), such as dipterans,ephemeropterans, plecopterans andother insects, as well as crustaceansand fishes. If their normal food isscarce, juvenile coho will eat insectexuviae, though this provides no nu-trition (Mundie 1969). Alaskan cohofingerlings prey on sockeye salmonfry (Oncorhynchus t nerka); 30% ofcoho captured bet ween May and July hadsockeye remains in their stomachs(Roos 1960). They ate the sockeyeeven though sticklebacks were moreabundant.
Fresh et al. (1981) categorizedthe food of coho salmon by zones inPuget Sound and other Washington ma-rine waters. Juvenile fish from sub-littoral habitats had stomach contentsconsisting mainly of decapod crusta-cean larvae,. plus fishes (mostly herr-ing), amphipods, and polychaetes. Inthe nearshore pelagic zone, some juve-niles examined had brachyuran crablarvae as their primary food item.Young coho from the offshore pelagiczone ate euphausids, fishes (mainlyherring), gammarids, and decapod lar-vae. Fishes formed the hiahest bio-mass, but occurred in only 30% of thecoho salmon stomachs. Offshore inthe Pacific, near the Columbia River,young adult coho examined were largerthan those in Puget Sound and atemostly fishes, including anchovy, surfsmelt, whitebait smelt, herring,juvenile chinook, and juvenilerockfish. They also fed on euphausidsand crab larvae off Oregon andWashington (Silliman 1941; Heg and VanHynning 1951). In the Great Lakes,coho and other salmon have confirmedhopes that they would consume thesmelt and alewives present there inabundance (Scott and Crossman 1973).
Coho salmon themselves are theprey of a variety of animals. Cohojuveniles are taken by other fishes,including other coho salmon, trout,squawfish, and sculpins (Scott andCrossman 1973). Birds that prey uponcoho include merqansers, kingfishers,and loons. Spawning adults are eatenby animals such as bears and eagles.Seals and killer whales prey on ocean-dwelling salmon, while man and para-sitic lampreys prey on coho in marineand freshwater environments.
The predation by adult coho onjuvenile sockeye salmon, chinook sal-mon and coho salmon is indicative oftheir aggressiveness. Scott andCrossman (1973) stated that coho sal-mon also eat chum and pink salmon fry.Mason and Chapman (1965) indicatedthat coho fry are agqressive and ter-ritorial soon after emergence, andestablish intraspecific dominancehierarchies. Where coho and chinookfry occurred toqether in streams. thecohoingfoodtheweresame
were socially dominant, defend-territory accessible to incoming(Stein et al. 1972). Coho werefaster growing of the two, andheavier than chinook fry of thelength.
monProduction of juvenile coho sal-in three Oregon streams averaged
9 q/m’/yr over 4 years1965).
(ChapmanMeasurements were made over
14 months of stream residence time.Monthly averaqes were 1.9 to 2.8 g/m2following emergence,0.2-0.3 g/m*
dropping toby winter. Pearson et
al. (1970) found that coho productionper unit area was higher in pools withlarge riffles upstream than in poolsdownstream of small riffles, becauseof a greater available food supply.
Dill (1969) stated that fry ex-pand their territories at 1.5 to 2months. The reduction in density maybe a result of predation, which God-frey (1965) postulated may be a majorfactor in an observed decline in num-bers following the peak of emergence.
ENVIRONMENTAL REQUIREMENTS
Reiser and Bjornn (1979) reviewedthe habitat needs of coho in streamswhich are summarized in Table 3.McMahon (1883) has constructed aHabitat Suitability Index pertainingto riverine habitat for various lifestages of coho salmon.
Temperature
Preferred temperatures for cohosalmon in streams range between 11.8Oand 14.6'C (Bell 1973), and 25.8'C isthe upper lethal limit. As statedearlier, incubation time varies withtemperature. The shortest time givenby Godfrey (1965) was 38 days atll”C, and the longest was 86 to 101days with a temperature of 4.5OC.Godfrey (1965) listed 4.0' to 15.2OCas the oceanic temperature rangewhere coho salmon have been taken,with the best catches occurring be-tween 8' and 12OC. Streamside vege-tation plays an important role inregulating the stream temperatures.
