(DRAFT) - Taxonomy
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
TAXONOMY
NAME - salmon, Atlantic
OTHER COMMON NAMES - ouananiche, Kennebec salmon, sebage salmon and landlocked salmon
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Vertebrata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Clupeiformes,
FAMILY AND SUBFAMILY - Salmonidae,
GENUS AND SUBGENUS - Salmo,
SPECIES AND SSP - salar,
SCIENTIFIC NAME - Salmo salar
AUTHORITY - Linnaeus
TAXONOMY REFERENCES - 38 and 231
COMMENTS ON TAXONOMY -
Other common names: Ouananiche, Kennebec salmon, landlocked salmon, Sebage
salmon.
French common names: Saumon atlantic, saumon d'eau douce, bratan.
Life stage names: Parr (freshwater juvenile), smolt (juvenile migrating to
sea), grilse (adult returning to freshwater to spawn after one year at sea),
bright salmon (adult returning after two or more years), kelt or black
salmon (a postspawning or spent adult).
Taxonomy - 1 (DRAFT) - Status
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
International treaty
REFERENCES FOR STATUS - 38
COMMENTS ON STATUS -
Once relatively widespread, this species is now restricted to several rivers
of New England where dams, pollution, and fishing have excessively reduced
reproductive potential. During the egg, larval, and parr stages, this
salmon is especially vulnerable to the consequences of coastal
development projects; therefore knowledge of the life history and
environmental requirements of this species is essential for decisions that
will assure its continued existance and enhancement.
In the late 1800's dams and water pollution destroyed the Atlantic salmon in
U.S. waters except for a few streams in Maine. Populations in some Canadian
streams were diminished by 1860. At this time Maine had the only remaining
profitable commercial Atlantic salmon fishery in the U.S. About 70% of the
catch was from the Penobscot River, but by 1896, only 40 fish were landed
there. Since then, the U.S. has had no significant commercial catch of
salmon. This is a biased value since commercial fishing is illegal in the
U.S. A small catch of salmon has been reported for Massachusetts and Maine,
where sale of salmon caught with sport gear is permitted. Sport catches
provide a better measure of the Atlantic salmon fishery.
Collapse of the Lake Ontario Atlantic salmon fishery prompted a series of
legislative acts in Canada to control the commercial fisheries. A 1973 ban
on drift-net fishing off Newfoundland and on commercial fishing in New
Brunswick (both lifted in 1981) was a response to world reductions of
Atlantic salmon catch.
In the late 1960's and early 1970's, tagged salmon from both sides of the
Atlantic were caught in a common area off the west coast of Greenland and
off the Faroe Islands. Because Atlantic salmon swim close to the surface,
they are easy to catch in drift and set gill nets. To reverse the trend of
increased catches on the high seas, quotas were set. The Faroe Island
fishery quota was set at 750 metric tons in 1982, and 625 metric tons in
1983. The quota for Greenland was set at 1,250 metric tons for these years.
The Convention for the Conservation of Salmon in the North Atlantic Ocean
Treaty, approved February 1982, prohibited salmon fishing within 12 mi of
another country's coastline, with the exception of west Greenland, where
fishing only beyond 40 mi was permitted, and the Faroe Islands where fishing
was permitted only beyond 200 mi.
Based on catch by anglers and in traps for hatcheries the total return in
Maine in 1982 was 4,685 adult Atlantic salmon, compared to 4,134 in 1981.
Records are incomplete, however, for some of the smaller rivers. Of the
1982 run, 4,161 were from the Penobscot River. In southern New England in
1982, 46 salmon returned to the Merrimack River, 70 to the Connecticutt
river (down from the 530 in 1981) and 38 (an estimate of 50) in the
Pawcatuck River in Rhode Island, the first time adult Atlantic salmon have
returned to this river in nearly 200 years.
Status - 1 (DRAFT) - Status
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
As a sport fish, Atlantic salmon are rated as one of the best. They are
hard fighters and high jumpers and are considered a prestigious game fish by
many anglers. In 1982, Penobscot anglers reported catching 914 salmon
(about 1500 were actually caught) during 13,384 angler days on one short
section of 115 acres of the river. The average angler fished 38 hr to catch
one fish *38*.
Status - 2 (DRAFT) - Distribution
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 38
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine OW0 V 1
Marine OW0 V 1
Estuarine AB. L 0
Lacustrine AB. H 0
Lacustrine AB. H 0
Riverine SB1 H 0
Riverine SB1 L 0
Riverine SB1 H 0
Riverine SB1 L 0
Riverine SB1 H 0
Riverine SB1 L 0
REFERENCES FOR NWI - 38
Habitat Associations - 1 (DRAFT) - Food Habits
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 38
LIFESTAGE FOOD FOOD PART
Juvenile Insects Larva stage
Juvenile Insects Adult stage
Juvenile Molluscs Not Specified
Juvenile Annelids Not Specified
Juvenile Clupeiformes Not Specified
Juvenile Crustaceans Not Specified
Adult Clupeiformes Not Specified
Adult Crustaceans Not Specified
Larva Insects Larva stage
Larva Annelids Not Specified
Larva Molluscs Not Specified
REFERENCES FOR GENERAL FOOD - 38
REFERENCES FOR ADULT FOOD - 38
REFERENCES FOR JUVENILE FOOD - 38
REFERENCES FOR LARVAE FOOD - 38
COMMENTS ON FOOD -
After hatching, the yolk-sac larvae remain buried in the gravel absorbing
their yolk sacs for nourishment for about 6 weeks. When the yolk sacs are
fully absorbed, the fry begin to forage for food.
