(DRAFT) - Taxonomy
Species salmon, pink
Species Id M010005
Date 26 AUG 96
TAXONOMY
NAME - salmon, pink
OTHER COMMON NAMES - pink salmon, pinks, humpback, humpback salmon and humpy
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Chordata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Salmoniformes,
FAMILY AND SUBFAMILY - Salmonidae,
GENUS AND SUBGENUS - Oncorhynchus,
SPECIES AND SSP - gorbuscha,
SCIENTIFIC NAME - Oncorhynchus gorbuscha
AUTHORITY - Walbaum
TAXONOMY REFERENCES - 12 and 232
COMMENTS ON TAXONOMY -
Caution must be used when extending information from one stock of pink
salmon to another stock. Environmental conditions for 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, pink
Species Id M010005
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Migrant
Existing, FMP exists
Commercial/consumption
Subsistence
International treaty
See Comments
REFERENCES FOR STATUS - 12 and 232
COMMENTS ON STATUS -
Pink salmon are the most abundant of the species of Pacific salmon. They
spawn in North American and Asian streams bordering the Pacific and Arctic
Oceans. Their range in North America is extensive; they are the most
numerous salmon in the commercial salmon fisheries with a very high rate of
exploitation by Canadian, Japanese, Russian, and United States commercial
fishermen *12*.
Freshwater streams and rivers serve as downstream migration corridors for
ocean-bound juveniles and as upstream migration pathways for spawning adults
*232*.
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-mile limit *232*.
North Pacific Management Council:
There is a Salmon Power Troll Fishery Management Plan which is federal law
and applies to marine areas between the 3-mile limit and the 200-mile limit
*232*.
International North Pacific Fisheries Commission (INPFC):
The INPFC has prepared conservation measures that limit the location, time,
and number of fishing days that designated high seas areas (beyond the
200-mile limit) may be fished by Japanese nationals and fishing vessels
*232*.
Status - 1 (DRAFT) - Distribution
Species salmon, pink
Species Id M010005
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 12
LAND USE -
Water
Streams and Canals
Lakes
Bays and Estuaries
REFERENCES FOR LAND USE - 12
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Estuarine, intertidal
Riverine 0
Riverine 0
Riverine 0
Marine
Marine
Lacustrine
REFERENCES FOR NWI - 12
COMMENTS ON HABITAT ASSOCIATIONS -
The salmon return to their stream of origin to spawn in the fall when the
water temperature ranges from 8 to 14 C, and usually enter the river on
high water freshets. Some pink salmon spawn several miles upstream from
saltwater in a few river systems, but spawning generally takes place either
in freshwater close to the sea or in the intertidal zones. Pink salmon are
considered the most specialized of the salmon in the genus Oncorhynchus
because they are the least dependent on freshwater, regularly spawning in
the intertidal areas. Spawning usually occurs in late August through early
October in much of the range. The female digs a depression in the gravel
on the stream bottom in an area averaging 0.6 to 0.9 m in width, and in
water with an average depth of 0.15-0.53 m and velocity of 21-100 cm/s.
The tail is used to force water down on the gravel to remove fine
sediments.
Fry are abundant in marsh area tidal channels. Unlike chinook and chum
salmon fry which reside temporarily in the marsh before migrating into the
Pacific Ocean, pink salmon fry appear to be only transient residents of the
estuarine marsh area as they make their rapid and active migrations
downstream. After leaving freshwater, the young tend to remain close
inshore during their first summer. In the intertidal regions, the young
salmon prefer feeding in water of relatively low salinity.
Migration in the sea is saltatory, with short periods of active migration
interspersed with longer periods when the fry do not migrate. Theories for
the control of marine migration include movement toward higher salinities
and the use of tidal flow and food gradients.*12*
Freshwater streams and rivers serve as downstream migration corridors for
ocean-bound juveniles and as upstream migration pathways for spawning adults
*232*.
At the beginning of their ocean migrations, pink salmon from Washington,
Oregon, and Southern British Columbia move northward from their streams of
origin in a narrow belt along the coast. Substantial numbers of fish from
British Columbia stocks move up to 500 miles offshore. The vertical
Habitat Associations - 1 distribution of pink salmon in the ocean is not well known. Gillnet and
longline catches on which knowledge of horizontal distribution is based are
usually made within 6 to 7 m of the surface. In the Gulf of Alaska, some
fish have been caught at depths of 24 to 36 m *12*.
Food of juveniles in protected waters such as Chatham Sound, Alaska, and
Puget Sound, Washington, includes harpacticoid copepods, copepod nauplii,
invertebrae eggs, tunicates, and barnacle larvae *232*.
An examination of fry stomach contents taken from Lake Aleknagik
during July revealed that zooplankton (i.e., Bosmina, Daphnia,
Holopedium, Cyclopoida, and Calanoida) made up the bulk of the food *232*.
ANIMAL/PLANT SPECIES ASSOCIATIONS -
Cutthroat trout
Rainbow trout
Dolly Varden
Coho salmon
Sculpin
Kingfisher
Merganser
Pacific lamprey
Artic lamprey
REFERENCES FOR SPECIES ASSOCIATIONS - 232
COMMENTS ON SPECIES ASSOCIATIONS -
Juveniles are preyed upon by a variety of fishes (e.g., cutthroat and
rainbow trout, Dolly Varden, coho salmon smolts, and sculpins), kingfisher,
mergansers, and other predaceous birds and mammals. Mortality during early
sea life (first 40 days) is fairly high at 2 to 4% per day, where predation
by birds, fishes, and various invertebrates may be an important factor in
mortality at this time. Adults at sea are preyed upon by marine mammals,
Pacific and arctic lamprey, and to a lesser extent by large fish *232*.
Habitat Associations - 2 (DRAFT) - Food Habits
Species salmon, pink
Species Id M010005
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 12 and 232
LIFESTAGE FOOD FOOD PART
Juvenile Crustaceans Larva stage
Juvenile Crustaceans Not Specified
Juvenile Zooplankton Not Applicable
Juvenile Copepods Egg/Fetus stage
Juvenile Copepods Not Specified
Juvenile Cirripeds Larva stage
Juvenile Malacostraca Not Specified
Juvenile Insects Larva stage
Juvenile Insects: aquatic Larva stage
Juvenile Diptera Larva stage
Juvenile Invertebrate Cordates Not Specified
Juvenile Fish Not Specified
Juvenile See Comments; Food
Adult Molluscs Not Specified
Adult Squid, Octopus Not Specified
Adult Crustaceans Not Specified
Adult Copepods Not Specified
Adult Malacostraca Not Specified
Adult Fish Not Specified
Adult See Comments; Food
Juvenile Insects Juvenile stage
Juvenile Zooplankton Not Specified
Juvenile Zooplankton Not Specified
Juvenile Ostracods Not Specified
Juvenile Malacostraca Larva stage
Juvenile Cirripeds Not Specified
Juvenile Sea Squirts Not Specified
Juvenile Diptera Not Specified
Juvenile Cirripeds Larva stage
Juvenile Branchiopods Not Specified
Adult Osteichthyes Not Specified
REFERENCES FOR ADULT FOOD - 12 and 232
REFERENCES FOR JUVENILE FOOD - 12 and 232
COMMENTS ON FOOD -
Types of Feeding Areas Used: Because pink salmon spend such a short time in
natal waters following emergence from the gravel, little data are available
on freshwater feeding locations. Samples of pink salmon fry in Lake
Aleknagik indicate that although they were caught in the lake littoral zone
(inshore), their stomach contents indicated thay had foraged mainly in the
pelagic zone of the lake. Juvenile pink salmon school in estuarine waters
and frequent the water's edge along mainland and inland shores. They remain
Food Habits - 1 (DRAFT) - Food Habits
Species salmon, pink
Species Id M010005
Date 26 AUG 96
in nearshore areas for about a month, and when they have attained a length
of 6 to 8 cm they begin a gradual, irregular movement to offshore waters.
