(DRAFT) - Taxonomy
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
TAXONOMY
NAME - salmon, coho
OTHER COMMON NAMES - coho salmon, silver salmon, silver trout (in freshwater), coho, sea trout, blueback and hooknose
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Vertebrata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Salmoniformes,
FAMILY AND SUBFAMILY - Salmonidae,
GENUS AND SUBGENUS - Oncorhynchus,
SPECIES AND SSP - kisutch,
SCIENTIFIC NAME - Oncorhynchus kisutch
AUTHORITY - Walbaum
TAXONOMY REFERENCES - 88 and 232
COMMENTS ON TAXONOMY -
Common names include coho salmon, silver salmon, silver trout (in
freshwater), coho, sea trout, blueback, and hooknose *88*.
Caution must be used when extending information from one stock of coho
salmon to another stock. Environmental conditions of one area must not be
treated as absolute; the stocks (races) have acclimated or evolved over time
and space to habitat conditions that can vary greatly *232*.
Taxonomy - 1 (DRAFT) - Status
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Commercial/consumption
Migrant
Existing, FMP exists
See Comments
REFERENCES FOR STATUS - 88 and 232
COMMENTS ON STATUS -
Coho salmon constitute a valuable part of the commercial and sport fisheries
of the west coast freshwater and marine environments. They are the object
of extensive hatchery rearing and release programs *88*.
The Alaska Board of Fisheries develops regulations governing the commercial,
sport, and subsistence harvest of salmon in Alaska. The Alaska Department
of Fish and Game manages salmon populations in the fresh waters of the state
and in the marine waters to the 3-mi limit *232*.
The North Pacific Fishery Mangaement Council is composed of 15 members, 11
voting and 4 nonvoting members. The 11 are divided as follows: 5 from
Alaska, 3 from Washington, and 3 from state fishery agencies (Alaska,
Washington, Oregon). The four nonvoting members include the director of the
Pacific Marine Fisheries Commission, the director of the U.S. Fish and
Wildlife Service, the commander of the 17th Coast Guard District, and a
representative from the U.S. Department of State. The council prepares
fishery management plans, which become law and apply to marine areas between
the 3-mi limit and the 200-mi limit. With regard to salmon, the only plan
prepared to date is the Salmon Power Troll Rishery Management Plan *232*.
The International North Pacific Fisheries Commission (INPFC), a convention
comprised of Canada, Japan, and the United States, has been established to
provide for scientific studies and for coordinating the collection,
exchange, and analysis of scientific data regarding anadromous species.
With regard to salmon, the INPFC has also prepared conservation measures
that limit the location, time, and number of fishing days that designated
high seas (beyond the 200-mi limit) areas may be fished by Japanese
nationals and fishing vessels *232*.
Coho salmon are anadromous and migrate into freshwater to spawn *232*.
Status - 1 (DRAFT) - Distribution
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine OW0 V 1
Marine OW0 V 1
Riverine SB1 H 0
Riverine SB1 H 0
Riverine SB1 H 0
REFERENCES FOR NWI - 88
COMMENTS ON HABITAT ASSOCIATIONS -
Coho salmon are anadromous, entering freshwater to spawn. Early studies
indicated that coho salmon did not migrate far offshore, but more recent
high-seas research has shown differently. They have been captured as far
as 1,930 km away from their point of origin on the North American west
coast. As a rule, adult coho salmon spend two growing seasons at sea, and
then return to their natal streams to spawn. The fish usually spawn in
small streams, but also use large main streams, though seldom more than 240
km above the mouth. They spawn in relatively fast water (0.3 to 0.5 m/sec
vs. 0.1 m/sec for sockeye), normally in riffles or where ground seepage
occurs. Redds (nests) are dug out in gravel. Fry live in shallow gravel
areas. Optimum rearing habitat for coho consists of a mixture of pools and
riffles, abundant instream and bank cover, water temperatures that average
between 10 and 15 deg C in the summer, dissolved oxygen near saturation,
and low amounts of fine sediment *88*.