Young Atlantic salmon usually remain relatively stationary in the stream and
feed on invertebrate drift. Their diet consists chiefly of larvae of
mayflies and stoneflies, chironomids, caddisflies and blackflies, aquatic
annelids and mollusks. Larger juveniles feed on aquatic insects and
terrestrial insects that fall into the water.
In the sea, smolt and larger salmon eat herring, lance, alewives, capelin,
smelt, small mackerel, cod, haddock, and crustaceans. Salmon eat very
little or nothing after returning to freshwater from the sea, but some will
attack an angler's lure *38*.
COMMENTS ON JUVENILE FOOD -
Young Atlantic salmon usually remain relatively stationary in the stream and
feed on invertebrate drift. Their diet consists chiefly of larvae of
mayflies and stoneflies, chironomids, caddisflies and blackflies, aquatic
annelids and mollusks. Larger juveniles feed on aquatic insects and
terrestrial insects that fall into the water.
In the sea, smolt and larger salmon eat herring, lance, alewives, capelin,
smelt, small mackerel, cod, haddock, and crustaceans. Salmon eat very
little or nothing after returning to freshwater from the sea, but some will
attack an angler's lure *38*.
Food Habits - 1 (DRAFT) - Food Habits
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
COMMENTS ON LARVAE FOOD -
After hatching, the yolk-sac larvae remain buried in the gravel absorbing
their yolk acs for nourishment for about 6 weeks. When the yolk sacs are
fully absorbed, the fry begin to forage for food *38*.
Food Habits - 2 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
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
E Water Temperature: Below 15 degrees C
E Dissolved Oxygen: Moderate [5-7 mg/l] oxygen concentrations
E Water pH: Between 6.5-8.5
L Water Temperature: Below 15 degrees C
L Water pH: Between 6.5-8.5
L Water Depth Preference: Less than 1 ft.
L
L Bottom Type [Aquatic]: Pebble
L Turbidity: Specified in Comments
J Aquatic Features: Riffles
J Water Temperature: Between 15-21 degrees C
J Dissolved Oxygen: Specified in Comments
J Water pH: Between 5.0-6.5
J Water Depth Preference: Specified in Comments
J Water Velocity [Instream Flow Group Increments]: Specified in Comments
J
J Bottom Type [Aquatic]: Pebble
J Bottom Type [Aquatic]: Gravel
A Aquatic Features: Riffles
A Coastal Features: Specified in Comments
A Water Temperature: Specified in Comments
A Dissolved Oxygen: Specified in Comments
A Water pH: Between 5.0-6.5
A Water Depth Preference: Specified in Comments
A Water Velocity [Instream Flow Group Increments]: Specified in Comments
A Bottom Type [Aquatic]: Pebble
A Bottom Type [Aquatic]: Gravel
A
J Aquatic Features: Riffles
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR FEEDING ADULT ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR RESTING ADULT ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR BREEDING ADULT ENVIRONMENTAL ASSOC_ - 38
Environment Associations - 1 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
REFERENCES FOR FEEDING JUVENILE ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR RESTING JUVENILE ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR FEEDING LARVAE ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR RESTING LARVAE ENVIRONMENTAL ASSOC_ - 38
REFERENCES FOR EGG ENVIRONMENTAL ASSOC_ - 38
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
TEMPERATURE: Water temperature is the key factor in the delineation of the
geographical range of the Atlantic salmon. They require cool temperatures
at all stages of their life history. Spawning occurs between 4.4 and 10
deg C. The optimum temperature of egg fertilization and incubation is
about 6 deg C, although development may occur at slower rates at
temperatures as low as 0.5 deg C. Temperatures of 7 deg C are tolerated,
whereas temperatures above 12 deg C increase egg mortality. Temperatures
between 8 and 12 deg C may indirectly increase mortality, due to a higher
incidence of fungal infection. Newly hatched Atlantic salmon alevins
select the lowest temperatures available. About 250 degree days after
hatching the alevins select a temperature of 14 deg C.
Growth and production of juveniles are optimum at water temperatures of 15
to 19 deg C, although they will tolerate temperatures up to 27 deg C, at
which point they move to colder water. The lethal temperature for juveniles
is about 32 deg C. A minimum of 100 days in which the temperature exceeds 6
deg C is needed for the growing season. Growth was optimum at 16.6 deg C.
Adults grow in ocean temperatures as low as 2 deg C. Mortality can be
expected at water temperatures higher than 28 deg C. Temperatures of 20 to
27 deg C reduce resistance to disease and are therefore indirectly lethal.
At water temperatures above 20 deg C adults are rarely caught by angling.
DISSOLVED OXYGEN: For optimum growth and development, dissolved oxygen
concentrations should be at or near saturation. Good development requires
at least 6 mg/l. Streams with dissolved oxygen concentrations below 5 mg/l
are not usually inhabited by salmon. Migrating adult salmon require a
minimum of 5 mg/l for exposure less than 6 hr and 6 mg/l for exposure more
than 6 hr.
The respiration of adult Atlantic salmon is depressed at oxygen
concentrations below 4.5-5.0 mg/l. At concentrations from 1.5-1.7 mg/l,
most fish die from a lack of oxygen. Lethal concentrations for juveneile
Atlantic salmon are about 1.1 mg/l for age 0+ parr and 2.3 mg/l for age 1+
parr tested at the same water temperatures as the adults. Embryos require
even higher oxygen levels of 6-7 mg/l. Oxygen consumption differs among
fish of different sex, age, and weight. The rate of oxygen consumption in
adults decreases with age and body weight.
pH: Fluctuations in pH of water are important in the freshwater
environment of the Atlantic salmon. Tolerance to low pH varies among
different life stages and ages. High mortality of eggs and alevins has
been attributed to low pH, which is characteristic of snowmelt and heavy
rain falls. Eggs develop normally at pH 6.6-6.8. A pH of 4.0-5.5 delays
or prevents hatching, yet returning these eggs to 6.6 induces hatching.