On the high seas, pink salmon vertical distribution has been found to range
from 10 to 23 m, although a few have been caught at depths from 24 to 36 m
*232*.
Factors Limiting Availability of Food: Because pink salmon feed very little
if at all in fresh water, the major factors limiting food availability would
be those found in the estuarine environment. Variations in weather patterns
and ocean currents, which affect dispersal of planktonic organisms, could
influence food sources for juvenile pink salmon *232*.
Feeding Behavior: Pink salmon select their food by sight and shallow it
whole. During studies of estuarine feeding habits at Traitors Cove in
Southeast Alaska, a study found that many more food items were contained in
the stomachs of juvenile pink salmon collected in daytime than in those
collected at night. It also found that the fry fed selectively. Relatively
more cladocerans, decapod zoeae, and larvaceans were eaten than appeared in
the samples of available planktonic food items. Visual observations of
individual pink salmon fry in shore-oriented schools at Traitors Cove
indicate that their feeding varied with the speed of the water current. At
velocities of 0 to 10.7 cm/s, a fry would typically swim a darting course as
much as three times its body length to capture a food item. At higher
velocities, 10.8 to 19.8 cm/s, schools of fry sometimes held position
relative to the shore or bottom while facing the current, and an individual
would typically deviate up, down, or to the sides no more than one-third of
its body length to capture oncoming food. At still higher velocities, 19.9
to 24.4 cm/s, fry in schools often held a constant position relative to
shore or bottom but did not feed. Fry that appeared to be in visual contact
with the shore or bottom avoided currents above 24.4 cm/s unless frightened.
In offshore marine waters, pink salmon appear to have a vertical feeding
pattern, with light intensity the major factor. Feeding indices of pink
salmon near surface water began to increase before sunset, attained a
maximum two to three hours after sunset, and thereafter decreased to a
minimum before sunrise. The feeding indices again became large in daytime.
Whereas the dominant organisms of the stomach contents before sunset were
large prey animals such as squids and fish larvae, the percentage of
amphipods (whose numbers increased in surface waters with darkness), as well
as feeding indices, increased after sunset, when amphipods became the main
item of diet. Darkness prevents pink salmon from seeing and feeding on
amphipods *232*.
COMMENTS ON ADULT FOOD -
Adult pink salmon feed primarily on amphipods, euphausiids, and fish *12*.
During their final summer in the high seas, the diet of pink salmon consists
of many organisms, the most important being euphausiids, amphipods, fish,
squid, copepods, and pteropods *232*.
COMMENTS ON JUVENILE FOOD -
Immediately upon emerging from the gravel, juveniles begin migrating
downstream. Migrating juveniles generally do not feed. If the distance to
the sea is great, however, they may feed on nymphal and larval insects.
Food Habits - 2 (DRAFT) - Food Habits
Species salmon, pink
Species Id M010005
Date 26 AUG 96
Studies in Lake Aleknagik and Tikchik Lake in the Bristol Bay area, however,
indicate differences in the early life histroy of pink salmon that spawn in a
lake system from those that spawn in coastal rivers. In coastal rivers, the
fry migrate to salt water upon emergence from the gravel. They are then
about 30 mm long. The young fry obtain little food from the freshwater
environment and subsist largely on the yolk. In the Wood River lakes and
Tikchik Lake, the fry must travel some distance to reach the outlet rivers
(96 km in the case of Agulukpak River fry); and it is quite apparent that
they feed actively during the course of their travel. In addition, it was
found that some of the juvenile pink salmon remained in Lake Aleknagik long
after emergence, were caught in tow net samples as late as September 10, and
had grown to mean lengths of 89 mm. An examination of stomach contents
taken from Lake Aleknagik fry revealed that zooplankton (i.e., Bosmina,
Daphnia, Holopedium, Cyclopoida, and Calanoida) made up the bulk of the
food. In nearshore salt water, the juveniles consume small crustaceans
(e.g., copepods, euphausiids, amphipods, ostracods), larvae of decapods,
cirripeds and tunicates, and dipterous insects. Pink salmon fry in Traitors
Cove of Southeast Alaska consumed estuarine food items that were mostly
between 0.3 and 3.0 mm long, with copepods (calanoids and cyclopoids)
constituting the bulk of the diet. Also found in the diet were barnacle
nauplii (cirripedes), cladocerans (Podon sp. and Evadne sp.), and various
other planktonic forms and occasional epibenthic organisms. As they grow,
the diet consists of larger items until, during their final summer in the
high seas, the diet consists of many organisms, the most important being
euphausiids, amphipods, fish, squid, copepods, and pteropods *232*.
Food of juveniles in protected waters such as Chatham Sound, Alaska, and
Puget Sound, Washington, includes harpacticoid copepods, copepod nauplii,
invertebrae eggs, tunicates, and barnacle larvae. Pink salmon co-occurring
with juvenile chum salmon of approximately the same size in Hood Canal had
an overlap in dietary items that approached 75%. The estuarine residence
time of juvenile pink salmon varies from 4 to 18 weeks. Researchers found
the preferred food of pink salmon in the ocean to be amphipods,
supplemented by fish, euphausiids, squid, and crustacean larvae. However,
differences were noted in the diets of fish close to shore versus those of
fish far from shore: for fish from inshore waters, amphipods were the most
important and crustacean larvae ranked second in importance; for fish from
offshore waters, copepods and euphausiids were the dominant food items.
Pink salmon appeared to select larger food items as they moved further
offshore. It has been hypothesized that appreciable differences in average
size of individual pink salmon in different years are probably due, in part,
to differences in feeding conditions *12*.
In the intertidal regions, the young salmon prefer feeding in water of
relatively low salinity. Preferred food includes various invertebrate eggs,
amphipods, and copepods in Puget Sound, although other planktonic organisms
are eaten elsewhere. Researchers conducted laboratory tests which showed
that 68% of the juvenile fish were most active during the day.
Stomach analyses from fry showed that most feeding occurs during daylight
hours in the littoral zone *12*.
During studies of estuarine feeding habits at Traitors Cove in Southeast
Alaska, a study found that many more food items were contained in the
Food Habits - 3 (DRAFT) - Food Habits
Species salmon, pink
Species Id M010005
Date 26 AUG 96
stomachs of juvenile pink salmon collected in daytime than in those
collected at night. It also found that the fry fed selectively. Relatively
more cladocerans, decapod zoeae, and larvaceans were eaten than appeared in
the samples of available planktonic food items. Visual observations of
individual pink salmon fry in shore-oriented schools at Traitors Cove
indicate that their feeding varied with the speed of the water current. At
velocities of 0 to 10.7 cm/s, a fry would typically swim a darting course as
much as three times its body length to capture a food item. At higher
velocities, 10.8 to 19.8 cm/s, schools of fry sometimes held position
relative to the shore or bottom while facing the current, and an individual
would typically deviate up, down, or to the sides no more than one-third of
its body length to capture oncoming food. At still higher velocities, 19.9
to 24.4 cm/s, fry in schools often held a constant position relative to
shore or bottom but did not feed. Fry that appeared to be in visual contact
with the shore or bottom avoided currents above 24.4 cm/s unless frightened
*232*.