Habitat Associations - 1 (DRAFT) - Food Habits
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 88 and 232
LIFESTAGE FOOD FOOD PART
General Crustaceans Larva stage
General Osteichthyes Not Specified
Adult Osteichthyes Not Specified
Adult Clupeiformes Not Specified
Adult Salmoniformes Not Specified
Adult Perciformes Juvenile stage
Juvenile Crustaceans Larva stage
Juvenile Crustaceans Not Specified
Juvenile Insects Not Specified
Juvenile Plecoptra Not Specified
Juvenile Ephemeroptera Not Specified
Juvenile Diptera Not Specified
Juvenile Osteichthyes Not Specified
Juvenile Salmoniformes Juvenile stage
Juvenile Clupeiformes Not Specified
Juvenile Polychaetes Not Specified
Juvenile Brachiopods Larva stage
Juvenile Perciformes Juvenile stage
Important Osteichthyes Not Specified
Important Crustaceans Larva stage
Juvenile Insects:terrestrial Not Specified
Juvenile Diptera Not Specified
Juvenile Diptera Larva stage
Juvenile Diptera Pupa stage
Juvenile Diptera Adult stage
Juvenile Hymenoptera Not Specified
Juvenile Homoptera Not Specified
Juvenile Thysanoptera Not Specified
Juvenile Invertebrate Cordates Not Specified
Juvenile Arachnids Not Specified
Juvenile Coleoptera Not Specified
Juvenile Collembola Not Specified
Juvenile Zooplankton Not Specified
Juvenile Zooplankton Not Specified
Juvenile Salmoniformes Juvenile stage
Juvenile Crustaceans Not Specified
Juvenile Clupeiformes Not Specified
Juvenile Perciformes Not Specified
Juvenile Osteichthyes Not Specified
Juvenile Molluscs Not Specified
Juvenile Squid, Octopus Not Specified
Adult Osteichthyes Not Specified
Adult Invertebrate Cordates Not Specified
Adult Clupeiformes Not Specified
Adult Salmoniformes Not Specified
Food Habits - 1 (DRAFT) - Food Habits
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
LIFESTAGE FOOD FOOD PART
Adult Myctophiformes Not Specified
Adult Atheriniformes Not Specified
Adult Gadiformes Not Specified
Adult Perciformes Not Specified
Adult Molluscs Not Specified
Adult Squid, Octopus Not Specified
Adult Cirripeds Not Specified
Adult Malacostraca Not Specified
Adult Cnidaria Not Specified
Adult Crustaceans Not Specified
General Myctophiformes Not Specified
Juvenile See Comments; Food See Comments
Adult See Comments; Food See Comments
General See Comments; Food See Comments
REFERENCES FOR GENERAL FOOD - 88 and 232
REFERENCES FOR IMPORTANT FOOD - 88
REFERENCES FOR ADULT FOOD - 88 and 232
REFERENCES FOR JUVENILE FOOD - 88 and 232
REFERENCES FOR LARVAE FOOD - 88
COMMENTS ON FOOD -
Coho salmon fill different niches in freshwater and in saltwater. The
alevins living in gravel do not feed, but depend on the yolk sac for
nourishment. Even though part of the yolk sac may remain after emergence,
the fry begin to feed immediately after emergence. Juvenile salmon in
Washington, depending on the season and stream, ate various lifestages of
aquatic insects (mostly at the surface), such as dipterans, ephemeropterans,
plecopterans, and other insects, as well as crustaceans and fishes. If
their normal food is scarce, juvenile coho will eat insect exuviae, even
though this provides no nutrition. Alaskan coho fingerlings prey on
sockeye salmon fry (Onchorhynchus nerka); 30% of coho captured between May
and July had sockeye remains in their stomachs. They ate the sockeye even
though sticklebacks were more abundant.
The food of coho salmon was categorized by zones in the Puget Sound and
other Washington marine waters. Juvenile fish from sublittoral habitats had
stomach contents consisting mainly of decapod crustacean larvae, plus fishes
(mostly herring), amphipods, and polychaetes. In the nearshore pelagic
zone, some juveniles examined had brachyuran crab larvae as their primary
food item. Young coho from the offshore pelagic zone ate euphausids, fishes
(mainly herring), gammarids, and decapod larvae. Fishes formed the highest
biomass, but occurred in only 30% of the coho salmon stomachs. Offshore in
the Pacific, near the Columbia River, young adult coho examined were larger
than those in Puget Sound and ate mostly fishes, including anchovy, surf
smelt, whitebait smelt, herring, juvenile chinook, and juvenile rockfish.
They also fed on euphausids and crab larvae off Oregon and Washington. In
the Great Lakes, coho and other salmon have confirmed hopes that they would
Food Habits - 2 (DRAFT) - Food Habits
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
consume the smelt and alewives present there in abundance *88*.