The lower lethal pH for embryos is about 3.5 during early cleavage and
about 3.1 just before hatching.
Environment Associations - 2 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
Death by low pH is attributed to dysfunction of ionregulation,
asphyxiation, and elevation of metal concentrations. Exposure to low pH
causes edema between outer gill lamellar cells and other gill tissue,
disrupting respiration and excretion. A pH of 5.0 or lower affects eggs by
degradation of the enzymes responsilble for movement of the embryo within
the egg, without which hatching is impossible. At pH 5.0-5.5 reproduction
fails. Alevins subjected to low pH at 7 days and parr at 28 days after
hatching had a lower lethal limit of about 4.0. Rivers in Nova Scotia with
a mean pH less than 4.7 have lost salmon runs; between 4.7 and 5.0 runs
declined; and above 5.0 runs were unaffected. Juveniles in these Nova
Scotia streams were most numerous at mean annual pH above 5.4, much
reduced between 4.7 and 5.0, and absent below 4.7.
DEPTH AND VELOCITY: The optimum stream habitat for spawning is a gravel
tail of a pool with a hydraulic head produced by a riffle or a steeper
gradient below the pool. The gravel has an average area of 3.8 m sqr.
Water depth over a redd averages 0.4 m in Maine rivers and 0.2 m in New
Brunswick rivers. Water velocity at 12 cm above the substrate averaged 49
cm/sec in Maine, and at 2.5 cm above the substrate, 52 cm/sec in New
Brunswick. The average water depth in a Maine salmon stream was 38 cm
(range 17-76) with a water velocity of 53 cm/sec, measured 12 cm above the
substrate.
Atlantic salmon fry less than 60 mm long tend to stay in depths less than
20 cm. The fry may not be able to compete with older fry in deeper waters
because of predation and/or chasing, or they may simply prefer shallower
water. Competition for space among fish of different ages may be the
critical regulating factor affecting the survival of first year (0+) fry.
In one study, the preferred fry habitat had a mean depth of 25 cm (range
9-39 cm). The depth of 62 sites where salmon fry were found in New
Brunswick streams ranged from 10 to 31 cm.
Parr, 1+ year and older, seem to prefer waters 10-40 cm deep. Mean depth
of preferrred areas in New England streams was 29 cm, and 10-15 cm in
Canadian streams.
First-year fish (age 0+) prefer water velocities of 50-65 cm/sec.
Preferred habitat of 0+ fish had a mean velocity of 14 cm/sec (range 1.8-32
cm/sec), whereas 1+ parr were in habitat with a mean of velocity of 20
cm/sec (range 14-32). Stream gradients that salmon prefer range from 2 to
12 m/km.
Resting pools for upstream migrants are important as temporary refuge from
swift currents. Large boulders and other stream obstructions provide
eddies and slack water in which adult salmon may rest.
LIGHT: At surface illuminations between 0.4 and 160 foot-candles (fc),
salmon were photopositive, while at illuminations above 300 fc they were
photonegative when the lighted area had an unbroken substrate. With
submerged cover in the lighted area, the salmon were photopositive. The
amount of shade over a steam indirectly affects the survival of salmon by
preventing solar radiation from warming the water above the upper lethal
temperature.
SALINITY: Tolerance of Atlantic salmon to sudden changes in salinity
differs among its life stages. Smolts greater than 120 mm can survive an
instantaneous change from freshwater (0.1 ppt) to 100% seawater (30 ppt)
for 84 hr, and are completely tolerant when introduced into 27 ppt
seawater. Parr 7 to 100 mm can tolerate 30 ppt seawater for 10 hr after
direct introduction, and survive indefinately in waters of 22 ppt seawater.
Environment Associations - 3 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
Parr 30-40 mm are able to survive for only 2.5 hr in 30 ppt seawater but
are tolerant of about 18 ppt seawater. Fry 15-20 mm perish within 2 hr
after sudden introduction into 30 ppt seawater but can tolerate a level of
8 ppt indefinitely. Six-week-old alevins survive for only 0.5 hr in 30 ppt
seawater but survive well in salinities near 20 ppt. One-week-old alevins,
however, are able to survive up to 9 hr in 100% seawater, even though 3% is
optimal. The epithelium of these alevins may be able to maintain some
degree of impermeability, which is lacking in somewhat older fish, and may
account for the longer survival of younger fish at high salinities.
Atlantic salmon parr, though adapted for life in freshwater, can readily
survive within a wide salinity gradient from 0 to 20 ppt. Instantaneous
growth rates and food conversion efficiencies of salmon in different
salinities were similar.
SUBSTRATE, SEDIMENT, AND TURBIDITY: The spawning habitat has a particle
size composition consisting of 0%-3% fine sand (0.06-0.50 mm); 10%-15%
coarse sand (0.5-2.2 mm); 40%-50% pebble (2.2-22 mm); and 40%-60% cobble
(22-256 mm). First-year fish (0+) prefer a substrate of gravel 1.6-6.4 cm
in diameter while parr of age 1+ prefer a boulder and rubble substrate
greater than 26 cm in diameter. Bottom sedimentation plays an important
role in the survival and distribution of juvenile salmon. Spaces between
pebbles and cobble are used as shelter by fry and parr. Deposition of
sediments that clog these spaces decrease survival of salmon fry and parr.
Turbidities in excess of 1150 standard units, caused by autumn freshets,
did not injure or kill salmon fry and parr. Turbid water in spring may
protect migrating smolts from predation *38*.