Water Depth
Adult coho salmon can spawn inshallow water (0.18 m), but young fishapparently prefer deeper water (0.3-1.2 m), where most of the availableriffle area is submerged (Table 3).
Water Velocity
Adults can swim in water veloci-ties as high as 2.44 m/sec, with evenfaster bursts of speed, while adultspawning and juvenile rearing musttake place in water velocity of wellunder 1 m/sec (Table 3). Water velo-cities preferred by invertebrate fooditems are in the range of 0.15 to1.22 m/sec.
Oxygen
Coho salmon, especially embryosand juveniles, prefer highly oxygenat-
Table 3. Summary of preferred habitat requirements for coho salmon in streams(from Reiser and Bjornn 1979).
Habitat requirements Value
TemperatureAdult migration upstreamSpawningIncubationUpper lethalPreferred range
Water depthAdult migration upstream (minimum)Spawning (minimum)Age 0 fish (preferred)(60% of riffle should be submerged)
-ration upstream (maxmium)SpawningAqe 0 fish (preferred)Riffle velocity for rearingPool velocity for rearingAdult swimming speeds: cruising
sustaineddarting
Invertebrate food organisms
02Weiqht gain in fry stage
Food conversion (9 mg/l maximum tested)Juvenile swimming speed (maximum)Incubation
Space (area)Average size of reddRecommended area per spawninq pairYear l+ fish
SubstrateSpawning
Silt loads
7.2' - 15.6°C4.4O - 9.4OC4.4O - 13.3OC
25.8'C11.8' - 14.6OC
0.18 m0.18 m0.30 - 1.22 m
2.44 m/set0.31 m/set0.09 -CO.30 m/set0.31 - 0.46 m/set0.09 - 0.24 m/set0 - 1.04 m/set1.04 - 3.23 m/set3.23 - 6.55 m/set0.15 - 1.22 m/set
4 - 9 mg/l for 70% - 100% gainover 19 - 28 days4 - 9 mg/l100% saturationNear saturation (>5 mg/l)
2.8 m211.7 m22.4 - 5.5 m2 fish
20% fine sediment<6.4 mm in riffle substrate
<25 mg/l preferable
GtherGood overhead and submerged coverRiffle/pool ratio of 1:l
11
ed water. Growth and food conversiondecline at levels below about 4 mg/l.Swimming ability of juveniles also candrop in unsaturated water. Reducedoxygen levels inhibited growth andlengthened incubation time for cohoembryos (Shumway et al. 1964). Lowoxygen concentrations reduced surviv-al of coho embryos (Phillips andCampbell 1961).
Space
Spatial requirements for spawn-ing and rearing are known (Reiser andBjornn 1979). Space requirements forjuveniles increase as they grow andare probably food related (Chapman1966), though Chapman (1962) statedthat food was not involved in theintraspecific agqressiveness he foundin coho fry. Pearson et al. (1970)did find greater production in pools,a situation that would seem to miti-gate density-dependent factors in-volved in aggression.
Other Factors
A substrate (gravel) size rangeof 1.3 to 10.2 cm necessary forspawning was cited by Reiser andBjornn (1979). Dill (1969) found thatcoho salmon survival at emergence wasgreater in large gravel than in small,but their condition was poorer; heattributed the survival to greaterease of water penetration and thepoorer condition to less support forthe alevins.
Low siltation is important forsurvival of eggs and juveniles.Reiser and Bjornn (1979) listedsilt loads of less than 25 mg/las best. High water velocitiesreduce deposition of fine sediment,which should make up less than40% of the riffle substrate. Largeamounts of deposited silt restrictoxygen flow to eggs and fry, and trapfry attemptinq to leave the gravel(Lantz 1976). Sigler et al. (1984)reported that chronic turbidity af-
17
fected the emergence and rearing ofyoung coho salmon; a lower growth ratewas observed in fish subjected tocontinuous clay turbidities comparedto fish grown in clear water. Stoberet al. (1981) studied the reactionsof coho and chinook salmon to Mt. St.Helens, Washington, volcanic ash andmudflow sediment in two rivers. Infield livebox experiments theyobtained 96-h LC5
e!'s at 1,217 and 509
mg/l of suspend mud and ash forcoho presmolts and smolts, respect-ively. A comparative static bioassaywith ash produced 96-h LC 's at18,672 and 28,184 mg/l for pr smolts5&and smolts, respectively. A static96-h bioassay using mudflow sedimentsproduced mortality in smolts at 29,580m g / l Complete presmolt mortalityoccurred in the Cowlitz River in thesummer following the 18 May 1980 erup-tion (Stober et al. 1981). As pointedout by Reiser and Bjornn (1979), highlevels of suspended sediments can clogand abrade gills, curtail feeding, andcause avoidance of areas by fish.Sediment also may destroy food sup-plies (Cordone and Kelley 1961).
