Bull Trout

              Bull trout are members of the char subgroup
of the salmon family (salmonids), which also
includes the Dolly Varden, lake trout and
Arctic char. Bull trout living in streams
grow to about four pounds while those in
lake environments can weigh more than
20 pounds.
Biologists distinguish char from other
salmonids such as trout and salmon by the
absence of teeth in the roof of the mouth; the
presence of light colored spots on a dark
background (trout and salmon have dark
spots on a lighter background); the absence
of spots on the dorsal fin; their smaller
scales; and differences in skeletal structure.
Char species such as bull trout live farther
north than any other group of freshwater
fish except Alaskan blackfish and are well
adapted for life in very cold water.
Bull trout and Dolly Varden look very similar
and once were considered the same species.
However, taxonomic research has identified
them as different species. Both have small,
pale yellow to crimson spots on a darker
background, which ranges from olive green
to brown above, fading to white on the belly.
Spawning adults develop varying amounts of
red on the belly. Both species also exhibit
differences in size, body characteristics,
coloration and behavior across their range.
Bull trout are larger than Dolly Varden, with
a relatively longer and broader head. Bull
trout are mainly an inland species, while
Dolly Varden are more common in coastal
areas. In Washington State, both species are
present in the Puget Sound area.
Historically bull trout occurred throughout
the Columbia River Basin; east to western
Montana; south to the Jarbidge River in
northern Nevada, the Klamath Basin in
Oregon, and the McCloud River in
California; and north to Alberta, British
Columbia, and possibly southeastern Alaska.
Today bull trout are found primarily in
upper tributary streams and several lake
and reservoir systems; they have been
eliminated from the main stems of most
large rivers. The main populations
remaining in the lower 48 states are in
Montana, Idaho, Oregon and Washington
with a small population in northern Nevada.
Bull trout are now extinct in northern
California.
Small bull trout eat terrestrial and aquatic
insects but shift to preying on other fish as
they grow larger. Large bull trout primarily
prey on fish such as whitefish, sculpins and
other trout.
Bull trout reach sexual maturity between
four and seven years of age and are known
to live as long as twelve years. They spawn
in the fall after temperatures drop below
48° Fahrenheit, in streams with cold,
unpolluted water, clean gravel and cobble
substrate, and gentle stream slopes. Many
spawning areas are associated with cold
water springs or areas where stream flow is
influenced by groundwater. Bull trout eggs
require a long incubation period compared to
other salmon and trout (four to five months),
hatching in late winter or early spring. Fry
remain in the stream bed for up to three
weeks before emerging. Juvenile fish retain
their fondness for the stream bottom and are
often found at or near it.
Bull Trout
Salvelinus confluentus
U.S. Fish & Wildlife Service
Some bull trout live near areas where they
were hatched. Others migrate from streams
to lakes, reservoirs or salt water a few weeks
after emerging from their gravel nests.
Migratory bull trout grow to be bigger than
resident stream fish.
Some bull trout live near areas where they
were hatched. Others migrate from streams
to lakes or reservoirs (or, in the case of
coastal populations, salt water) a few weeks
after emerging from the gravel. Migratory
bull trout grow to be bigger than resident
stream fish. However, lakes and reservoirs
are not good spawning habitat, so migratory
bull trout may swim considerable distances
to spawn when habitat conditions allow.
The ability to migrate or move within stream
systems is important for healthy bull trout
populations to maintain local fish numbers,
facilitate gene flow among subpopulations
and reestablish extirpated groups.
Bull trout are vulnerable to many of the
same threats that have reduced salmon
populations in the Snake River Basin. They
are more sensitive to increased water
temperatures, poor water quality and low
flow conditions than many other salmonids.
Past and continuing land management
activities such as timber harvest and
livestock grazing have degraded stream
habitat, especially those along larger river
systems and stream areas located in valley
bottoms, to the point where bull trout can no
longer survive or reproduce successfully. In
many watersheds, remaining bull trout are
small, resident fish isolated in headwater
streams.
Brook trout, introduced as a sport fish
throughout much of the bull trout’s range,
easily interbreed with bull trout, producing
sterile offspring. Non-native brook trout also
reproduce earlier and at a higher rate than
bull trout, often supplanting bull trout
populations. Interbreeding between bull
trout and brown trout and lake trout is a
problem in some areas. Dams and other
in-stream structures also affect bull trout by
blocking migration routes, altering water
temperatures and killing fish as they pass
through and over dams, or are trapped in
irrigation and other diversion structures.
In June 1998, the U.S. Fish and Wildlife
Service listed the bull trout in the
Columbia River and Klamath River as
threatened under the Endangered Species
Act of 1973. An endangered species is
considered in danger of extinction
throughout all or a significant portion of its
range. A threatened species is considered
likely to become endangered within the
foreseeable future.
For listing purposes the range of bull trout
was broken into distinctive population
segments. Bull trout occur in widespread,
but fragmented habitats and have several
life history patterns. In addition, threats are
diverse and the population status and trends
vary considerably throughout the range.
By examining distinct population segments,
bull trout in most need of federal protection
become a listing priority.
Many of the actions intended to protect
other declining salmonids may also help bull
trout. Stream and habitat protection and
restoration, reduction of siltation from roads
and other erosion sites, and modification of
land management practices to improve
water quality and temperature are all
important. Several state fish and wildlife
agencies have enacted regulations reducing
or prohibiting bull trout harvest. Several
states also have drafted or adopted
conservation plans to help bull trout
populations recover.
Besides the measures outlined above, a
strong commitment by private citizens,
industry, state, federal, and tribal groups to
change, reduce or eliminate activities that
degrade streams and rivers will be
necessary to truly recover many species of
native fish. Much bull trout habitat in
mainstream rivers and streams is privately
owned, making conservation activities on
private lands a key element to restoring
aquatic habitat and recovering native fish
populations. In some areas, reducing the
potential for hybridization of bull trout with
non-native fish species would enhance bull
trout survival and recovery.
U.S. Fish & Wildlife Service
1 800/344 WILD
http://www.fws.gov
November 1998
Bull trout spawn in the fall after
temperatures drop below 48° Fahrenheit,
in streams with cold, unpolluted water,
clean gravel and cobble substrate and
gentle stream slopes. Bull trout eggs
require a long incubation period
compared to other salmon and trout
(four to five months), hatching in late
winter or early spring. Fry remain in
the stream bed for up to three weeks
before emerging.