Species Fact Sheet Oregon chub Oregonichthys crameri
STATUS: THREATENED CRITICAL HABITAT: DESIGNATED
Oregon chub potentially occurs in these Oregon counties: Benton, Lane, Linn, Marion, Polk (Map may reflect historical as well as recent sightings)
The Oregon chub was listed as endangered in 1993. A
recovery plan was published in 1998. Critical habitat was designated on March 10, 2010. The species' status has recently improved, and on April 23, 2010, the USFWS changed the Endangered Species Act classification of the Oregon chub from endangered to threatened.
Historical Status and
Oregon chub are endemic to the Willamette River Valley of western
Oregon. Although information is scarce, the Oregon chub probably
occurred throughout the lower elevations of the Willamette River
valley. Historical records indicate that Oregon chub were found
as far downstream as Oregon City and as far upstream as Oakridge.
Historical records also report Oregon chub were collected from
the Clackamas River, Molalla River, South Santiam river, North
Santiam River, Luckiamute River, Long Tom River, McKenzie River,
Mary's River, Coast Fork Willamette River, Middle Fork Willamette
River, and the Willamette River from Oregon city to Eugene.
When the species was listed in 1993, there were eight known populations. By 2007, there were 38 known populations and this met the recovery criteria for downlisting (changing the classification from endangered to threatened). The USFWS downlisted Oregon chub to threatened status in 2010. Currently, there are 50 known populations; 19 of these populations have stable or increasing seven-year abundance trends. The improved status is attributed to successful introduction of Oregon chub into new locations within their historical range and the discovery of new, previously undocumented populations. The populations are found in the Santiam River, Middle Fork Willamette River, Coast Fork Willamette River, McKenzie River, and several tributaries to the Willamette River downstream of the Coast Fork/Middle Fork confluence.
Description and Life
The Oregon chub is a small minnow with an olive-colored back
grading to silver on the sides and white on the belly. Adults
are typically less than nine centimeters (3.5 inches) in
length. Scales are relatively large with fewer than 40 occurring
along the lateral line; scales near the back are outlined with
dark pigment. Adults feed in the water column on the tiny larvae
of aquatic invertebrates, such as mosquitos and other insects.
Spawning occurs from the end of April through early August when
water temperatures are between 16 degrees and 28 degrees C
(60 degrees and 82 degrees F). Only males larger than
25 millimeters (1 inch) spawn, and males more than 35 millimeters
(1.4 inches) defend territories in or near vegetation. Females
can lay several hundred eggs.
Oregon chub are found in slack water off-channel habitats such
as beaver ponds, oxbows, side channels, backwater sloughs, low
gradient tributaries, and flooded marshes. These habitats usually
have little or no water flow, silty and organic substrate, and
aquatic vegetation as cover for hiding and spawning. The average
depth of Oregon chub habitats is typically less than two meters
(six feet) and the summer water temperature typically exceeds
16 degrees C (61 degrees F). Adult Oregon chub seek dense vegetation
for cover and frequently travel in the mid-water column in beaver
channels or along the margins of aquatic plant beds. Larval chub
congregate in near shore areas in the upper layers of the water
column in shallow areas. Juvenile Oregon chub venture farther
from shore into deeper areas of the water column. In the winter
months, Oregon chub can be found buried in the detritus or concealed
in aquatic vegetation. Fish of similar size classes school and
feed together. In the early spring, Oregon chub are most active
in the warmer, shallow areas of the ponds.
Reasons for Decline
Historically, the main stem of the Willamette River was a braided channel with many side channels, meanders, oxbows, and overflow ponds that provided habitat for the chub. Periodic flooding of the river created new habitat and transported the chub into new areas to create new populations. The construction of flood control projects and dams, however, changed the Willamette River significantly, and prevented the formation of chub habitat and the natural dispersal of the species. Other factors responsible for the decline of the chub include: habitat alteration; the proliferation of non-native fish and amphibians; accidental chemical spills; runoff from herbicide or pesticide application on farms and timberlands or along roadways, railways, and power line rights-of-way; the application of rotenone to manage sport fisheries; desiccation of habitats; unauthorized water withdrawals; diversions, or fill and removal activities; sedimentation resulting from timber harvesting in the watershed; and possibly the demographic risks that result from a fragmented distribution of small, isolated populations. The introduction of non-native fish and amphibians continues to threaten existing populations of Oregon chub; many non-native species (such as bass, mosquitofish, and bullfrogs) occur in the same type of habitat as Oregon chub and eat small fish, including the chub.
in 1998, the U.S. Fish and Wildlife Service published a recovery
plan for the Oregon chub. The goal of this plan is to reverse
the decline of the Oregon chub by protecting existing wild populations,
re-introducing chub into suitable habitats throughout its historic
range, and increasing public awareness and involvement. The
U.S. Forest Service, Army Corps of Engineers, and the Oregon
Department of Fish and Wildlife have active programs to protect
the Oregon chub. Careful and coordinated planning, management,
and protection of Oregon chub habitat is necessary for the survival
of this little minnow.
U.S. Fish and Wildlife Service. 2010. Reclassification of the Oregon Chub From Endangered to Threatened. FR (75):21179-21189
U.S. Fish and Wildlife Service. 2010. Designation of Critical Habitat for the Oregon Chub. Federal Register.