Salmon abundance has been linkedto available cover in a stream (Reiserand Bjornn 1979). Overhead cover pro-vides shade and protection from ter-restrial predators, while submergedcover provides shelter from currentand predators.
A list of examples of habitatalterations and how they adversely af-fect Salmonid populations was reportedby the Washington Department of Fish-eries et al. (1973). Logging, forinstance, causes sedimentation, ele-vated water temperatures from lack ofadequate cover, stream damming, decom-position of orqanics and high biologi-cal oxygen demand (BOO), and possiblesevere erosion and rapid runoff (espe-cially in clearcuts). Hall and Lantz(1969) cited daily stream temperaturefluctuations caused by logging opera-tions as serious threats to coho sal-mon. The Washington Department of
Fisheries et al. (1973) additionallylisted irriqation (removinq water,adding pollutants, entraininq juve-niles), damminq (migration delay orprevention, spawning habitat destruc-tion from reservoir coverage, turbine-and spillway-related mortalities,possible increased predation in res-ervoirs), industrial projects (waterconsumption, pollution), channeliza-tion (pool and riffle elimination,siltation), and residential develop-
ment (floodinq and erosion), asdetrimental to Salmonid habitat.Detailed summaries on several human-made structures and activities thatnegatively impact Salmonid habitathave been published: paper mills(Schmiege 1980), forest roads (Yee andRoelofs 1980). mining (Martin andPlatts 1981), livestock grazing(Platts 1981), logging (Chamberlin1982), and silviculture (Everest andHarr 1982).
13
LITERATURE CITED
Bell, M.C. 1973. Fisheries handbookof engineering requirements and bio-logical criteria. Useful factors inlife history of most common species.U.S. Army Corps of Engineers,Fish.-Eng. Res. Program, Portland,Oreg. (unpublished; cited in Reiserand Bjornn 1979).
Chamberlin, T.W. 1982. Timber har-vest. Pages l-30 in W.R. Meehan,ed. Influence of forest and range-land management on anadromous fishhabitat in western North America.U.S. For. Serv. Gen. Tech. Rep.PNW-136. Pacific Northwest Forestand Range Experiment Station,Portland, Oreg.
Chapman, D.W. 1962. Aggressive be-havior in juvenile coho salmon as acause of emiqration. J. Fish. Res.Board Can. 19(6): 1047-1080.
Chapman, D.W. 1965. Net productionof juvenile cohoOregon streams.Soc. 94(1): 40-52.
Chapman, D.W. 1966as requlators oftions in streams.345-357.
salmon in threeTrans. Am. Fish.
Food and spaceSalmonid popula-
Am. Nat. 100:
Cordone, A.J., and D.W. Kelley. 1961.The influence of inorganic sedimenton the aquatic life of streams.Calif. Fish Game 47(2): 189-228.
Dahlberg, M.L., and D.E. Phinney.1967. The use of adipose fin pig-mentation for distinguishing betweenjuvenile chinook and coho salmon inAlaska. J. Fish. Res. Board Can.24( 1) : 209-211.
Dill, L.M. 1969. The subgravel be-havior of Pacific salmon larvae.Pages 88-99 in T.G. Northcote, ed.Symposium on salmon and trout instreams. H.R. MacMillan Lecturesin Fisheries.British
University ofColumbia, Vancouver,
Canada.
Eames, M., and M. Hino. 1981. Amark-recapture study of an enumerat-ed coho spawning escapement. Wash.Dep. Fish. Prog. Rep. 148. 22 pp.