COMMENTS ON RESTING ADULT ENVIRONMENTAL ASSOC_ -
Adults grow in ocean temperatures as low as 2 deg C. Mortality can be
expected at water temperatures higher than 28 deg C. Temperatures of 20 to
27 deg C reduce resistance to disease and are therefore indirectly lethal.
At water temperatures above 20 deg C adults are rarely caught by angling.
DISSOLVED OXYGEN: For optimum growth and development, dissolved oxygen
concentrations should be at or near saturation. Good development requires
at least 6 mg/l. Streams with dissolved oxygen concentrations below 5 mg/l
are not usually inhabited by salmon. Migrating adult salmon require a
minimum of 5 mg/l for exposure less than 6 hr and 6 mg/l for exposure more
than 6 hr. The respiration of adult Atlantic salmon is depressed at oxygen
concentrations below 4.5-5.0 mg/l. At concentrations from 1.5-1.7 mg/l,
most fish die from a lack of oxygen.
pH: Tolerance to low pH varies among different life stages of the Atlantic
salmon. Rivers in Nova Scotia with a mean pH less than 4.7 have lost
salmon runs; between 4.7 and 5.0 runs declined; and above 5.0 runs were
unaffected.
WATER VELOCITY: Stream gradients that salmon prefer range from 2 to 12
m/km. Resting pools for upstream migrants are important as temporary
refuge from swift currents. Large boulders and other stream obstructions
provide eddies and slack water in which adult salmon may rest.
LIGHT: At surface illuminations between 0.4 and 160 foot-candles (fc),
salmon were photopositive, while at illuminations above 300 fc they were
photonegative when the lighted area had an unbroken substrate. With
submerged cover in the lighted area, the salmon were photopositive. The
amount of shade over a steam indirectly affects the survival of salmon by
Environment Associations - 4 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
preventing solar radiation from warming the water above the upper lethal
temperature.
SALINITY: Tolerance of Atlantic salmon to sudden changes in salinity
differs among lifestages. Smolts greater than 120 mm can survive an
instantaneous change from freshwater (0.1 ppt) to 100% seawater (30 ppt)
for 84 hr, and are completely tolerant when introduced into 27 ppt
seawater.
TURBIDITY: Turbid water in spring may protect migrating smolts from
predation *38*.
COMMENTS ON BREEDING ADULT ENVIRONMENTAL ASSOC_ -
TEMPERATURE: Atlantic salmon spawn at temperatures between 4.4 and 10 deg
C. The optimum temperature of egg fertilization and incubation is about 6
deg C, although development may occur at slower rates at temperatures as
low as 0.5 deg C.
pH: At pH 5.0-5.5 reproduction fails.
DEPTH AND VELOCITY: The optimum stream habitat for spawning is a gravel
tail of a pool with a hydraulic head produced by a riffle or steeper
gradient below the pool. The gravel has an average area of 3.8 m sqr.
SUBSTRATE: The spawning habitat has a particle size composition consisting
of 0%-3% fine sand (0.06-0.50 mm); 10%-15% coarse sand (0.5-2.2 mm);
40%-50% pebble (2.2-22 mm); and 40%-60% cobble (22-256) *38*.
COMMENTS ON RESTING JUVENILE ENVIRONMENTAL ASSOC_ -
TEMPERATURE: Growth and production of juveniles are optimum at water
temperatures of 15-19 deg C, although they will tolerate temperatures up to
27 deg C, at which point they move to colder water. The lethal temperature
for juveniles is about 32 deg C.
DISSOLVED OXYGEN: For optimum growth and development, dissolved oxygen
concentrations should be at or near saturation. Lethal concentrations for
juvenilve Atlantic salmon are about 1.1 mg/l for age 0+ parr and 2.3 mg/l
for age 1+ parr tested at the same water temperatures as the adults.
pH: Juveniles in Nova Scotia streams were most numerous at mean annual pH
above 5.4, much reduced between 4.7 and 5.0, and absent below 4.7.
DEPTH AND VELOCITY: Parr, 1+ year and older, seem to prefer waters 10-40
cm deep. Mean depth of preferred areas in New England streams was 29 cm,
and 10-15 cm in Canadian streams. First-year fish (age 0+) prefer water
velocities of 50-65 cm/sec. Preferred habitat of 0+ fish had a mean
velocity of 14 cm/sec (range 1.8-32 cm/sec), whereas 1+ parr were in
habitat with a mean velocity of 20 cm/sec (range 14-32).
SALINITY: Atlantic salmon parr, though adapted for life in freshwater, can
readily survive within a wide salinity gradient from 0 to 20 ppt.
SUBSTRATE, SEDIMENT, AND TURBIDITY: First-year fish (0+) prefer a
substrate of gravel 1.6-6.4 cm in diameter while parr of age 1+ prefer a
boulder and rubble substrate greater than 26 cm in diameter. Bottom
sedimentation plays an important role in the survival and distribution of
juvenile salmon. Spaces between pebbles and cobble are used as shelter by
fry and parr. Deposition of sediments that clog these spaces decrease
survival of salmon fry and parr. Turbidities in excess of 1150 standard
units, caused by autumn freshets, did not injure or kill salmon fry and
parr *38*.
Environment Associations - 5 (DRAFT) - Environment Associations
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
COMMENTS ON RESTING LARVAE ENVIRONMENTAL ASSOC_ -
TEMPERATURE: Newly hatched Atlantic salmon alevins select the lowest
temperatures available. About 250 degree days after hatching the alevins
select a temperature of 14 deg C.
pH: High alevin mortality has been attributed to low pH. Alevins
subjected to low pH at 7 days had a lower lethal limit of about 4.0.
