Species Fact Sheet Warner sucker Catostomus warnerensis
STATUS: THREATENED CRITICAL HABITAT: DESIGNATED
Warner sucker potentially occurs in these Oregon counties: Lake (Map may reflect historical as well as recent sightings)
The Warner sucker was federally listed as threatened in September
1985. A recovery plan was published in April 1998.
The Warner sucker is a slender-bodied species that attains a
maximum fork length of 456 millimeters (18 inches). Pigmentation
of sexually mature adults can be striking. The dorsal two-thirds
of the head and body are blanketed with dark pigment, which borders
creamy white lower sides and belly. During spawning season, males
have a brilliant red lateral band along the midline of the body.
Females are lighter.
Historic Status and Current
The probable historic range of the Warner sucker includes the
main Warner lakes (Hart, Crump, and Pelican), ephemeral lakes,
sloughs, and lower-gradient streams. Historically abundant and
widely distributed in the basin, the Warner sucker still maintains
sizable numbers in a few habitats. It is still known to occur
in most lakes, sloughs, and potholes, except during drought years.
Stream resident populations are found in Honey and Twentymile
creeks, and in Deep Creek below Deep Creek Falls. In most habitats
the Warner sucker is rare, although aggregations of spawning adults
or young-of-the-year may be encountered.
Drought in the late 1980s and early 1990s dried most lake and
slough habitats and basin-wide surveys conducted from 1993 to 1997,
after the lakes had refilled, documented the recolonization of
these habitats by native and non-native fish. Prior to the drought,
the lake population of suckers was comprised of only large older
individuals indicating a lack of successful reproduction or recruitment
to lake habitats. During the same time, non-native piscivorous
(fish-eating) fishes [crappie (Pomoxis sp.) and brown bullhead
comprised approximately 87 percent of the fish fauna in the Warner
lakes. Following the drought, recolonization by native fishes,
including the Warner sucker, was found to occur at a much faster
rate than for non-native fishes. Surveys in 1997 indicated that
native fish [Warner suckers, tui chubs (Gila bicolor
redband trout (Oncorhynchus mykiss ssp.)] comprised approximately
80 percent of the total catch. Information collected from 1993
to 1997 suggests that the drought may have had a significantly greater
impact on non-native fishes as compared to the native species
that evolved under fluctuating environmental conditions. However,
over time it is anticipated that the number of crappie and brown
bullhead will increase significantly to levels observed prior
to the drying of lake habitat in 1992.
Larvae are found in shallow backwater pools or on stream margins
where there is no current, often among or near macrophytes (aquatic
plants). Young-of-the-year use deep still pools, but also move
into faster flowing areas near the heads of pools. Adults use
stretches of stream where the gradient is low enough to allow
the formation of long, >50 meters (>164 feet), pools. These pools
tend to have undercut banks, large beds of aquatic macrophytes, root
wads or boulders, a vertical temperature differential of at least
2º C (35.6º F), a maximum depth >1.5 meters (>5 feet),
and over-hanging vegetation.
Reasons for Decline
General stream channel and watershed degradation from livestock
grazing has caused hydrologic impacts to sucker habitat. In addition,
numerous small, agricultural diversion dams on creeks reduce stream
flows and prevent migrations of adults and young. In lake habitats,
non-native brown bullhead and crappie are abundant. The crappie
and brown bullhead are presumed predators on young suckers.
Completed actions include fencing of streams to restore riparian
vegetation, acquisition of ephemeral lake habitat, and construction
of a fishway for passage over a diversion dam on Twentymile Creek.
The Bureau of Land Management and the USDA Forest Service have altered
their grazing and forest management practices to improve habitat
for Warner suckers. Additional conservation measures needed include
improving stream habitat and watershed conditions throughout the
Warner Basin, re-establishing migration corridors, screening irrigation
diversions, controlling exotic fishes, and maintaining adequate
water supplies for fish.
Many of these conservation actions will also benefit native redband
trout and tui chubs. Continuing drought through 1992 dried "permanent"
lakes, such as Hart and Crump, for the first time since the 1930s,
highlighting the importance of preserving diverse habitat types.
Allen, C.S., A. Atkins, M.A. Stern, and A.V. Munhall. 1994. Status
and recolonization rates of the Warner sucker (Catostomus
and other fishes in the Warner Lakes in SE Oregon 1994. U.S. Bureau
of Land Management, U.S. Fish and Wildlife Service and the Oregon
Natural Heritage Program of The Nature Conservancy.
Allen, C.S., K.E. Hartzell, M.A. Stern, A.V. Munhall. 1995. Status
of the Warner sucker (Catostomus warnerensis) and other fishes
in the Warner Basin in SE Oregon. U.S. Bureau of Land Management
and the Oregon Natural Heritage Program of The Nature Conservancy.
Allen, C., K. Hartzell, and M. Stern. 1996. Warner sucker progress
report - 1996 findings. Unpublished report to Bureau of Land Management.
Fish and Wildlife Service. 1985. Determination that the Warner
sucker is a threatened species and designation of its critical habitat.
White, R. K., T. L. Ramsey, M. A. Stern & A. V. Munhall.
1991. Salvage operations and investigations of the range and stream
habitat characteristics of the Warner sucker, (Catostomus
during spring and summer 1991. Oregon Natural Heritage Program,
Portland. 44 pp.
Williams, J. E., M. A. Stern, A. V. Munhall & G. A. Anderson.
1990. Conservation status of threatened fishes in Warner Basin,
Oregon. Great Basin Naturalist. 50:243-248.
Williams, J.E. Threatened Fishes of the World: Catostomus
warnerensis, Snyder, 1908 (Catostomidae). Environmental Biology