Everest, F.H., and R.D. Harr. 1982.Silvicultural treatments. Pages1-19 in W.R. Meehan, ed. Influenceof forest and rangeland managementon anadromous fish habitat inwestern North America. U.S. For.Serv. Gen. Tech. Rep. PNW-134.Pacific Northwest Forest and RangeExperiment Station, Portland, Oreg.
Fresh, K.L., R.D. Cardwell, and R.R.Koons. 1981. Food habits of Pacif-ic salmon, baitfish, and their po-tential competitors and predatorsin the marine waters of Washington,August 1978 to September 1979.Wash. Dep. Fish. Prog. Rep. 145.58 pp.
Fulton, L.A. 1970. Spawning areasand abundance of steelhead troutand coho, sockeye, and chum salmonin the Columbia River basin--pastand present. U.S. Natl. Mar. Fish.Serv. Spec. Sci. Rep. Fish. 618.37 pp.
Godfrey, H. 1965. Coho salmon. Int.North Pac. Fish. Comm. Bull. 16:l-39.
15
Gribanov, V.I. 1948. Coho (Oncorhyn-chus kisutch Walb.) (General Biolo-gy) Izvetstiia TINRO, Vol. 28.(Transl. from Russian by W.E.Ricker) Fish. Res. Board Can.Transl. Ser. No. 370.
Hall, J.D., and R.L. Lantz. 1969.Effects of logging on the habitatof coho salmon and cutthroat troutin coastal streams. Pages 355-375in T.G. Northcote, ed. Symposiumon salmon and trout in streams. H.R.MacMillan Lectures in Fisheries.University of British Columbia,Vancouver, Canada.
Hart, J.L. 1973. Pacific fishes ofCanada. Fish. Res. Board Can.Bull. 180. 740 pp.
Haw, F., and R.M. Buckley. 1973.Saltwater fishing in Washington.Stan Jones Publishing, Inc.,Seattle, Wash. 198 pp.
Heg, R., and J. Van Hynning. 1951.Silver salmon taken off the OregonCoast. Oreg. Fish. Comm. Res.Briefs 3(2):32-40.
International North Pacific FisheriesCommission. 1971-81. Statisticalyearbooks 1968-79. Vancouver,Canada.
Johnson, J.M. 1970. Food and feedinghabits of juvenile coho salmon andsteelhead trout in Worthy Creek,Washington. M.S. Thesis. Univers-ity of Washington, Seattle. 77 pp.
Lantz, R.L. 1976. Protection of sal-mon and trout streams in loggingoperations. Pages 14-20 in A.R.Grove, ed. Stream management ofsalmonids. Trout 17(1): wintersupplement.
Martin, S.B., and W.S. Platts. 1981.Effects of mining. Pages 1-15 inW.R. Meehan, ed. Influence of for-est and rangeland management onanadromous fish habitat in western
North America. U.S. For. Serv.Gen. Tech. Rep. PNW-119. PacificNorthwest Forest and Range Experi-ment Station, Portland, Oreg.
Mason, J.C., and D.W. Chapman. 1965.Significance of early emergence,environmental rearing capacity, andbehavioral ecology of juvenile cohosalmon in stream channels. J. Fish.Res. Board Can. 22(1): 172-190.
McDonald, J. 1960. The behavior ofPacific salmon fry during theirdownstream migration to freshwaterand saltwater nursery areas. J.Fish. Res. Board Can. 17(5):655-676.
McMahon, T.E. 1983. Habitat suita-bility index models: Coho salmon.U.S. Fish Wildl. Serv. FWS/OBS-82/10.49. 29 pp.
Milne, D. 1950. The difference inthe growth of coho salmon on theeast and west coasts of VancouverIsland in 1950. Fish. Res. BoardCan. Pac. Prog. Rep. 85:80-92.
Mundie, J.H. 1969. Ecological im-plications of the diet of juvenilecoho in streams. Pages 135-162 inT.G. Northcote, ed. Symposium onsalmon and trout in streams. H.R.MacMillan Lectures in Fisheries.University of British Columbia,Vancouver, Canada.
Pearson, L.S., K.R. Conover, and R.E.Sams. 1970. Factors affectingthe natural rearing of coho salmonduring the summer low flow season.Fish. Comm. Oreg., Portland (unpub-lished; cited in Reiser and Bjornn1979).