COMMENTS ON LARVAE FOOD -
Upon hatching,young alevin remain in the gravel for several weeks until the
yolk sac has been absorbed *232*.
Food Habits - 4 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Water pH: Specified in Comments
BA Water Temperature: Between 15-21 degrees C
BA Water Temperature: Below 15 degrees C
BA Water Temperature: Specified in Comments
J Water Temperature: Specified in Comments
E Water Temperature: Specified in Comments
LIM Water Temperature: Specified in Comments
A Dissolved Oxygen: High [greater than 7 mg/l] oxygen concentrations
E Dissolved Oxygen: High [greater than 7 mg/l] oxygen concentrations
FL Dissolved Oxygen: High [greater than 7 mg/l] oxygen concentrations
BA Turbidity: Clear water
J Turbidity: Specified in Comments
E Turbidity: Specified in Comments
L Turbidity: Specified in Comments
BA Bottom Type [Aquatic]: Gravel
E Bottom Type [Aquatic]: Gravel
E Bottom Type [Aquatic]: Specified in Comments
LIM Bottom Type [Aquatic]: Specified in Comments
G Gradient: Low
G Gradient: Specified in Comments
E Water Velocity [Instream Flow Group Increments]: Specified in Comments
L Water Velocity [Instream Flow Group Increments]: Specified in Comments
BA Water Velocity [Instream Flow Group Increments]: Specified in Comments
LIM Water Velocity [Instream Flow Group Increments]: Specified in Comments
G Water Depth Preference: 25-50 ft.
G Water Depth Preference: 50-100 ft.
G Water Depth Preference: 100-200 ft.
G Water Depth Preference: Specified in Comments
BA Water Depth Preference: Specified in Comments
LIM Water Depth Preference: Specified in Comments
G Human Association: Specified in Comments
LIM Human Association: Specified in Comments
G Currents: specified in comments
LIM Currents: specified in comments
BA Water Temperature: Between 15-21 degrees C
BA Water Temperature: Below 15 degrees C
BA Water Temperature: Specified in Comments
E Water Temperature: Below 15 degrees C
E Water Temperature: Specified in Comments
LIM Water Temperature: Between 21-27 degrees C
Environment Associations - 1 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
LIM Water Temperature: Specified in Comments
J Water Temperature: Between 21-27 degrees C
J Water Temperature: Specified in Comments
J Water Temperature: Below 15 degrees C
J Water Temperature: Specified in Comments
G Water pH: Between 6.5-8.5
G Water pH: Between 8.5-10.0
G Water pH: Specified in Comments
E Dissolved Oxygen: Moderate [5-7 mg/l] oxygen concentrations
E Dissolved Oxygen: Specified in Comments
A Estuarine habitat zone: bay
A Estuarine habitat zone: specified in comments
G Dissolved Oxygen: High [greater than 7 mg/l] oxygen concentrations
G Dissolved Oxygen: Specified in Comments
E Turbidity: Specified in Comments
E Water Velocity [Instream Flow Group Increments]: Specified in Comments
E Water Depth Preference: Specified in Comments
A Water Depth Preference: Specified in Comments
A Water Depth Preference: Less than 1 ft.
E Water Depth Preference: Less than 1 ft.
E Water Depth Preference: 1-5 ft.
E Water Depth Preference: Specified in Comments
E Bottom Type [Aquatic]: Gravel
E Bottom Type [Aquatic]: Specified in Comments
E Substrate: Rocks
E Substrate: Specified in Comments
BA Bottom Type [Aquatic]: Gravel
BA Bottom Type [Aquatic]: Specified in Comments
BA Substrate: Rocks
BA Substrate: Specified in Comments
L Substrate: Rocks
L Substrate: Specified in Comments
FJ Aquatic Habitat Zonation: Open water [pelagic zone]
FJ Aquatic Habitat Zonation: Specified in Comments
FJ Coastal Features: Specified in Comments
FA Water Depth Preference: 25-50 ft.
FA Water Depth Preference: 50-100 ft.
FA Water Depth Preference: Specified in Comments
BA
BA Water Depth Preference: Specified in Comments
BA Gradient: Low
BA Gradient: Specified in Comments
E Dissolved Oxygen: Specified in Comments
E Water Temperature: Specified in Comments
E Water Velocity [Instream Flow Group Increments]: Specified in Comments
E Substrate: Specified in Comments
E Gradient: Specified in Comments
E Water Depth Preference: Specified in Comments
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 232
Environment Associations - 2 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 232
REFERENCES FOR ADULT ENVIRONMENTAL ASSOC_ - 12 and 232
REFERENCES FOR FEEDING ADULT ENVIRONMENTAL ASSOC_ - 232
REFERENCES FOR BREEDING ADULT ENVIRONMENTAL ASSOC_ - 12 and 232
REFERENCES FOR JUVENILE ENVIRONMENTAL ASSOC_ - 232
REFERENCES FOR FEEDING JUVENILE ENVIRONMENTAL ASSOC_ - 232
REFERENCES FOR LARVAE ENVIRONMENTAL ASSOC_ - 232
REFERENCES FOR FEEDING LARVAE ENVIRONMENTAL ASSOC_ - 12
REFERENCES FOR EGG ENVIRONMENTAL ASSOC_ - 12 and 232
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
TURBIDITY
Excess turbidity from organic materials in the process of oxidation may
reduce oxygen below safe levels, and sedimentation may smother food
organisms and reduce primary productivity *232*.
PH FACTOR
There is no optimum pH value for fish in general; however, in waters where
good fish fauna occur, the pH usually ranges between 6.7 and 8.3. State of
Alaska water quality criteria for freshwater growth and propagation of fish
call for pH values of not less than 6.5 or greater than 9.0, with variances
of no more than 0.5 pH unit from natural conditions *232*.
WATER DEPTH
On the high seas, pink salmon vertical distribution has been found to range
from 10 to 23 m, although a few have been caught at depths from 24 to 36 m
*232*.
FACTORS LIMITING AVAILABILITY OF FOOD (WEATHER PATTERNS, OCEAN CURRENTS)
Because pink salmon feed very little if at all in fresh water, the major
factors limiting food availability would be those found in the estuarine
environment. Variations in weather patterns and ocean currents, which
affect dispersal of planktonic organisms, could influence food sources for
juvenile pink salmon *232*.
GRADIENT
The grounds that are intensively occupied by pink salmon tend to have a
relatively low gradient *232*.
POSSIBLE IMPACTS FROM HUMAN RELATED ACTIVITIES
A summary of possible impacts from human-related activities includes the
following:
- 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
Environment Associations - 3 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
vegetation
- Shock waves in aquatic environment
- Human harvest *232*
State of Alaska water quality critieria for growth and propagation of fish
state that D.O. shall be greater than 7 mg/l in waters used by anadromous
and resident fish. In no case shall D.O. be less than 5 mg/l to a depth of
20 cm in the interstitial waters of gravel utilized by anadromous or
resident fish for spawning. In no case shall D.O. above 17 mg/l be
permitted. The concentration of total dissolved gas shall not exceed 110%
of saturation at any point of sample collection *232*.
COMMENTS ON LIMITING ENVIRONMENTAL ASSOC_ -
WATER TEMPERATURE:
Egg hatching rates are influenced by water temperature. Abnormally warm or
cold water can accelerate or depress developmental rates and cause
premature or delayed fry emergence. Laboratory tests have shown that eggs
require at least 4.5 degrees C water tempertures from the time the egg is
deposited in the redd through the gastrula stage of development *232*.