Types of Feeding Areas Used: Young juveniles feed in low-velocity areas
along streambanks and in backwater pools and current eddies. Feeding is
generally near the surface, with drifting invertebrates the prey; young coho
salmon feed infrequently on bottom-dwelling organisms. As they grow in
size, the juveniles may become serious predators of other small fish,
including other salmon species. When the young coho salmon migrate to the
sea, they tend to stay fairly close to shore at first. The oceanic
movements of coho salmon in the southern part of the range (i.e.,
Washington, Oregon, British columbia) seem to be chiefly along the coast,
with some fish apparently never venturing far from the coast. By contrast,
northern fish, particularly those from Alaska streams, spread out all across
the North Pacific and into the Bering Sea. Available evidence from
commercial fishries and research vessels indicates that while at sea coho
salmon occur most frequently near the surface. Individuals have been taken
at greater depths, but most coho salmon have been caught in the upper 10 m
*232*.
Factors Limiting Availability of Food: Sedimentation is one of the major
factors affecting freshwater food availability. Excessive sedimentation may
inhibit production of aquatic plants and invertebrate fauna. Primary food
production is lowered above levels of 25 JTU (Jackson Turbidity Unit) and
visual references lost above levels of 30 JTU *232*.
Feeding Behavior: Food varies from place to place and with time. While on
the high seas, schools may become involved in a feeding frenzy and have been
found to be eating blue lanternfish and sauries. Upon entering fresh water,
adult salmon no longer feed but live off the fat they stored up while in the
ocean *232*.
COMMENTS ON ADULT FOOD -
Offshore in the Pacific, near the Columbia River, young adult coho examined
were larger than those in Puget Sound and ate mostly fishes, including
anchovy, surf smelt, whitebait smelt, herring, juvenile chinook, and
juvenile rockfish. They also fed on euphausids and crab larvae off Oregon
and Washington. In the Great Lakes, coho and other salmon have confirmed
hopes that they would consume the smelt and alewives present there in
abundance *88*.
The food of marine adults is more pelagic and more varied than that of many
Pacific salmon. Fishes make up 70 to 80% of the coho salmon's food,
invertebrates 20 to 30%, and include the following: pilchard, herring,
anchovy, coho salmon, capelin, lanternfish, Pacific saury, hake, whiting,
rockfishes, black cod, sculpins, sand lance, squid, barnacles, isopods,
amphipods, euphausiids, crab larvae, and jelly fish. Herring and sand lance
make up 75% of the volume. Some populations, however, remain on the
crustacean diet, such coho generally not growing as big as those that eat
fish *232*.
COMMENTS ON JUVENILE FOOD -
Juvenile salmon in Washington, depending on the season and stream, ate
various life stages of aquatic insects (mostly at the surface), such as
Food Habits - 3 (DRAFT) - Food Habits
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
dipterans, ephemeropterans, plecopterans, and other insects, as well as
crustaceans and fishes. If their normal food is scarce, juvenile coho will
eat insect exuviae, though this provides no nutrition. Alaskan coho
fingerlings prey on sockeye salmon fry; 30% of coho captured between May
and July had sockeye remains in their stomachs. They ate the sockeye even
though sticklebacks were more abundant.
The food of coho salmon was categorized by zones in the Puget Sound and
other Washington marine waters. Juvenile fish from sublittoral habitats had
stomach contents consisting mainly of decapod crustacean larvae, plus fishes
(mostly herring), amphipods, and polychaetes. In the nearshore pelagic
zone, some juveniles examined had brachyuran crab larvae as their primary
food item. Young coho from the offshore pelagic zone ate euphausids, fishes
(mainly herring), gammarids, and decapod larvae. Fishes formed the highest
biomass, but occurred in only 30% of the coho salmon stomachs. Offshore in
the Pacific, near the Columbia River, young adult coho examined were larger
than those in Puget Sound and ate mostly fishes, including anchovy, surf
smelt, whitebait smelt, herring, juvenile chinook, and juvenile rockfish.
They also fed on euphausids and crab larvae off Oregon and Washington. In
the Great Lakes, coho and other salmon have confirmed hopes that they would
consume the smelt and alewives present there in abundance *88*.
Upon hatching, young alevin remain in the gravel for two or three weeks
until the yolk sack has been absorbed. Following emergence from the gravel,
the juveniles begin feeding at or near the surface. Major food items at
this time are terrestrial insects, especially species of flies (Diptera) and
wasps and bees (Hymenoptera), and perhaps also aphids and thrips. Midges
(chironomids) were dominant in stomach samples of juvenile coho salmon in
the Kenai River, Alaska. Juvenile coho salmon food habit studies during
August and September in sloughs and clearwater tributaries of the middle
reach of the Susitna River suggest that the range and diversity of
invertebrates in their diet indicate an ability to adapt to variable
conditions. Specimens collected during the study had consumed both
terrestrial and aquatic invertebrates. Based on numbers consumed, they
relied mainly on midge (Diptera: Chironomidae) larvae, pupae and adults.