DEPTH AND VELOCITY: Atlantic salmon fry less than 60 mm long tend to stay
in depths less than 20 cm. The fry may not be able to compete with older
parr in deeper waters because of predation and/or chasing, or they may
simply prefer shallower water. Competition for space among fish of
different ages may be the critical regulating factor affecting the survival
of first-year (0+) fry. In one study, the preferred fry habitat had a mean
depth of 25 cm (range 9-39 cm). The depth of 62 sites where salmon fry
were found in New Brunswick streams ranged from 10 to 31 cm.
SALINITY: Fry 15-20 mm perish within 2 hr after sudden introduction into
30 ppt seawater but can tolerate a level of 8 ppt indefinately.
Six-week-old alevins survive for only 0.5 hr in 30 ppt seawater but survive
well in salinities near 20 ppt. One-week-old alevins, however, are able to
survive up to 9 hr in 100% seawater, even though 3% is optimal *38*.
COMMENTS ON EGG ENVIRONMENTAL ASSOC_ -
TEMPERATURE: The optimum temperature of egg fertilization and incubation
is about 6 deg C, although development may occur at slower rates at
temperatures as low as 0.5 deg C. Temperatures of 7 deg C are tolerated,
whereas temperatures above 12 deg C increase egg mortality.
DISSOLVED OXYGEN: Embryos require oxygen levels of 6-7 mg/l.
pH: High mortality of eggs has been attributed to low pH, which is
characteristic of snowmelt and heavy rains. Eggs develop normally at pH
6.6-6.8. A pH of 4.0-5.5 delays or prevents hatching, yet returning these
eggs to pH 6.6 induced hatching. The lower lethal pH for embryos is about
3.5 during early cleavage and about 3.1 just before hatching. A pH of 5.0
or lower affects eggs by degradation of the enzymes responsible for
movement of the embryo within the egg, without which hatching is
impossible *38*.
Environment Associations - 6 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
LIFE HISTORY
MORPHOLOGY/IDENTIFICATION AIDS: Body elongate, somewhat compressed
laterally, greatest body depth at dorsal fin origin or slightly posterior to
dorsal fin, 18% to 22% of the total length. Head length about equal to or
slightly greater than body depth, 20% to 23% of the total length, but most
variable during modifications of head structure during spawning. Eye
moderate, 14% to 19% of head length (variable depending on growth rate);
snout rounded, its length greater than eye diameter for fish over 305 mm
long; mouth terminal, large, maxillary extending posteriorly to posterior
margin of pupil when 152 mm long, and seldom to posterior margin of eye
except on mature males, which develop a pronounced hook or kype on lower
jaw. Well-developed teeth on upper and lower jaws (premaxillary, maxillary,
dentary); few teeth in a single row on shaft of vomer and palatines, on
tongue in two rows; no hyoid teeth. Total gill raker count, 15-20.
Branchiostegal rays usually 11-12 (rarely 10 or 13). Fins: adipose present
posterior to dorsal, dorsal 10-12; anal, 8-11; ventral, 9-10, with a
distinct pelvic axillary process; pectoral, 14-15. Caudal with shallow
fork. Scales cycloid, 109-121 in lateral line, 10-13 from posterior edge of
adipose base to lateral line; lateral line decurved anteriorly, straight
posteriorly. Pyloric caeca, 40-74. Vertebrae, 58-61.
Pigmentation: Color varies with age, environment, and life stage. Small
parr have 8-11 pigmented bars alternating with a single row of red spots
along the lateral line on each side. Migrating smolts and adults at sea are
silvery on the sides and belly, but the adults have brown, green, or blue
coloration on the back and numerous black spots, usually X-shaped, scattered
across the body, more numerous above the lateral line. A few of these spots
are also located on the head. Landlocked adults have more numerous and
larger spots than anadromous salmon (called bright salmon when first
entering fresh water). At spawning, pectoral and caudal fins become
blackish and both sexes take on a bronze to purple coloration and may
acquire reddish spots on the head and body. After spawning, the surviving
adults (kelts) are dark colored.
Distinctions: Dark spots on a light background distinguish Atlantic salmon
from light spotted chars (brook trout and arctic char), which have light
spots on a dark background. Atlantic salmon also have larger scales, and
have teeth on the shaft of the vomer. They may be distinguished from
rainbow trout by the absence of serial rows of black spots on caudal fin and
from brown trout by the shorter maxillary, narrower peduncle, lack of red on
the adipose, and larger scales. Species of introduced Pacific salmon are
distinguished by the larger number of anal fin rays, 12-19, whereas the
Atlantic salmon has 8-11.
LIFE HISTORY: Spawning: Atlantic salmon spawn during the period of
mid-October to mid-Novermber in gravel areas of freshwater streams.
Spawning sites are located at the downstream end of the riffles with water
percolation through the gravel or at upwellings of groundwater. Redds are
constructed by the females using her caudal fin in a fanning motion. A redd
consists of several depressions or pits excavated from the stream bottom.
Water temperatures during spawning usually range between 4.4 deg and 5.6 deg
C. The male aligns himself with the female and fertilizes the eggs as they
Life History - 1 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
are deposited into each pit. Some male parr become sexually mature and take
an active part in fertilizing eggs. The female then covers the eggs with
about 10-25 cm of the gravel excavated while building another pit just
upstream. This process is repeated until spawning is completed.
Fecundity and eggs: Fecundity depends largely on body size. For example,
anadromous Atlantic salmon produce more eggs than the landlocked form
because its females are larger. A rule of thumb is that anadromous females
produce 1,500 to 1,800 eggs/kg. Females weighing about 5 kg produced about
1,800 eggs/kg. The following formula was used to estimate the number of
eggs produced by fish with different body lengths in another study:
Log10 N = 2.69 log10 L - 0.15
Eggs are spherical, 5-7 mm in diameter, and pale orange or amber. The eggs
are slightly adhesive initially and stick to the substrate in the pit until
they are covered with gravel. The incubation period varies with stream
temperature. In Maine the eggs hatch in April or early May after 175 to 195
days under normal winter conditions. An incubation of 110 days at 3.9 deg C
probably is for hatchery eggs.