Freezing of eggs during periods of severe and prolonged cold is listed as
one of five principle causes of death of eggs *232*.
The upper lethal temperature limit for pink salmon juveniles from
Washington was experimentally determined to be 23.9 oC *232*.
DISSOLVED OXYGEN:
It has been recommended that for successful development of pink salmon eggs
and alevins the DO level should exceed 6.0 mg/l. Dissolved oxygen levels
below 6.0 mg/l apparently cause premature emergence, decreased size, and
low survival *232*.
State of Alaska water quality criteria for growth and propagation of fish
state that "D.O. shall be greater than 7 mg/l in waters used by anadromous
and resident fish. Further, in no case shall D.O. be less than 5 mg/l to a
depth of 20 cm in the interstitial waters of gravel utilized by anadromous
or resident fish for spawning. In no case shall D.O. above 17 mg/l be
permitted. The concentration of total dissolved gas shall not exceed 110%
of saturation at any point of sample collection" *232*.
INSTREAM FLOW
Adults returning to spawning grounds may be blocked if current velocities
exceed 2.1 m/sec. Low flows and shallow water depths can also block
upstream migration *232*.
WATER DEPTH
It has been suggested that adult pink salmon need a minimum of about 0.18 m
water depth for upstream passage. These values will vary with the size and
condition of adult pink salmon and the length of stream reach with shallow
water. Pink salmon have been observed passing over shallow riffles less
than 0.09 m deep in the Kizhuyak and Terror rivers on Kodiak Island *232*.
SUBSTRATE
Egg and alevin development is influenced by substrate composition because
increased amount of small material (fines) can reduce intragravel water
flow. Productive pink salmon streams generally contain fines (0.833 mm
diameter) contributing less than 5% of the volume of the substrate. They
also found that less productive streams were characterized by 15% or more
fines in the substrate *232*.
Environment Associations - 4 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
FACTORS LIMITING AVAILABILITY OF FOOD (WEATHER PATTERNS, OCEAN CURRENTS)
Because pink salmon feed very little if at all in fresh water, the major
factors limiting food availability would be those found in the estuarine
environment. Variations in weather patterns and ocean currents, which
affect dispersal of planktonic organisms, could influence food sources for
juvenile pink salmon *232*.
POSSIBLE IMPACTS FROM HUMAN RELATED ACTIVITIES
A summary of possible impacts from human-related activities includes the
following:
- 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
- Human harvest *232*
COMMENTS ON ADULT ENVIRONMENTAL ASSOC_ -
Adult pink salmon are cold-water fish with a preferred temperature range of
5.6 to 14.6 C, an optimal temperature of 10.1 C, and an upper lethal
temperature of 25.8 C. The relatively high stream temperatures (17 C) and
low dissolved oxygen levels associated with drought conditions have
apparently killed many mature adult pink salmon in Alaskan streams.*12*
Turbid water will absorb more solar radiation than clear water and may thus
indirectly raise thermal barriers to the adult's upstream spawning
migration *232*.
COMMENTS ON FEEDING ADULT ENVIRONTAL ASSOC_ -
On the high seas, pink salmon vertical distribution has been found to range
from 10 to 23 m, although a few have been caught at depths from 24 to 36 m
*232*.
COMMENTS ON BREEDING ADULT ENVIRONMENTAL ASSOC_ -
WATER TEMPERATURE
The optimum water temperatures for pink salmon spawning range from 7.2 to
12.8 C.
Pink salmon in Southeast Alaska have been observed to spawn in water
temperatures ranging from 7.4 to 18.3 degrees C. The preferred range
appears to be 7.2 to 12.8 degrees C *232*.
SUBSTRATE
It is estimated that over 50% of the pink salmon spawning
activity in Prince William Sound, Alaska occurs in intertidal areas.
The diameter of gravel that composes the substrate for spawning pink salmon
ranges from 1.3 to 10.2 cm. Pink salmon spawn over a variety of substrate
materials. The size, shape, density, and embeddedness of the material,
current velocity, water depth, and densities of fish can influence
substrate selection. Successful fry emergence is physically hindered by
excessive amounts of sand and silt in the gravel, which also limit the
Environment Associations - 5 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
Environment Associations - 6 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
percolation of water with its DO content. It has been suggested that small
gravels made ideal pink salmon spawning areas. No differences in size or
time of return of adults could be traced to the nature of the gravel
environment from which they came.*12*
Pink salmon spawn over a variety of substrates ranging widely in size and
compostion. Adults generally select areas with a relatively low gradient
combined with beds of small-to-medium-size gravel (1.3 to 10 cm diameter)
*232*.
WATER DEPTH
Water depth selected by pink salmon is determined by current velocity and
substrate type. Preferred water depths for spawning pink salmon in selected
Washington State streams ranged from 0.2 to 0.5 m.
It has been suggested that adult pink salmon need a minimum of about 0.18 m
water depth for upstream passage. These values will vary with the size and
condition of adult pink salmon and the length of stream reach with shallow
water. Pink salmon have been observed passing over shallow riffles less
than 0.09 m deep in the Kizhuyak and Terror rivers on Kodiak Island *232*.
WATER VELOCITY
Although several current velocites are suitable for pink salmon spawning,
the preferred velocities range from 21 to 101 cm/s. Pink salmon in the
Terror River, Alaska, spawned in areas with current velocites ranging from
0.19 to 0.66 m/s, but the preferred spawning velocities ranged from 0.35 to
0.47 m/s. Flow regimes can affect developing pink salmon eggs and alevins
through either mechanical damage, temperature changes, or reduced
intragravel dissolved oxygen levels. The high current velocities associated
with high stream discharges sometimes exceed the swimming capabilities of
pink salmon and prevent upstream migration. However, pink salmon can
negotiate current velocities up to about 2.1 m/s. Upstream migrations of
adults can be hampered by either too little or too much stream flow.*12*
Water velocity at spawning locations as measured at 0.16 m above the
substrate has ranged from 0.1 to 1.32 m/sec, and the preferred range
appears to be about 0.35 to 0.75 m/sec as measured by mean column velocity.
Use of waters outside the preferred ranges may in large part be due to
crowding on the spawning grounds *232*.
Migrating salmon avoid or cease to migrate in waters with very high silt
loads (4,000 mg/l). Turbid water absorbs more radiation than clear water,
thus possibly resulting in temperature barriers to upstream migration.*12*
Adults returning to spawning grounds may be blocked if current velocities
exceed 2.1 m/sec. Low flows and shallow water depths can also block
upstream migration. Adult pink salmon need a minimum of about 0.18 m water
depth for upstream passage. These values will vary with the size and
condition of adult pink salmon and the length of stream reach with shallow
water. Pink salmon have been observed passing over shallow riffles less
than 0.09 m deep in the Kizhuyak and Terror rivers on Kodiak Island *232*.
In some instances spawning takes place in stream mouth areas where water
levels change with the tides and where varying degrees of salinity are
experienced. In small coastal stream the upstream limit is usually defined
by a waterfall situated within a few miles of the sea. In larger rivers
without major obstructions, the end-point may be less definite. The
grounds that are intensively occupied by pink salmon tend to have a
Environment Associations - 7 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
relatively low gradient *232*.
COMMENTS ON JUVENILE ENVIRONMENTAL ASSOC_ -
WATER TEMERATURE:
The upper lethal temperature limit for pink salmon juveniles from
Washingtaon was experimentally determined to be 23.9 degrees C, but lower
lethal limits were not determined. Juveniles have been found to prefer 12
to 14 degrees C temperatures *232*.