Although not contributing much in terms of dry wieght, the major components
of their terrestrial diet were usually small aphids (Homoptera: Aphidae),
small Depterans (Phoridae, Simuliidae, and Scaridae), and small (less than 5
mm) Hymenopterans. The diet can also include mites, beetles, springtails
(Collembola), spiders, and small zooplankton. As the young fish grow they
consume larger food items and often consume young sockeye salmon. In
Chignik Lake, Alaska, young coho salmon have been found to eat seven times
as many juvenile sockeye salmon as do Dolly Varden, and in other localities
coho salmon may be equally serious predators. Large numbers of chum and
pink salmon are also taken by coho salmon. Upon entering the sea, young
coho feed on various planktonic crustaceans, pink and chum salmon fry,
herring, sand lance, other fishes, and squid *232*.
COMMENTS ON LARVAE FOOD -
Coho alevins living in gravel do not feed, but depend on the yolk sac for
nourishment *88*.
Food Habits - 4 (DRAFT) - Environment Associations
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
ENVIRONMENTAL ASSOCIATIONS
Environment Associations - 1 (DRAFT) - Life History
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
LIFE HISTORY
Life History - 1 (DRAFT) - Management Practices
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Existing Regulating harvest of species being described
Beneficial Maintaining/protecting riparian habitats
Beneficial Stocking captive-reared wild-strain animals
Beneficial Developing/maintaining suitable pH
Beneficial Controlling water levels
Beneficial Controlling sedimentation
Beneficial Establishing/maintaining nesting and escape cover
Beneficial Developing/maintaining stream bank vegetation
Beneficial Developing/maintaining stream structures
Beneficial Regulating harvest of species being described
Beneficial Other management practices [specified in comments]
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 88 and 232
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 88
COMMENTS ON MANAGEMENT PRACTICES -
Current management objectives of the Washington Department of Fisheries are
toward maximum sustained harvest, with the treaty Indian Tribes under the
Boldt Decision (United States vs. State of Washington) having a legal right
to 50% of the catchable allocation. Preseason run sizes for each individual
river are estimated and escapement goals for each river are predicted; an
escapemant goal is the number of spawners necessary to maintain the run of a
given size, and a goal may vary from year to year. In-season run
reassessments are also made. From these predictions and projections each
year, the catchable allocation of coho salmon in each individual river is
made with non-Indians receiving 50% and treaty Indians receiving 50%. The
non-Indian share is then divided between commercial fishermen and sport
anglers.
Management methods for coho and other salmon must include freshwater habitat
assessment, stock assessment including run size, habitat protection and
improvement, and artificial propogation. The Washington Department of
Fisheries has been using Smoker's preseason method in Puget Sound to predict
coho salmon catches from stream discharge data, as well as the previous
year's jack run size. Such factors, however, as environmental extremes,
saltwater environmental variations, and fishing intensity also play a role.
Other methods are being developed and used in other areas by cooperative
efforts between State biologists and tribal biologists.
Good run forecasts with accurate and timely reassessments are important in
salmon management. Also, runs dependent on hatcheries could be harvested at
a higher rate than wild runs because of high survival of juveniles in
hatcheries. Where two stocks coexist geographically, maximum sustained
yield should be defined for the weaker stock, with the surplus fish taken
where the stronger stock is easier to target. There are arguments against
depending on user groups, i.e., fishermen, for sound management; the
vitality of the resource should be the primary criterion used in designing
management procedures *88*.
Management Practices - 1 (DRAFT) - Management Practices
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
A summary of possible impacts from human-related activities includes:
alteration of preferred water temperature, pH, dissolved oxygen, and
chemical composition; alteration of preferred water velocity and depth;
alteration of preferred stream morphology; increase in suspended organic or
mineral material; increase in sedimentation and reduction in permeability of
substrate; reduction in food supply; reduction in protective cover (e.g.,
overhanging stream banks or vegetation); shock waves in aquatic environment;
and human harvest *232*.
Management Practices - 2 (DRAFT) - References
Species salmon, coho
Species Id M0100271
Date 26 AUG 96
References
References - 1