Phillips, R.W., and H.J. Campbell.1961. The embryonic survival ofcoho salmon and steelhead trout asinfluenced by some environmentalconditions in gravel beds. Pac.Mar. Fish. Comm. Annu. Rep.14:60-73.
16
Platts, W.S. 1981. Effects of livestock grazing. Pages l-25 in W.R.Meehan, ed. Influence of forest andrangeland management on anadromousfish habitat in western North Ameri-
U.S. For. Serv. Gen. Tech. Rep.zir-124. Pacific Northwest Forestand Range Experiment Station,Portland, Oreq.
Reiser, D.W., and T.C. Bjornn. 1979.Habitat requirements of anadromoussalmonids. Pages l-54 in W.R.Meehan, ed. Influence of forestand rangeland management on anadro-mous fish habitat in western NorthAmerica. U.S. For. Serv. Gen.Tech. Rep. PNW-96. Pacific North-west Forest and Range ExperimentStation, Portland, Oreg.
ROOS, J.F. 1960. Predation of youngcoho salmon on sockeye salmon fry atChignik, Alaska. Trans. Am. Fish.S o c 89(4): 377-379.
Salo, E.O. 1974. Anadromous fishes.Pages 12-21 in A.R. Grove, ed.Salmonid management. Trout 15(1):winter supplement.
Salo, E.O., and W.H. Bayliff. 1958.Artificial and natural reproductionof silver salmon, Oncorhyn chus ki-sutch, at Minter Creek, Washington ,Wash. Dep. Fish. Res. Bull: 4.75 pp.
Schmiege, D.C. 1980. Processingmills and camps. Paaes 1-17 in W.R.Meehan, ed. Influence of forestand rangeland management on anadro-mous fish habitat in western NorthAmerica. U.S. For. Serv. Gen.Tech. Rep. PNW-113. Pacific North-west Forest and Range ExperimentStation, Portland, Qreg.
Scott, Y.B., and E.J. Crossman. 1973.Freshwater fishes of Canada. Fish.Res. Board Can. Bull. 184. 966 pp.
Shapovalov, L., and A.C. Taft. 1954.The life histories of the steelheadrainbow trout (Salmo gairdneri
and silver salmon (Oncorhvnchus Oreg.sutch) with special reference ki-Waddell Creek, California, and re-commendation regarding their man-agement. Calif. Dep. Fish. GameFish. Bull. 98. 375 pp.
Shumway, D.L., C.E. Warren, and P.Duodoroff. 1964. Influence of oxy-gen concentration and water movementon the growth of steelhead trout andcoho salmon embryos. Trans. Am.Fish. Soc. 93(4): 342-356.
Sigler, J.W., T.C. Bjornn, and F.H.Everest. 1984. Effects of chronicturbidity on density and growth ofsteelheads and coho salmon. Trans.Am. Fish. Soc. 113(2): 142-151).
Silliman, R.P. 1941. Fluctuations indiet of the chinook and silver sal-mons (Oncorhynchus tshawytscha and0. kisutch) off Washington, asrelated to the troll catch of sal-mon. Copeia 1941(l): 80-87.
Smoker, W.A. 1953. Stream flow andsilver salmon production in westernWashington. Wash. Dep. Fish. Res.Pap. l(1): 5-12.
Stein, R.A., P.E. Reimers, and J.D.Hall. 1972. Social interactionsbetween juvenile c i i (Oncorh nchuskisutch) and fall chinookl l+iiz(O. tshawytscha) in Sixes River,Oregon. J fish. Res.29(12): 1737-1748.
Board Can.
Stober, Q.J., B.D. Ross, C.L. Melby,P.A. Dinnel, T.H. Jagielo, and E.O.Salo. 1981. Effects of suspendedvolcanic sediment on coho and chi-nook salmon in the Toutle andCowlitz Rivers. Univ. Wash. Fish.Res. Inst., Seattle. Tech. Compl.Rep. FRI-UW 8124. 161 pp.
Tagart, J.V. 1976. The survival fromegg deposition to emergence of cohosalmon in the Clearwater River,Jefferson County, Washington. M.S.Thesis. University of Washington,Seattle. 101 pp.
17
Tanner, H. 1974. Salmonids in lakes.Pages 22-31 in A.R. Grove, ed.Salmonid Management. Trout 15(1):Winter Supplement.
