9528 ‎(2)‎

• UCREFRP Catalog Number: 9528
• Author: Martinez, P. and N. P. Nibbelink.
• Title: Colorado Nonnative Fish Stocking Regulation Evaluation.
• USFW Year: 2004.
• USFW - Doc Type: Grand Junction, Laramie.
• Copyright Material: NO

1
1
INTRODUCTION
General
Nonnative fish species are suspected of having a significant negative impact on the
' current status and recovery potential of the Colorado River endangered fishes (common and
scientific names, including species codes for fishes mentioned in this report are found in
Appendix )7. Attempts to control and minimize these impacts have been reviewed by Hawkins
' and Nesler 1991, Lentsch et al. 1996, PDO 2002, Tyus and Saunders 1996 and 2000. Shallow,
shoreline habitats with little or no current (backwaters, embayments, side channels) are
considered to be vital nursery habitats for native fishes, particularly for the young of endangered
' Colorado pikeminnow (Byers et al. 1994, Osmundson 2000). Seasonally inundated bottomlands
and floodplain depressions are considered to be important nursery habitats for the young of
endangered razorback sucker (Burdick 2002, Osmundson 2000). Recent data show that
' backwaters within the Colorado and Gunnison rivers are dominated by nonnative fishes which
comprise 90-99% of the species composition (Anderson 1997, Bundy and Bestgen 2001, Burdick
1995, McAda et al. 1994 and 1996, Tramme112002). In addition, recent examinations of
floodplain habitats reconnected to the Colorado River have also shown a seasonal preponderance
of nonnative fishes (Burdick et al. 1997 and 2002).
' Control of nonnative fish in the Upper Colorado River Basin (UCRB) is defined as
"reducing the numbers of one or more nonnative species to levels. below which they are no
longer an impediment to the recovery of endangered fish species" (Tyus and Saunders 1996 and
2000). Control of nonnative fish within Colorado has been pursued through several approaches.
These include: (1) removal of bag and possession limits on nonnative, predatory gamefish
species within designated critical habitat (Martinez 1998 and 1999), (2) authorization of
' Recovery Program participants to remove nonnative fish incidental to approved project sampling
objectives through scientific collection permits (T. Nesler, CDOW, personal communication), (3)
removal of nonnative fish from backwater habitats in the Colorado River by seining and
electrofishing (Bundy and Bestgen 2001, Osmundson 2003, PDO 2002, Trammell et al. 2002)
(4) removal of nonnative fish captured in the Redlands passageway on the Gunnison River
(Burdick 2001), (5) removal of nonnative fish from backwater, slough and main channel habitats
' in the Yampa River during spring runoff (Hawkins and Nesler 2001, PDO 2002, Pfeifer and
McAda 2001), (6) removal of channel catfish in the lower Yampa River (Modde and Fuller), (7)
removal of nonnative fish from ponds in the Colorado and Gunnison river floodplains via
' chemical reclamation and water level management (Martinez 2001 a, PDO 2002), and (8)
regulation of the release ofnon-native fishes via stocking into public and private waters within
designated critical habitat and a buffer zone bounded by the 6500-feet elevation isopleth, and in
' other waters via lake licenses and stream stocking permits (Martinez 2001b and 2002, Nesler and
Martinez 2001, PDO 2002). This latter component is the primary focus of this investigation.
Background
The Procedures for Stocking Nonnative Fish Species in the Upper Colorado River Basin
(hereinafter Procedures) were adopted by the state wildlife agencies of Colorado, Utah and
Wyoming, and the U.S. Fish and Wildlife Service (CTSFWS), Region 6, on 5 September 1996