DISSOLVED OXYGEN:
Growth rate, food consumption, and efficiency of food utilization by
juvenile salmon all declined at lowered DO. Reduced DO concentrations can
significantly hamper the swimming performance of migrating adult
salmonids.*12*
TURBIDITY
Prolonged exposure to turbid water causes gill irritation in juveniles,
which can result in fungal and pathogenic bacterial infection *232*.
COMMENTS ON RESTING JUVENILE ENVIRONMENTAL ASSOC_ -
Increased turbidity also may cause osmoregulatory problems in young fish by
interferring with gill function. This results in delayed entry into
seawater and increased predation on the estuarine population.*12*
COMMENTS ON FEEDING JUVENILE ENVIRONMENTAL ASSOC_ -
Juvenile pink salmon encounter a wide range of salinities in their
migrations. Salinity gradients are thought to play a part in salmon
migrations *12*.
Samples of pink salmon fry in Lake Aleknagik indicate that although they
were caught in the lake littoral zone (inshore), their stomach contents
indicated they had foraged mainly in the pelagic zone of the lake.
Juvenile pink salmon school in estuarine waters and frequent the water's
edge along mainland and inland shores. They remain in nearshore areas for
about a month, and when they have attained a length of 6 to 8 cm they begin
a gradual, irregular movement to offshore waters *232*.
Visual observations of individual pink salmon fry in shore-oriented schools
at Traitors Cove indicate that their feeding varied with the speed of the
water current. At velocities of 0 to 10.7 cm/s, a fry would typically swim
a darting course as much as three times its body length to capture a food
item. At higher velocities, 10.8 to 19.8 cm/s, schools of fry sometimes
held position relative to the shore or bottom while facing the current, and
an individual would typically deviate up, down, or to the sides no more
than one-third of its body length to capture oncoming food. At still
higher velocities, 19.9 to 24.4 cm/s, fry in schools often held a constant
position relative to shore or bottom but did not feed. Fry that appeared
to be in visual contact with the shore or bottom avoided currents above
24.4 cm/s unless frightened *232*.
COMMENTS ON LARVAE ENVIRONMENTAL ASSOC_ -
SALINITY:
It has been shown that some developing pink salmon eggs and alevins can be
adversely affected when exposed to some high intertidal salinities.*12*
DISSOLVED OXYGEN:
Environment Associations - 8 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
DO levels exceeding 6.0 mg/l are required for successful
development of pink salmon eggs and alevins. Oxygen consumption generally
increases as embryo development progresses, and DO generally decreases in
an area supporting large numbers of eggs or alevins. Low DO concentrations
may result in a variety of fry abnormalities. During the later part of
incubation, reduced DO can cause premature hatching.*12*
TURBIDITY
Sedimentation causes high mortality to eggs and alevin by reducing water
interchange in the redd *232*.
INSTREAM FLOW
Sufficient water velocity and depth are needed to allow proper intragravel
water movement (apparent velocity) so that dissolved oxygen is transported
to eggs and alevin and in turn metabolic wastes are removed *232*.
COMMENTS ON EGG ENVIRONMENTAL ASSOC_ -
The greatest natural mortality of pink salmon occurs during the early life
stages. In streams, less than 25% of eggs have been found by some to
survive from the time of spawning to the time of emergence from the gravel.
The causes of death of the eggs were listed as 1) digging in the redds by
other females, 2) low oxygen supply because of low stream flows or
impairment of water circulation within the streambed, 3) dislodgement of
eggs by floods, 4) freezing of eggs during periods of severe and prolonged
cold, and 5) predation by other fish *232*.
WATER TEMPERATURE:
Egg hatching rates are influenced by water temperature. Abnormally warm or
cold water can accelerate or depress developmental rates and cause
premature or delayed fry emergence. Laboratory tests have shown that eggs
require at least 4.5 degrees C water tempertures from the time the egg is
deposited in the redd through the gastrula stage of development.
Thereafter, the embryos can tolerate water temperatures to 0 degrees C if
the water does not freeze *232*.
Pink salmon eggs tolerate long periods of low temperature,
provided the initial temperature was above 6.0 C when embryogenesis began
and initial development of the embryo progressed to a stage that was
tolerant of colder water.*12*
Freezing of eggs during periods of severe and prolonged cold is listed as
one of five principle causes of death of eggs *232*.
DISSOLVED OXYGEN:
Dissolved oxygen (DO) is supplied to developing eggs and alevins within the
redd by intragravel flow. Dissolved oxygen level within the redd is
influenced by the dissolved oxygen in the stream, the rate of intragravel
water flow, and the biological demand for oxygen in the immediate area.
For incubation of salmonid eggs, concentrations at or near saturation with
temporary reductions to levels no lower than 5.0 mg/l are optimal.
However, DO levels exceeding 6.0 mg/l are required for successful
development of pink salmon eggs and alevins. Oxygen consumption generally
increases as embryo development progresses, and DO generally decreases in
an area supporting large numbers of eggs or alevins. Low DO concentrations
may result in a variety of fry abnormalities. During the later part of
incubation, reduced DO can cause premature hatching.*12*
For successful development of pink salmon eggs and alevins, the D.O. level
Environment Associations - 9 (DRAFT) - Environment Associations
Species salmon, pink
Species Id M010005
Date 26 AUG 96
should exceed 6.0 mg/l. Dissolved oxygen levels below 6.0 mg/l apparently
cause premature emergence, decreased size, and low survival *232*.
SUBSTRATE:
Eggs and developing alevins are influenced by the substrate. Productive
pink salmon streams generally contained less than 5.0% by volume of fine
sediments (<0.8 mm), whereas less productive streams had 15.0% or more
fines in the substrate.*12*
Eggs may be suffocated by the increased deposition of fine sediment and
adults may suffer from impaired oxygen transport, decline in nutritional
intake, and physical damage to the gill filaments by abrasion.*12*
The gravel over fertilized eggs reduces the disturbance caused by ice and
floods. It also protects the eggs from sunlight and predation by other
fish and aquatic insects *232*.
Egg and alevin development is influenced by substrate composition because
increased amounts of small material (fines) can reduce intragravel water
flow. Productive pink salmon streams generally contained fines (0.833 mm
diameter) contributing less than 5% of the volume of the substrate. Less
productive streams were characterized by 15% or more fines in the substrate
*232*.
TURBIDITY
Sedimentation causes high mortality to eggs and alevin by reducing water
interchange in the redd. If 15 to 20% of the intragravel spaces become
filled with sediment, salmonoid eggs have suffered significant (upwards of
85%) mortality *232*.
INSTREAM FLOW
Sufficient water velocity and depth are needed to allow proper intragravel
water movement (apparent velocity) so that dissolved oxygen is transported
to eggs and alevin and in turn metabolic wastes are removed *232*.
Depth at redds has ranged from 0.1 to 1.32 m, with preferred depths ranging
from 0.39 to 0.70 m *232*.
The amount of time required for eggs to hatch is dependent upon many
interrelated factors, including 1) dissolved oxygen, 2) water temperature,
3) apparent velocity in gravel, 4) biological oxygen demand, 5) substrate
size (limited by percentage of small fine material), 6) channel gradient,
7) channel configuration, 8) water depth, 9) surface water discharge and
velocity, 10) permeability, 11) porosity, and 12) light. Generally
speaking, factors 4 through 12 influence or regulate the key factors 1, 2,
and 3 *232*.
