9578

• UCREFRP Catalog Number: 9578
• Author: Hamilton, S. J. and e. al.
• Title: The Evaluation of Contaminant Impacts on Razorback Sucker Held in Flooded Bottomland Sites Near Grand Junction, Colorado - 1997.
• USFW Year: 2001.
• USFW - Doc Type: CAP6-WW,
• Copyright Material: NO

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lower Colorado River basin and reported selenium contamination throughout the upper and
lower Colorado River basin. He concluded that selenium concentrations Were sufficiently
elevated to be causing reproductive problems in endangered fish such as the razorback sucker.
In a follow-up paper, he reviewed historical data on selenium concentrations in the upper and
lower basins, along with historical records and reviews of the occurrence of native, later
endangered fish, and presented a hypothesis that suggested selenium contamination from
irrigated agriculture in the 1890-1910 period caused the decline of native fish in the upper basin
in the 1910-1920 period and in the lower basin in the 1925-1935.period (Hamilton 1999).
Although many of the studies reviewed in Hamilton (1998, 1999) documented elevated selenium
concentrations in various aquatic components, none of the studies assessed biological effects in
endangered fish from exposure to selenium or other inorganic elements.
In an effort to stabilize and enhance populations of razorback sucker and other
endangered fishes in the upper Colorado River, the Floodplain Habitat Restoration Program
within the Recovery Program undertook to restore floodplain habitats for use by razorback
sucker larvae and adults. The proposed strategy for achieving these goals was to reconnect
selected floodplain habitats to the main river channel in a manner that simulated historic
hydrological conditions. An important component of this Restoration Program was to select sites
that after restoration, would not pose contaminant problems to the fish, especially from selenium.
This study was conducted to derive the necessary toxicological information for assessing the
suitability of selected flooded bottomlands as habitat for razorback sucker.

Razorback sucker

The life history and status of the razorback sucker has been reviewed by Bestgen (1990).
Briefly, the razorback sucker was considered common in the upper and lower Colorado River
basins in historical times, but since the 1940's has become rare except for populations in the
Green River and Lakes Mead and Mohave. Razorback suckers are generally thought to inhabit
moderate to large streams and rivers and use a variety of habitats including low-velocity areas
(backwaters, sloughs, oxbow lakes), near-shore runs, and shallow channels adjacent to, or over,
mid-stream sandbars. The diet of razorback sucker varies depending on life stage, habitat, and
food availability, and the diet of adults in rivers may be different than adults in reservoirs. '
Springtime congregations of razorback sucker have been found in off-channel impoundments
and tributaries. Spawning behavior of razorback sucker is apparently influence by water
temperature and flow (Tyus and Karp 1990), but Modde and Wick (1997) suggested that
increases in discharge probably have a greater influence on initiating fish movement in late
spring to spawning sites such as Razorback Bar in the Green River.
The remaining population of razorback sucker in the middle Green River basin in Utah
has been estimated, using similar datasets, at about 1,000 individuals in 1988 (Lanigan and Tyus
1989) and at 300 to 600 in 1992 (Modde et al. 1996). Razorback sucker are rare in the upper
Colorado River basin, where only 10 fish were found in the river between 1989 and 1996 (C.
McAda, USFWS, personal communication).
The present study was conducted at three sites near Grand Junction, CO, in the general
area where razorback sucker had historically been observed, i.e., the gravel pit at what is now
Walter Walker State Wildlife Area, or is currently held in hatchery ponds for propagation
purposes, i.e., Horsethief Canyon State Wildlife Area. Although wild fish are free to move about