The Warner sucker Catostomus warnerensis is endemic to the Warner Basin of
southeastern Oregon and northeastern Nevada. The species was formerly
abundant and widely distributed in the basin. The species has declined
in the last century due to stream habitat degradation and fragmentation,
blockage of migratory corridors, entrainment in water diversions, and
predation by non-native fishes. This species was listed by the U.S.
Fish and Wildlife Service as threatened in 1985. In 2006, the Native
Fish Investigations Project
initiated a study to 1) determine population abundance and current
distribution of Warner suckers in the Warner basin, 2) describe the
population age structure, 3) search for evidence of sucker recruitment
in the lakes, 4) PIT and radio tag adult suckers to assess movements and
growth rates, and 5) determine the size (age) and timing of downstream
Warner Valley is
an endorheic basin which extends approximately 80 km from north to
south. The valley is bounded by fault block escarpments which rise 700
m above the valley floor (valley floor elevation is 1,370 m. The
pluvial Lake Warner, which formed during periods of abundant
precipitation in the Pleistocene era, had a maximum depth of 100 m and
an area of 1,250 sq. km. Currently several lakes are present in the
valley but only Hart, Crump, and Pelican are relatively permanent. When
adequate water is available, Warner suckers may inhabit all of the
lakes, sloughs, and potholes of the Warner Valley in southeastern
Oregon. Stream resident populations have been found in the three major
valley streams: Honey, Deep, and Twentymile Creeks.
The Warner sucker
has two overlapping life histories that have evolved in response to
environmental influences, the stream and lake residents. The lake
habitats are productive, but subject to periodic desiccation. Lake
suckers are larger than their stream counterparts. Stream suckers can
repopulate lake habitats after severe drought (for example, after
droughts in 1992 and the mid-1930’s). Stream habitats are influenced by
water withdrawals and grazing. Migration of adult lake-morph suckers to
spawning tributaries is impaired by irrigation dams and downstream
migration of stream-morph suckers is limited by unscreened diversions.
Numerous passage improvements
are being implemented and/or are in the planning
Warner suckers in
the lakes are considered potadromous, because they primarily spawn in
the streams and rear in the lakes. However, when streams are
inaccessible due to low stream flows or impassable barriers, lake
suckers have been observed spawning on limited lake shore gravel beds.
Spawning occurs in the spring (April through early-June) and is
associated with warming stream temperatures and relatively high spring
runoff. Adult suckers mature at 3-4 years and have been aged up to 17
Nonnative piscivorous fishes were stocked into the lakes in the 1970’s. Ratios of
crappies and brown bullheads have increased since the early 1990’s and
dominate the catch. In 2001, 87% of the fish captured in Hart Lake and
92% of the fish captured in Crump Lake were nonnative. These nonnative
fishes are believed to limit the recruitment of suckers in the lakes.
In recent investigations, the size (age) distribution of lake suckers
has been skewed toward larger, older adults.
Results from recent
investigations (2006-2010) include:
sucker abundance in Hart and Crump Lakes in 2006, 2008, and 2010.
Tracked movements of radio-tagged and PIT (passive integrated
transponder) tagged lake suckers in 2006, 2008, and 2009.
Obtained abundance estimates for stream suckers in Deep, Honey and
Twentymile Creek drainages in 2007.
Obtained a mark-and-recapture abundance estimate for suckers in the
Twentymile Creek subbasin in 2009.
Assessed spring movement patterns (spawning migrations) in
Twentymile Creek drainage and movements to the lakes in 2010.
We tracked PIT tagged suckers (~500 extant) using three PIT-tag
antennas, recaptured PIT-tagged suckers via electrofishing, and
tracked radio tagged fish (30 radio-tagged fish) on foot and
Identified spawning locations and timing of larval emergence and
movements in Twentymile Creek subbasin in 2010.
Initiated a sucker ageing study in 2010 and collected tissue samples
for future genetic analyses.
Annual Reports and Publications:
Scheerer, P. D., S. Clements, and J. T. Peterson. 2012.
2012 Warner Valley fish investigations- Warner suckers.
USFWS contracts F11AC00095 and F12AC01064, BLM contracts L10AC20356 and L12AC20619, and Ruby Pipeline funds.
Annual Progress Report, Corvallis.
Scheerer, P., S.E. Jacobs,
M. Terwilliger, S.A. Miller, S.L. Gunckel, S. Richardson,
and M. Heck.
and life history investigations of Warner suckers, 2006-2010.
Oregon Department of Fish and Wildlife, Information Report 2011-02, Corvallis.
Richardson, S. E., P. D. Scheerer, S. A. Miller, S. E. Jacobs, G. Swearingen, B. Berger, J. Deibner-Hanson, J. Winkowski, M. Terwilliger, and P. Hayden. 2009.
Warner Valley Fish Investigations- Warner
Suckers. Oregon Department of Fish and Wildlife, Contracts 13420-08-J814 (USFWS),
LO9PX00618 (BLM) and W66QKZ-90227-848 (COE), Annual Progress Report, Salem.
Scheerer, P. D., S. E. Jacobs, K. Bratcher, G. Swearingen, and S. Kramer. 2008.
Warner Valley Fish Investigations- Warner
Suckers. Oregon Department of Fish and Wildlife, Contracts HLP083003 (BLM),
E-2-50 and 134207M085 (USFWS), W66QKZ-8094-612 (ACOE), and T-17-1 (Conservation
Strategy), Annual Progress Report, Salem.
Scheerer, P. D., M. P. Heck, S. L. Gunckel, and S. E. Jacobs. 2008.
Warner sucker stream
investigations- Warner suckers. Oregon Department of Fish and
Wildlife, Contracts HLP073006 (BLM) and 134206M086 (USFWS), Annual
Progress Report, Salem.
Scheerer, P. D., S. E. Jacobs, and A. V. Munhall. 2006.
2006 Warner Valley fish investigations- Warner suckers.
Oregon Department of Fish and Wildlife, Fish Research Project HLP0630009 and 134206M093, Annual Progress