Eggs size is influenced by the age, size, and physiological condition of the
female. Egg size is also determined by the length of time the female lives
in the ocean, the time of spawning, and the position of the egg in the
ovaries. Average egg weight is 164 mg. The rate of embryo development is
not affected by egg size, but embryo size is larger in larger eggs and the
resulting larvae have higher survival. Egg size increases with fecundity
and size of females.
Larvae and juveniles: After hatching, the eleutheroembryos (alevin or
yolk-sac larvae), about 15 mm long, remain buried in the gravel absorbing
their yolk sacs for nourishment for about 6 weeks. When the yolk sacs are
fully absorbed, the 25 mm fry begin to forage for food in the substrate,
and then emerge from the substrate. In a Maine stream, between May 12 and
28 emergence was always at night. In New Brunswick streams, peak emergence
and dispersal were between June 12 and 23. After emergence, fry disperse
and immediately establish territories. The competition for territory may
limit the number of fish in the population. The young salmon are also
displaced downstream by water flow. By late summer population density of
parr is usually less than 50/100 m sqr, but may be as much as 370/100 m sqr
in New Brunswick.
Of the eggs deposited, only about 5% result in production of fry. Mortality
rates are also high during emergence and dispersion. Egg-to-fry survival in
Newfoundland streams was influenced by winter temperatures and change in
water levels described in the equation:
Nfry/Neggs = 68.07 + 1.89X - 0.005Y
where X = the lowest mean monthly temperature (deg C) and Y = the difference
between the November mean discharge and the lowest winter mean monthly
discharge (1/sec). Egg-to-parr survival in Cove Brook, Maine, was 10%.
Year class strength of smolts was related to egg deposition in three New
Brunswick streams with the equation:
ln Y = 1.29 ln X - 8.014
where X is the number of eggs (thousands) and Y is the number of smolts of
that year class.
On reaching a length of about 40 mm during the first summer, young salmon
are called parr or fingerlings. These juvenile salmon are found
Life History - 2 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
predominently in riffle sections of the stream. Young parr are more
numerous in rapidly flowing water during the day and early evening. At
night they rest on the bottom in the quieter waters. Older parr are
residents of the deeper pools in streams. They defend territories and
attack other parr entering the defended zone. This practice allocates space
and food to insure adequate growth and reduce predation by other species.
Parr frequently move upstream or downstream, perhaps as a result of
aggressive interactions, and some parr may migrate to tributaries previously
unpopulated with salmon. In New Brunswick streams abundance is usually less
than 15/100 m sqr but in a few streams may be as high as 62/100 m sqr.
In the fall, many male parr become sexually mature, ensuring a mixture of
breeding stock. Parr remain in the stream until they are 125-150 mm length,
which may take up to 2-3 years; they remain in streams until they are 180
mm long and 4-8 years old in the Ungava Bay region of Canada. Parr that
fail to reach the critical length by spring or early summer in any one year
do not transform into smolts until the following spring, regardless of
subsequent growth. If smolts are prevented from seaward migration they
again become parr and lose their ability to survive in salt water.
Smolts and sea migrants: The smolt is the next stage in the life history of
the Atlantic salmon. In Maine, about 80% of the juveniles spend 2 years and
20% spend 3 years. Thirty-eight percent of the parr in the Polett River,
New Brunswick, survived to smoltification (survival from egg to smolt was
1.1%). Also reported was 3.6% and 3.2% survival from egg to smolt in two
Newfoundland streams. Survival of 5% from fry to the smolt was observed in
Cove Brook, Maine. Egg-to-smolt survival in the Miramichi River, New
Brunswick, was analyzed and it was concluded that percentage survival was
inversely related to the initial number of eggs deposited. Absolute numbers
of smolts produced, of course, were higher in streams receiving heavy egg
deposition, up to about 300 eggs/100 m sqr, above which density-dependent
mortality compensated for increased numbers.
After the parr reach 125 to 150 mm, the parr marks disappear and deposition
of guanine in the skin creates a silvery pigmentation. The tail lengthens
and becomes more deeply forked. Schooling behavior replaces territorial
behavior.
During the spring, rises in water levels due to freshets and water
temperature increases +4.5 to +5.5 deg C induce downstream smolt migration
in the Thurso River, Scotland. A rise in temperature to 5 deg C reportedly
triggered downstream migration in the Penobscot River, Maine. Smolts
expressed full migratory behavior at 9-10 deg C. Peak movements were at
dawn and dusk. In riffles and low-velocity stream sections, smolts orient
downstream; but in swift currents, they orient upstream. Migrating smolts
passively drift in the main current of the stream away from the shoreline.
On reaching the estuary, smolts swim seaward during the flood tide.
Impoundments delay or restrict migration. It was found that the entire
journey from freshwater to seawater took less than 48 hr over a distance of
57 km. Smolt movement in estuaries is dependant on the characteristics of
the estuary. Movement in deep water is parallel to current direction, while
in shallow water sun compass orientation is dominant.
Mortality due to freefall over dams and natural falls is likely if the
velocity of the fish exceeds 15 m/sec on impact with the water. This
velocity is reached by smolts falling a vertical distance of 27 m where
discharge is 0.4 m cubed/sec (grilse, 18 m, and kelts, 16 m). Smolts may
Life History - 3 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
withstand freefall of up to 90 m.
