8178

• UCREFRP Catalog Number: 8178
• Author: Anderson, R. and G. Stewart.
• Title: Riverine Fish Flow Investigations.
• USFW Year: 1999.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

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State: Colorado

Project No. 7400 ENDG 0700

Name: Aquatic Nongame Research

Study No. SE-3-22

Title: Riverine Fish Flow Investigations

Period Covered: July 1. 1997 - June 30.2002

Study Objective:

To determine relationships between flow and habitat availability
for warm-water riverine fish communities of Colorado.

INTRODUCTION

Habitat loss is one of the single greatest causes of decline in populations of
native fishes in North America (Williams et al. 1989). While there clearly must be some
minimum flow needed to maintain a healthy, functioning river community, methods to
establish minimum flows on warm water river sections have proved controversial. Most
in stream flow studies implemented in Colorado have focused on protecting minimum
stream flow for cold water (headwater) habitats using either the R2Cross method
(Nehring 1979) or Instream Flow Incremental Methodology (IFIM) (Bovee 1982),
which determines habitat availability based on a single target species. IFIM estimates
the amount of usable habitat for fish as a function of discharge by combining habitat
suitability curves with the hydraulic model. The habitat component of the model has
received much criticism because of assumptions implicit with using suitability curves
and assumptions of positive relationships between habitat availability and fish
abundance. Validation of these assumptions have been obstacles for successfully using
IFIM to model minimum flow impacts on large warm water rivers of the west slope
(Rose and Hahn 1989).

Warm water fish assemblages appear to require a more intensive approach to
in stream flow modeling compared to cold water fish communities. Warm water river
reaches tend to be lower gradient and have higher channel complexity and.sediment
loads. Warm water fish populations tend to have higher species diversity. Also habitat
suitability curves derived from microhabitat observations do not adequately describe
habitat use for many warm water species. A broad community-level perspective, as
opposed to an indicator species approach, may be required to protect all habitats of a
functioning warm water stream ecosystem.

Instream flow techniques require integration of two processes that combine
detailed knowledge of habitat requirements (by species and life stage), and the
availability of necessary habitats. Both the collection and analysis of these data bases
have been very labor intensive. Recent advances in surveying techniques (e.g. G.P.S.)
and computer capabilities (G.I.S.) allow for collection and processing of much larger
databases. Also, two-dimensional (2-D) flow models may have potential for application
in in stream flow studies (Leclerc et al., 1995; Bovee, 1996). In theory, 2-D models offer
a significant improvement over one-dimensional (I-D) modeling by increasing spatial

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