Environment Associations - 10 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
LIFE HISTORY
PHYSICAL DESCRIPTION:
Dorsal fin 10-15 rays; adipose small, slender, fleshy; anal 13-17 rays,
pelvics 10 rays, abdominal, with a free-tipped fleshy appendage above
insertion; pectorals 15 rays. Cycloid scales small, 150 to 205 on lateral
line, which easily distinguishes pink salmon from other species of salmon.
Gill rakers 26 to 34 on first gill arch. Body elongate and somewhat
laterally compressed.
Identification aids: Tail (caudal fin) moderatley forked. Numerous large,
black oval spots on upper sides and back and all of caudal fin. Upper jaw
reaches beyond posterior margin of orbit. Males on spawning migration
develop a prominent high hump immediately behind the head. Juveniles have
no parr marks, are blue to greenish along back and silvery on sides.
Distinguishable from other salmon by small scales *12*.
REPRODUCTION:
Pink salmon have a 2-year life cycle, which is so invariable that fish
running in odd-numbered calendar years are effectively isolated from
even-year fish so that no gene flow occurs between them. It is the simplest
and least varied life history of any salmon. Usual age at maturity is 2
years; however, 3-year-old specimens have been discovered on occasion.
The salmon return to their stream of origin to spawn in the fall when the
water temperature ranges from 8 to 14 degrees, and usually enter the river
on high water freshets. Some pink salmon spawn several miles upstream from
saltwater in a few river systems, but spawning generally takes place either
in freshwater close to the sea or in the intertidal zones. Pink salmon are
considered the most specialized of the salmon in the genus Oncorhynchus
because they are the least dependent on freshwater, regularly spawning in
the intertidal areas.
Males are larger than females. In general, larger fish, predominantly
males, enter the streams first. Runs may be alternately large and small in
consecutive years. Spawning usually occurs in late August through early
October in much of the range. The female digs a depression in the gravel on
the stream bottom in an area averaging 0.6 to 0.9 m in width, and in water
with an average depth of 0.15-0.53 m and velocity of 21-100 cm/s. The tail
is used to force water down on the gravel to remove fine sediments. A
dominant male guards the female during the digging process, attacking
competitors or intruders.
Once the nest (redd) is dug, the female drops into the middle of the deepest
part with a dominant male, and the deposition of eggs and milt occurs. Up
to six males have been recorded spawning with a single female. Researchers
have observed that, compared to larger males, smaller males showed less
spawning activity and performed more movements within the spawning ground.
After a brief milling, the spawning procedure is repeated upstream from the
nest, and the new diggings cover the eggs in the previously dug redd. The
female stays in the area, protecting her redds from other digging females.
When densities of spawners are high, nests are sometimes superimposed upon
one another and the total number of eggs surviving is reduced.
Mature female pink salmon contain between 1,500 and 1,900 eggs. Fecundity
is related positively to size *12*.
INCUBATION PERIOD/EMERGENCE:
Life History - 1 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
The eggs are large (about 6 mm in diameter) and orange-red. Both extragravel
and intragravel chemical and physical (including hydraulic) factors control
the success of egg survival. Water percolating through the gravel provides
oxygen. During the incubation period, subtantial mortality in redds may
result from freezing, flow fluctuations, dewatering, oxygen reduction,
predation, and microbial infestation. In some instances, the total egg
mortality may be as high as 75% to 90%.
The length of the incubation period is dependent on water temperature.
Under natural conditions in British Columbia, eggs hatch from late December
to late February. Once hatched, the alevins remain in the gravel for
several weeks while the yolk sac is absorbed and incorporated into the body.
Swimming fry emerge from the gravel in British Columbia streams as late
February, but peak emergence in most localities occurs during April or May
*12*.
The amount of time required for eggs to hatch is dependent upon many
interrelated factors, including 1) dissolved oxygen, 2) water temperature,
3) apparent velocity in gravel, 4) biological oxygen demand, 5) substrate
size, 6) channel gradient, 7) channel configuration, 8) water depth, 9)
surface water discharge and velocity, 10) permeability, 11) porosity, and
12) light. Generally speaking, factors 4 through 12 influence or regulate
the key factors 1, 2, and 3. Egg development requires from 61 to about 130
days, depending largely on temperature *232*.
FREQUENCY OF BREEDING:
As with all Pacific salmon, the spawning cycle is terminal. Both male and
female die after spawning *232*.
BEHAVIOR:
Pink salmon migrate to the sea soon after emerging from the gravel and spend
most of their lives in saltwater. Fry were abundant in marsh area tidal
channels of the Fraser River Estuary from March to June, with peak numbers
occurring in April and early May. Unlike chinook and chum salmon fry which
reside temporarily in the marsh before migrating into the Pacific Ocean,
pink salmon fry appear to be only transient residents of the estuarine
marsh area as they make their rapid and active migrations downstream. The
fry swim at the surface, creating ripples during their downstream migration
when cruising speeds of 0.6 ft/s are reached at temperatures of 6 to 7
degrees C.
Downstream migrations usually begin at night. Researchers reported that
migrations rarely commenced before the incident light intensity had fallen
below 0.1 foot candle at about 8:30 to 8:45 p.m., with a peak migration
between 9:00 and 10:30 p.m., and nearly no movement by 12:30 a.m. A strong
light avoidance reaction is shown initially by individual fry, but schooling
fry acclimate to the light in about 15 min and no longer avoid it.
Fry migrating to saltwater usually do not feed, but if the distance is
great, they may feed on larval insects. Both the distance traveled by the
fish and the constancy of direction are greater for large schools than for
small ones. The behavior of fry in large schools appears to be more orderly
and precise than in small schools.
Early hatchery fry migrate downstream about 35 days ahead of late hatchery
fry and about 55 days ahead of wild fry in British Columbia. Later
migrating fry have considerably higher marine survival than early migrating
fry, possibly because low water temperatures encountered by early migrating
Life History - 2 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
fry may slow their growth in the estuary and make them more vulnerable to
predators.
After leaving freshwater, the young tend to remain close inshore during
their first summer.
Migration in the sea is saltatory, with short periods of active migration
interspersed with longer periods when the fry do not migrate. Theories for
the control of marine migration include movement toward higher salinities
and the use of tidal flow and food gradients. The fish begin moving
offshore in late summer, in a manner that appears to be gradual or
irregular, and leave the young-of-the-year at a distance of 6-12 mi from the
nearest land in the fall.
After spending about 18 months at sea, adults return to the spawning streams
in predictable and highly segregated even-numbered-year and
odd-numbered-year runs. Salmon spawning migrations are thought to be guided
by environmental cues such as olfaction, currents, temperature, and
salinity, as well as by celestial navigation or magnetic orientation, but
the exact cause of the migrations is variable. The rate of straying is much
higher in pink salmon than in other species of salmon. This straying could
constitute a survival strategy that pink salmon have evolved either to
recolonize streams which have lost a year class due to environmental
catastrophe or to ensure that all fish headed for an uninhabitable stream
are not eradicated. This straying mechanism could have evolved with the
normal tendency of pink salmon to spawn in small, environmentally unstable
streams *12*.
LIMITING FACTORS:
The greatest natural mortality of pink salmon occurs during the early life
stages. In streams, less than 25% of eggs have been found by some to
survive from the time of spawning to the time of emergence from the gravel.
The causes of death of the eggs were listed as 1) digging in the redds by
other females, 2) low oxygen supply because of low stream flows or
impairment of water circulation within the streambed, 3) dislodgement of
eggs by floods, 4) freezing of eggs during periods of severe and prolonged
cold, and 5) predation by other fish *232*.
