Family Cyprinidae - Minnows or Carps
Order Cypriniformes - Minnows, Suckers, Loaches
Risk Status
Official status
The Chiselmouth is currently on British Columbia's Blue
List (CDC = G5 S3S4). COSEWIC
has assigned a Not At Risk status as of 2003, but is listed as Sensitive
by SARA.
Historical facts
Chiselmouths made their way through the Columbia and Lower Fraser
rivers as glaciers melted. During deglaciation, periodic connections
between the Fraser River headwaters and the Columbia River system
allowed chiselmouths, and other fish species, to spread beyond the
confines of the Columbia River basin in BC.
Distinguishing features
Chiselmouths are unique among BC’s fishes in that adults
have a cartilage lips on the upper and lower jaws which are used
to scrape algae from rocks. They have a blunt nose, and the jaws
almost appear straight, unlike any other fish in this province.
Chiselmouths also have minute scales, narrow tail base, and large
forked tail, and in this respect, look like fast-water suckers from
the south-west United States. They are drab minnows, with a brown
back and lighter sides and belly; the sides may be peppered with
fine black spots. Young fish may have a pale spot at the base of
the tail, and adults sometimes have orange tint to the base of the
pectoral and pelvic fins.
Distribution
British Columbia
The only known Chiselmouth populations in Canada are in the Euchiniko
and Nazko Rivers, and Nicola Lake of the Fraser River system. They
also occur in Missezula, Wolfe, Skaha, Galagher, and Tugulnuit lakes,
and the Similkameen River of the Okanagan portion of the Columbia
River, and Windemere Lake of the Kootenay portion of the Columbia
River basin.
North America
Chiselmouths are found in Nevada, Idaho, Oregon and Washington,
and fossil chiselmouths (Acrocheilus xestes) are known
from the Pliocene and Pleistocene of Idaho.
Habitat
Canadian Chiselmouths are more common in lakes than rivers, but
occasionally are collected in streams. In Washington they are known
to inhabit larger, warm, sluggish streams, commonly over pebbles,
cobble, rocks, and rarely over silt and sand. Lake dwelling Chiselmouths
migrate into rivers or tributary streams to spawn. In the Similkameen
River in BC, Chiselmouths have been captured alongside Northern
Pikeminnows, Redside Shiners, Torrent Sculpins, a variety of suckers,
Longnose Dace, Leopard Dace, and “Umatilla” dace.
Why is it of Concern?
The main reason for concern regarding the status of Chiselmouths
is that we know so little about this species in British Columbia.
Most of what we know about the species in Canada comes from the
M.Sc. thesis of G. Moodie (1966). Since then, hydroelectric developments,
urbanization, recreational use of our waterways, and agricultural,
and industrial developments in southern British Columbia all have
increased in intensity. This increased pressure on aquatic habitats,
and its impact on the ecology of the region’s waterways must
have an effect on populations of Chiselmouths.
Even game fishes introduced for anglers impact native species either
directly as a result of increased predation and disease transmission,
or indirectly through competition for limited food resources. Given
that we know so little about this species in BC, it is difficult
to predict how Chiselmouth populations will react to modern pressures.
It also is of concern given that its global range is restricted
only to the Pacific Northwest.
Biology
Breeding
Chiselmouths spawn in late June to early July at water temperatures
of 17°C or warmer, but no one has seen the actual spawning act.
Eggs seem to be scattered over clean rocks, gravel and cobble; females
average around 6200 eggs each. Newly hatched young are about 8 mm
long, and they absorb their yolk by the time they reach 15 mm length.
In BC, male chiselmouths probably mature at 3 years of age, and
females mature at 3-4 years. Chiselmouths may reach 225 mm and 6
years of age. In Washington they are known to reach at least 8 years
of age and 304 mm; females up to 304 mm can carry around 12,000
eggs. Unfortunately, there is disagreement between age estimates
of fishes determined by scales and otoliths, and so after 5 years
of age, longevity estimates are not reliable.
Behaviour
Very little is known about Chiselmouth behaviour. In Washington,
Chiselmouths in a variety of sizes and age-classes have been observed
together, but it is unknown whether they school together or all
congregate where food is abundant. Feeding individuals dart forward
to scrape algae off rocks, but young Chiselmouths and adults also
are known to take aquatic insects from open water and from the surface.
Diet or Growing requirements
Stomachs of adult Chiselmouths usually contain diatoms and filamentous
algae, caddisflies, and midge larvae, where as young Chiselmouths
(up to 10 cm total length) take cladocera (water-fleas) and insects,
either from the water column, or from the surface. They also ingest
detritus, but his may be accidentally eaten along with algae.
Predators
Predators of Chiselmouths may include mergansers, loons, herons,
as well as a range of piscivorous (fish-eating) fishes such as trout,
charr, sculpins, and Northern Pikeminnows. Unfortunately, nothing
is known about how these algae-eating minnows fit into the ecology
of our rivers, but they serve as a link between primary productivity
(algae growth) and aquatic predators.
Sources for more
information
Related On-line Sites to Visit
References
Coad, B. E. 1995. Encyclopedia of Canadian Fishes. Canadian Museum
of Nature and Canadian Sport Fishing Productions, Inc. Ottawa, Ontario.
928 p.
Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister,
and J. R. Stauffer. 1980. Atlas Of North American Freshwater Fishes.
Publication No. 1980-12, North Carolina Biological Survey. North
Carolina State Museum Of Natural History. 854 p.
McPhail, J.D., and R. Carveth. 1994. Field Key to the Freshwater
Fishes of British Columbia. Resources Inventory Committee, Government
Publications Centre, Victoria, British Columbia. 239 p.
Scott, W. B., and E. J. Crossman. 1973. Freshwater Fishes of Canada.
Fisheries Research Board of Canada, Bulletin 184. Ottawa, Ontario.
966 p.
Wydoski, R. S., and R. R. Whitney. 2003. Inland Fishes of Washington.
University of Washington Press, Seattle, U.S.A. 320 p.
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