U.S. Department of Commerce, NationalMarine Fisheries Service. 1982.Fisheries of the United States,1981. U.S. Natl. Mar. Fish. Serv.Curr. Fish. Stat. No. 8200. 131 pp.
Washington Department of Fisheries.In press. Coho Salmon Workshop,Reston, Washington, October 13-14,1983. Proceedings.
Washington Department of Fisheries,U.S. Fish and Wildlife Service, andWashington Department of Game. 1973.Joint statement regardinq the biol-ogy, status, management, and harvestof the salmon and steelhead resourc-es of the Puqet Sound and OlympicPeninsula drainaqe in westernWashington. 140 pp.
Wedemeyer, G.A., R.L. Saunders, andW.C. Clarke. 1980. Environmentalfactors affecting smoltification andearly marine survival of anadromoussalmonids. Mar. Fish. Rev. 42(1):1-14.
Wright, S.G. 1968. Origin and migra-tion of Washington's chinook andcoho salmon. Wash. Dep. Fish. Inf.Booklet 1. 25 pp.
Wright, S.G. 1981. ContemporaryPacific salmon fisheries manage-ment.I(l):29-4::
Am. J. Fish. Manage.
Yee, C.S., and T.D. Roelofs. 1980.Planning forest roads to protectSalmonid habitat. Paqes l-26 inW.R. Meehan, ed. Influence offorest and ranaeland management onanadromous fish habitat in westernNorth America. U.S. For. Serv.Gen. Tech. Rep. PNW-109. PacificNorthwest Forest and Ranqe Experi-ment Station, Portland, Oreg.
Zillges, G. 1977. Methodology fordetermining Puget Sound coho escape-ment goals, escapement estimates,1977 pre-season run size predictionand in-season run assessment. Wash.Dep. Fish. Tech. Rep. No. 28. 65pp.
18
Ic::? ‘c:
REPORT DOCUMENTATION REPORT NO.PAGE Biol. Rep. 82(11.48)*
4. Title and Subtitle
Species profiles: life histories and environmental April 1986requirements of coastal fishes and invertebrates (PacificNorthwest)--Coho Salmon
7. Author(s)
Jeffrey C. Laufle, Gilbert B. Pauley, and Michael F. Shepard9. l or(ormln( Organization Name and Address
Washington Cooperative Fishery Research UnitCollege of Ocean and Fishery SciencesUniversity of WashingtonSeattle, WA 9819512 Sponsoring Organization Nomo and Address
National Coastal Ecosystems Team U.S. Army Corps of EngineersFish and Wildlife Service Waterways Experiment StationU.S. Department of the Interior P.O. Box 631Washington, DC 20240 Vicksburg, MS 39180
This Species Profile of the coho salmon (Oncorhynchus kisutch) is designed to givebackground material on virtually all aspects of the fish's life history. The coho isanadromous, swimming upstream from the ocean in fall to spawn. The fry hatch in thespring and outmigrate 1 to 2 years later. They usually spend two growing seasons atsea. They require clear, cold, well-oxygenated (<4 mg/l) stream water- (1 m/sec) forspawning and rearing, with a gravel substrate, adequate cover, and a food supply ofinsects, crustaceans, and fishes for the young. All populations of coho salmon arelimited by the amount of suitable rearing area available. They are sought after in bothsport and commercial fisheries, and are very sensitive, especially the early life stagesin streams, to such human-made impacts as siltation, pollution, removal of cover, andbarriers to migration.
Current management objectives of the State of Washington are toward MSH (maximumsustained harvest), with the treaty Indian tribes under the Boldt Decision (United Statesvs. State of Washington) having a legal right to 50% of the catchable allocation.
1 7 . Document Analyysis a Description
Salmon Life cyclesFisheries GrowthFeeding habitsAnimal migrations
b. Identifiers/ Open-Ender Trerms
Coho salmonOncorhynchus kisutchEnvironmental requirements
a. Availability S t a t e m e 1 9 . Security Classs ( t h i s report 21. NO . Ot Pages
Unclassified 18 --_I 22. Price
Unclassified JCA FORM 272 :4-t7)
Release unlimited 18)
U.S.G.P.O. 1986/661-638