Competition and predation can have significant effects on the pink salmon
populations. Young pink salmon fry are preyed upon by a variety of stream
fishes, including Dolly Varden (Salvelinus malma), cutthroat trout (Salmo
clarki), rainbow trout (Salmo gairdneri), young coho salmon (Oncorhynchus
kisutch), northern squawfish (Ptychocheilus oregonensis), and sculpins
(Cottus spp.). Kingfishers, mergansers, other predaceous birds, and mammals
also probably account for some amount of predation. Infestations of leeches
on eggs and fry can also significantly increase mortality. Predation by and
competition with juvenile coho salmon was considered the main contributor to
early sea mortality in pink salmon according to researchers. Yearling Coho
apparently prey selectively on young pink salmon, even in the presence of
chum salmon that are both significantly smaller and more abundant than the
pink salmon. Early sea mortality can also be associated with predation by
certain species such as herring. Adults at sea are preyed upon by humans,
marine mammals, and, to a lesser extent, large fishes. Upon returning to
the rivers, pink salmon are preyed on by bears and humans *12*.
POPULATION ATTRIBUTES:
Life History - 3 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
When the fry hatch and leave the substrate, they range from 3.2 to 3.8 cm in
total length from the tip of the snout to the fork of the tail and weigh
approximately 0.3 g. The fry feed relatively little, if at all, during
their downstream migration and thus leave the streams at about this same
size.
During the first 30-day period at sea (beginning in August or September),
the fry increase in weight by a factor of 6. During their first 40 days at
sea, pink salmon grow to about 8 cm and by the following March reach a
length of about 33 cm. During the last spring and summer in the sea, growth
is rapid from about 0.5 kg up to an average weight of between 2 and 4 kg
*12*.
FEEDING BEHAVIOR:
Pink salmon select their food by sight and swallow it whole. Studies using
visual observations have indicated that feeding varies with the speed of the
water current and often stops at higher velocities (19.9 to 24.4 cm/s).
In offshore marine waters, pink salmon appear to have a
vertical feeding pattern, with light intensity the major factor *232*.
Reproductive Habitat: Pink salmon spawning takes place in a variety of
locations. In some instances spawning takes place in stream mouth areas
where water levels change with the tides and where varying degrees of
salinity are experienced. In small coastal streams the upstream limit is
usually defined by a waterfall situated within a few miles of the sea. In
larger rivers without major obstructions, the end-point may be less
definite. The grounds that are intensively occupied by pink salmon tend to
have a relatively low gradient. Because of the effects of dewatering and
freezing, the amount of available habitat at the time when adult salmon are
spawning is a poor indicator of the amount of actual habitat that is
available as potential incubation habitat. Estimates of available
incubation habitat must take into account the differential effects of
dewatering and freezing in various habitat types *232*.
Reproductive Seasonality: In Alaska, pink salmon ascend freshwater streams
from June to late September, depending largely on location. Spawning takes
place in mid July in the lower Yukon but generally not until late August to
October in areas to the south *232*.
Reproductive Behavior: As with other salmon, adult pink salmon return from
the sea and move into their natal freshwater streams to spawn. There is,
however, a degree of wandering. Adults have been taken in spawning streams
as much as 643 km from their original stream. The female selects the
spawning site and digs the redd (nest) by turning on her side and thrashing
her tail up and down. The current washes loosened substrate material
downstream, and a depression up to 45.7 cm deep is formed in the river
bottom. Eggs and sperm (milt) are released simultaneously and deposited in
the redd. After egg deposition, the female moves to the upstream margin of
the redd and repeats the digging process. Dislodged substrate is washed over
the eggs. In this manner the eggs are covered and prevented from washing
away. The process is repeated many times, and the redd apprears to move
upstream. As a result of the continued digging, the redd may grow to become
0.9 m in length. A female may dig several redds and spawn with more than one
male. Males may also spawn with several females *232*.
Life History - 4 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
Age at Sexual Maturity: Unlike the other Pacific salmon, the pink salmon
matures in two years. Though rare three-year-old fish have been found, it
is probable that they are sterile *232*.
Fecundity: The number of eggs carried by pink salmon entering the spawning
area varies with the size of the female, the area, and the year. Each
female may produce as few as 800 or as many as 2,000 eggs, with the average
estimated at 1,500 to 1,900. In general, larger fish have more eggs, but
fish from small runs are said to be more fecund than those of the same size
from large populations *232*.
Frequency of Breeding: As with all Pacific salmon, the spawning cycle is
terminal. Both male and female die after spawning *232*.
Incubation of Period/Emergence: The amount of time required for eggs to
hatch is dependent upon many interrelated factors, including 1) dissolved
oxygen, 2) water temperature, 3) apparent velocity in gravel, 4) biological
oxygen demand, 5) substrate size (limited by percentage of small fine
material), 6) channel gradient, 7) channel configuration, 8) water depth, 9)
surface water discharge and velocity, 10) permeability, 11) porosity, and
12) light. Generally speaking, factors 4 through 12 influence or regulate
the key factors 1,2, and 3. Egg development requires from 61 to about 130
days, depending largely on temperature. The young hatch from late December
through February and remain in the gravel until April or May *232*.
Size of Use Areas: From studies of Columbia River tributaries, a
conservative figure for the number of pairs of salmon that can
satisfactorily utilize a given area of spawning gravel may be obtained by
dividing the area by four times the average size of the redds. The redd
area can by computed by measuring the total length of the redd (upper edge
of pit to lower edge of tailspill) and the average of several equidistant
widths *232*.
Timing of Movements and Use of Areas: Pink salmon fry emerge from the
gravel at night and begin their downstream migration to the sea. Where
known, Alaska specific timing information is contained in the salmon
distribution and abundance narratives found in this report series. During
July of 1967, small schools of pink salmon fry were observed migrating
upstream along shore through the narrows between Tikchik Lake and Nuyakuk
Lake in company with larger sockeye fry and yearlings. This behavior is
unusual for pink salmon. When the distance to the sea is short, they reach
the estuary of the stream before dawn. On longer journeys that cannot be
made in one night, the fry hide in the gravel during the day and resume
their downstream movement the next night. Fry that must migrate for several
days sometimes become daylight-adapted, in which case they school and no
longer hide during the day. After entering the estuary, the juveniles begin
feeding and move with surface currents. After about a month, the young fish
attain a length of 4 cm, then follow the salinity gradient within the
estuary, generally staying fairly close to the shore. When they reach a
length of 6 to 8 cm they move to offshore waters. After about 18 months at
sea, the adult pink salmon return to fresh water to spawn *232*.
Life History - 5 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
Migration Routes: Freshwater streams and rivers serve as downstream
migration corridors for ocean-bound juveniles and as upstream migration
pathways for spawning adults. From marine distribution data, it is evident
that pink slamon are present across the entire North Pacific Ocean from Asia
to North America, north of about 42 deg N. Tagging studies have shown that
each stock has a characteristic distribution that is similar in odd- and
even-year cycles. When combined, these studies have shown that the mass of
maturing pink salmon in the North Pacific is composed of a number of stocks,
each of which has a rather well-defined distribution that may overlap with
one or more distributions of adjacent stocks *232*.