Sea life and homeward migration: Once in the sea, Atlantic salmon travel to
distant feeding grounds. Most American and southern European salmon migrate
to the Davis Straits between Labrador and Greenland. Salmon from the Baltic
Sea and British Isles migrate to the coast of the Faroe Islands. The
postsmolts swim within 3 m of the ocean surface at a rate of up to 50
km/day. One possible explanation for their navigating such long distances
on target is their ability to detect changes in the earth's electromagnetic
geoelectric fields caused by the passage of ocean currents through the
fields.
After feeding at sea, most Atlantic salmon return to their natal stream to
spawn. Return to the home stream may be aided by detection of olfactory
stimuli from the stream that initiate behavioral response mediated by memory
of the homestream odor. One hypothesis for homeward migration is that
during the downstream migration, smolts release a pheromone, creating an
odor trail specific for each population from the home stream to the feeding
ground. Adults may follow this trail to return to their home stream.
Some adults (grilse) return to their home stream after 1 year at sea,
weighing 1-3 kg. Other adults (bright salmon) return after 2 or 3 years at
sea and weigh 3-9 kg, although much larger salmon have been recorded. Fish
returning to Maine rivers usually have spent 2 years at sea. At sea the
returning adults swim at rates of 0.08-0.68 m/sec.
Salmon congregate in estuaries, bays, and river mouths before migrating
upstream. Migration often coincides with freshets or other sustained
increases in water flow. Freshets are less important in spring when water
is colder and the flow higher than in summer or in autumn. Salmon are
rheotactic and require a minimum stream velocity of 0.3-0.6 m/sec to
continue movement upstream. The rate of progress upstream against an
average flow velocity of 0.5 m/sec (35 km/day) was reported to be 4.3
km/day.
Adult salmon do not feed in freshwater. As males mature, their heads become
elongate and the lower jaws become enlarged and hooked, forming kypes. The
females choose the spawning site. In contrast to Pacific salmon, Atlantic
salmon do not die after spawning. Many spent fish (kelts) survive the
winter in freshwater and resume feeding. Apparently mortality is high when
the kelts enter saltwater. Fish that survive and migrate to oceanic feeding
ground may become repeat spawners. Landlocked or permanently freshwater
salmon move from the lake where they feed to a tributary stream where they
spawn.
GROWTH CHARACTERISTICS: Growth of the Atlantic salmon is influenced by both
genetic and environmental factors. Embryo size and weight are determined by
egg size, which is influenced by the age, size, and physiological condition
of the female. Egg diameter increases with the age of the fish and the
length of time the fish spend in ocean feeding. Egg size also varies in
individual females, depending on the position of the eggs in the ovary.
Growth of fry and parr in freshwater is relatively slow. Salmon fry obtain
maximum growth in July with little or no growth after September. It may
take 2-3 years to reach a 125-150 mm fork length in streams in New England,
and 4-8 years to reach 180 mm in Ungava Bay. In productive streams in
Maine 1+ parr may reach 150-175 mm, and 2+ parr of 210 mm are occasionally
seen.
Life History - 4 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
Normal growth of parr occurs at water temperatures of 15-19 deg C.
Population density also affects growth and survival. Growth rates are
usually greater where densities are least. From a study on the Pollett
River, New Brunswick, it was concluded that average smolt production in an
ideal salmon stream should not exceed 6 smolts/100 m sqr. This calculation
was based on a spawning intensity of 170 eggs/100 m sqr. The 2.4 eggs/m sqr
often cited by management biologists as optimum, may be an "arbitrary"
figure and that optimal egg deposition could be considerably higher in
productive salmon rivers. Ideal numbers of eggs needed in streams of
differing survival and adult escapement, ranging from 23 eggs/m sqr with low
escapement and high survival to 591 eggs/m sqr under high escapement and low
survival were calculated.
Photoperiod also influences growth. Sexually mature male and female
Atlantic salmon exposed to a light:dark (LD) ratio of 20:4 grew faster than
those exposed to a natural photoperiod (nLD) or LD 6:18. Sexually maturing
male parr, however, grew slower in LD 20:4 than did immature fish exposed to
the same photoperiod. When exposed to LD 6:18 or nLD, maturing males
ripened earlier.
Size is one of the most important factors determining the age at which
Atlantic salmon become smolts. Fish that become smolts in one year mature
and spawn for the first time later than those that smoltify in 2 or 3 years.
The mean age of the female's first spawning varies over the salmon's range
in North America, decreasing from Maine to Ungava. The mean age of the
first spawning among individuals is positively correlated with growth rates
at sea.
Growth in the sea is faster than in freshwater. In 1 year at sea a salmon
may grow 1-3 kg and in 2 years, 3-7 kg. Average weights of anadromous
salmon returning to various streams range from 2 and 9 kg although rates
have been recorded up to 38 kg. Commercially caught salmon average 4.5 kg.
Adult landlocked salmon average 1-2 kg.
The growth of Atlantic salmon is reflected in scales. When about 30 mm
long, the fry begin to grow scales, first along the lateral line at the
central and posterior parts of the body. During rapid growth, broad bands
form on the scale, similar to growth rings on a tree. The bands are used to
determine the age and growth of individuals. Because growth differs in
freshwater and the ocean, the time that an individual has spent in
freshwater and in the ocean can be estimated. During upstream migration,
the salmon partially absorbs its scales; thus, the number of spawning runs
made by an older fish can also be determined.
Production (P) of juvenile Atlantic salmon can be estimated from the mean
biomass (B) for all year-classes present in a typical Welsh stream with the
following formula:
P = -2.5 B^0.91
The exponent actually ranged from 0.73 to 1.24, and the coefficient ranged
from -1.91 to -3.05. The higher values appeared in the spring and summer.
The size of 0+ salmon in a Scottish river depended on the growing season's
length, which is determined by emergence time, degree days above 0 deg C,
and population density (numbers/m sqr). The relationship of fork length
(FL) to population density (N) and degree days (D) is determined by the
following equation:
FL = 17.152 - 2.800N + 0.0194D
No significant relationship between length of 1+ salmon and their population
density could be established. The annual production rates for salmon ranged
Life History - 5 (DRAFT) - Life History
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
from 5.5 g/m sqr to 12.1 g/m sqr and averaged 8.9 g/m sqr. Production in
the second year of a particular year class could not be statistically
related to production of that year class in its first year of life. Smolt
production in streams ranged from about 1 to 10 smolts/100 m sqr.
ECOLOGICAL ROLE: Food habits: Young Atlantic salmon usually remain
relatively stationary in the stream and feed on invertebrate drift. Their
diet consists chiefly of larvae of mayflies and stoneflies, chironomids,
caddisflies and blackflies, aquatic annelids and mollusks. Larger juveniles
feed on aquatic insects and terrestrial insects that fall into the water.
In the sea, smolt and larger salmon eat herring, lance, alewives, capelin,
smelt, small mackerel, cod, haddock, and crustaceans. Salmon eat very
little or nothing after returning to freshwater from the sea, but some will
attack an angler's lure.
Predation: Salmon are eaten by a variety of predators in freshwater and at
sea. Young salmon are eaten by eels, northern pike, brook trout, larger
salmon, and other predaceous fishes; gulls, mergansers, cormorants, herons,
and kingfishers; and backswimmers and leeches. At sea major predators are
pollock, tuna, swordfish, sharks, otters, and seals *38*.
REFERENCES FOR LIFE HISTORY- 38
Life History - 6 (DRAFT) - Management Practices
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Existing Regulating harvest of species being described
Existing Other management practices [specified in comments]
Beneficial Controlling pollution [thermal, chemical, physical]
Adverse Shoreline modification/development
Adverse Migration barriers
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 38
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 38
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 38
COMMENTS ON MANAGEMENT PRACTICES -
Commercial fishing of Atlantic salmon is illegal in the U.S.
The species was an important commercial fish in the British Isles and
medieval Europe. They were mentioned in the Magna Carta and were an
important source of protein in the American colonies. Settlers found rivers
teeming with them. Reports of their capture with pitchforks and their use
as fertilizers were documented. In the late 1800's dams and water pollution
destroyed the Atlantic salmon in U.S. waters except for a few streams in
Maine. Populations in some Canadian streams were diminished by 1860. At
this time Maine had the only remaining profitable commercial Atlantic salmon
fishery in the U.S. About 70% of the catch was from the Penobscot River,
but by 1896, only 40 fish were landed there. Since then, the U.S. has had
no significant commercial catch of salmon. This is a biased value since
commercial fishing is illegal in the U.S. A small catch of salmon has been
reported for Massachusetts and Maine, where sale of salmon caught with sport
gear is permitted. Sport catch provides a better measure of the Atlantic
salmon fishery.
Collapse of the Lake Ontario Atlantic salmon fishery prompted a series of
legislative acts in Canada, to control the commercial fisheries. A 1973 ban
on drift-net fishing off Newfoundland and on commercial fishing in New
Brunswick (both lifted in 1981) was a response to world reductions of
Atlantic salmon catch.
In the late 1960's and early 1970's, tagged salmon from both sides of the
Atlantic were caught in a common area off the west coast of Greenland and
off the Faroe Islands. Because Atlantic salmon swim close to the surface,
they are easy to catch in drift and set gill nets. To reverse the trend of
increased catches on the high seas, quotas were set. The Faroe Island
fishery quota was set at 750 metric tons in 1982, and 625 metric tons in
1983. The quota for Greenland was set at 1,250 metric tons for these years.
The Convention for the Conservation of salmon in the North Atlantic Ocean
Treaty, approved February 1982, prohibited salmon fishing within 12 mi of
another country's coastline, with the exception of west Greenland, where
fishing only beyond 40 mi was permitted, and the Faroe Islands where fishing
was permitted only beyond 200 mi *38*.
Restoration efforts on most rivers are guided by formal plans having
long-range objectives. Restoration activities may include various
Management Practices - 1 (DRAFT) - Management Practices
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
combinations of five basic techniques: 1. Research: Conduct varied research
projects to gain additional information on the biology of the salmon. 2.
Cultural: The hatching, rearing, and stocking of juvenile and adult salmon.
3. Fish Passage: Provide salmon access to sections of a river upstream from
obstructions and, where necessary, a safe means for downstream migrating
adults and juveniles to by-pass hazards. 4. Habitat Enhancement: Habitat
manipulation to enhance wild salmon production capability. 5. Conservation
Measures: Regulations to control the commercial and recreational harvests of
salmon in home waters and the high seas.*158*
Management Practices - 2 (DRAFT) - References
Species salmon, Atlantic
Species Id M010017
Date 26 AUG 96
References
38* Danie, D.S., J.G. Trial, and J.G. Stanley. 1984. Species profiles:
life histories and environmental requirements of coastal fishes and
invertebrates (North Atlantic) -- Atlantic salmon. U.S. Fish Wildl.
Serv. FWS.OBS-82/11.22. U.S. Army Corps of Engineers, TR EL-82-4.
19 pp.
*158* New England Fishery Management Council. 1987. Fishery Management
Plan for Atlantic Salmon. U.S. Fish and Wildlife Service Biol.
Rep. pp 64.
231 * National Oceanographic Data Center. 1984. National
Oceanographic Data Center Taxonomic Code; Volume 2: Alphabetical
(Scientific Name Order) Listing. 2 (ed.). National Oceanographic
Data Center Washington, DC:374.
References - 1