Southeastern, Southcentral, and Southwestern (south-side of Alaska
Peninsula) stocks: The oceanic migrations of stocks of pink salmon
originating in Southeast, Southcentral, and Southwest Alaska are similar
enough to be treated as one. Generally speaking, these stocks are found in
the North Pacific and Gulf of Alaska in an area bounded on the west by about
longititude 165 deg W, on the south by latitude 42 deg N, and on the east
and north by the North American continent. Juveniles from southeast Alaska
in their first marine summer and fall move generally northwestward but
likely do not move far offshore. Juveniles from Southcentral and Southwest
Alaska in their first marine summer and fall move southwestward along the
Alaska Peninsula. Some juveniles from Southeast Alaska may move west and
join the Southcentral and Southwestern stocks in this area. Juvenile pink
salmon are distributed farther offshore in the north Gulf of Alaska than
they are off Southeast Alaska, which may indicate that offshore dispersion
begins in the northcentral Gulf of Alaska. No adequate measurements of
offshore dispersion have been made south of the Alaska Peninsula. Assumed
migrations during the late fall and winter of their first year at sea
indicate that the young pink salmon are further offshore and have begun a
general southeastward movement that probably occurs on a broad front within
the spring-summer distribution. During their second spring and summer, the
maturing fish begin a generally northward movement from the high seas
enroute to their natal streams *232*.
Southwestern (north-side Alaska Peninsula): Very little information is
available concerning pink salmon marine migrations from stocks in Western
and Southwest Alaska. No data are available on seaward migrations of the
juveniles during their first summer. From small numbers of tag returns of
maturing adults it is supposed that these stocks are found in an area
bounded on the west by 180 deg in the Bering Sea. They may also be found
south of the eastern and central Aleutian Islands south to about latitude 50
deg N and thence southeasterly to about longitude 140 deg W at latitude 48
deg N. They probably do not extend beyond 54 deg N in the North Pacific
*232*.
Natural Factors Influencing Populations: The greatest natural mortality of
pink salmon occurs during the early life stages. In streams, less than 25%
of the eggs survive from the time of spawning to the time of emergence from
the gravel; the principle causes of death of the eggs are 1) digging in the
redds by other females, 2) low oxygen supply because of low stream flows or
impairment of water circulation within the streambed, 3) dislodgement of
eggs by floods, 4) freezing of eggs during periods of severe and prolonged
cold, and 5) predation by other fish. Juveniles are preyed upon by a
Life History - 6 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
variety of fishes (e.g., cutthroat and rainbow trout, Dolly Varden, coho
salmon smolts, and sculpins), kingfisher, mergansers, and other predaceous
birds and mammals. Mortality during early sea life (first 40 days) is
fairly high at 2 to 4% per day, where predation by birds, fishes, and
various invertebrates may be an important factor in mortality at this time.
Adults at sea are preyed upon by marine mammals, Pacific and arctic lamprey,
and to a lesser extent by large fish. Sea survival rates are highly
variable and have been computed at about 2 to 22% and probably average 5%.
A study documents the die-off of prespawn adult pink salmon in Porcupine
Creek on Etolin Island in Southeast Alaska. The fishes' migration route to
spawning areas was blocked at the intertidal stream reach by low stream flow
and neap tides. Within four days, about 3,000 pink and chum salmon had
collected in a large pool in the intertidal reach of the stream. The
crowded fish lowered the dissolved oxygen level to less than 2 mg/l, and
some salmon began to die in the center of the pool *232*.
Human-related Factors Influencing Populations: 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*.
Special Considerations: Schools of adult pink salmon often frequent bays and
estuaries for days and even weeks before entering the streams. Fish tagged
at this stage still show movements away from, as well as towards, the
nearest spawning gounds. It appears that spawning populations are not
necessarily well segregated until actual entrance into the spawning streams.
Because of the two-year life cycle, returns of spawning adults are
predictable by highly segregated even-numbered year and odd-numbered year
runs. Both types of runs, or races, may use the same stream, or one or the
other may predominate in a particular river. Some streams with a dominant
run of one type have a very much smaller off-year run of the other race;
they often utilize different tributaries as spawning grounds. There may be a
significant difference in the date of return and in the length and weight of
individuals of the two races or of the same race in different spawning
rivers *232*.
LIFE HISTORY CODES -
Breeding/Spawning Season: July
Breeding/Spawning Season: August
Breeding/Spawning Season: September
Breeding/Spawning Season: October
Spawning Site: Gravel
Gestation/Incubation Period: 1-2 months
Gestation/Incubation Period: 3-4 months
Average Number of Offspring/Reproductive Effort: 1,00
Dispersion: Clumped
Periodicity: Active in day
Nest Materials: Gravel
Life History - 7 (DRAFT) - Life History
Species salmon, pink
Species Id M010005
Date 26 AUG 96
LIFE HISTORY CODES -
Mating System (Single breeding season): Promiscuity (
Average Number of Offspring/Reproductive Effort: 101-
Gestation/Incubation Period: 5-6 months
Periodicity: Active at night
REFERENCES FOR LIFE HISTORY- 12 and 232
Life History - 8 (DRAFT) - Management Practices
Species salmon, pink
Species Id M010005
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Existing Regulating harvest of species being described
Existing Other management practices [specified in comments]
Adverse Migration barriers
Adverse Construction of navigational improvements [dams, locks, etc.]
Adverse Other management practices [specified in comments]
Beneficial Controlling sedimentation
Beneficial Developing/maintaining suitable pH
Beneficial Controlling water levels
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 - 12 and 232
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 12
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 12
COMMENTS ON MANAGEMENT PRACTICES -
MANAGERIAL AUTHORITY
Within Alaska:
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-mile limit *232*.
North Pacific Management Council:
There is a Salmon Power Troll Fishery Management Plan which is federal law
and applies to marine areas between the 3-mile limit and the 200-mile limit
*232*.
International North Pacific Fisheries Commission (INPFC):
The INPFC has prepared conservation measures that limit the location, time,
and number of fishing days that designated high seas areas (beyond the
200-mile limit) may be fished by Japanese nationals and fishing vessels
*232*.
POSSIBLE IMPACTS FROM HUMAN RELATED ACTIVITIES
A summary of possible impacts from human-related activities includes the
following:
- Alteration of preferred water temperature, pH, dissolved oxygen, and
chemical composition
Management Practices - 1 (DRAFT) - Management Practices
Species salmon, pink
Species Id M010005
Date 26 AUG 96
- 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
- Human harvest *232*
SPECIAL CONSIDERATIONS
Caution must be used when extending information from one stock of pink
salmon to another stock. Environmental conditions for 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*.
THE FISHERY
Ocean fisheries are managed by a catch quota system, while fisheries in
terminal areas are managed by subtracting escapement goals from preseason
run updates. After subtraction of the ocean catches and escapement goals,
the estimated number remaining gives the total allowable harvest, which is
allocated among user groups. The Washington Department of Fisheries and the
various tribal entities have worked much more closely toward a unified
salmon management plan due to the Boldt Decision in 1974 *12*.
Management Practices - 2 (DRAFT) - References
Species salmon, pink
Species Id M010005
Date 26 AUG 96
References
12* Bonar, S., Pauley, G., Thomas, G. 1989. Species Profiles: Life
Histories and Environmental Requirements of Coastal Fishes and
Invertebrates (Pacific Northwest)--Pink Salmon. U.S. Fish and
Wildlife Service Biol. Rep. 82(11.88) pp 18.
232 * State of Alaska Department of Fish, and Game. 1986. Alaska
Habitat Management Guide: Life Histories and Habitat
Requirements of Fish and Wildlife. (ed.). Alaska Department of
Fish and Game Juneau, Alaska:763.
References - 1