7419

• UCREFRP Catalog Number: 7419
• Author: Valdez, R. A., et al.
• Title: Summary Documentation and Preliminary SI Curves, SI Curve Development Project.
• USFW Year: 1987.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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INTRODUCTION

BACKGRCUrn

The Fish and Wildlife service (FWS) is using the Instream Flow Incranental
Methodology (IFIM) as a tool for evaluating the habitat requiranents of the
endangered Coloraio River fishes in the upper Colorado River Basin (UCRB).
IFIM is a nn:lular system designed to simulate habitat as a function of stream-
flew (Bovee 1982, Milhous et al. 1984). SUitability Index (SI) curves, which
are an integral conponent of IFIM, are graphs that represent the relative
preferences and tolerances for variables (depth, veloci t:y, substrate, cover,
and tenperat:ure) that are important to the well-being of a species. several
techniques are available for developing SI curves (Bovee 1986); the method
utilized is often dependent on the quantity and qua,li ty of data available.

Data have been collected over the last several years to detennine the
habitat needs of the Colorado squawfish, hun'pback chub, and razorback sucker in
the UCRB. Much of these data w:!re used by FWSto develop SI curves in 1984
(U.S. Fish and Wildlife service 1984). There was some concern, hcwever, that
data from other agencies and organizations \ere not included in the analysis
( only FWS data w:!re used), and that developnent of the curves was not well
documented. Also, there was not general agreement concerning data analysis and
curve developnent methods that w:!re utilized by FWS in the 1984 exercise.

The FWS had assanbled most of the kncMn habitat utilization data collected
l:7y state, federal, and private agencies/groups for the endang'ered fish of the
UCRB, and entered the data into a canplterized datal:ase. A need existed to
integrate missing data and analyze all data; develop SI curves for all vari-
ables, life stages, and species; identify data gaps and needs; and for species
eJCPSrts to evaluate the data and reach agreement on the best possible. curve
sets given the present kncwledge. A consensus by species elCpSrts was required
to detennine which data were suitable for analysis, hl:w curves were to be
developed, and when and where the UCRB curves are applicable.

PROJECT OBJECTIVES

The goal of this project is to generate the best possible SI (SUitability
Index) curves or criteria for depth, velocity, substrate, cover, and tanpera-
t:ure using the existing data and the professional judganent of species experts,
for all life stages of the Colorado squawfish, humptack chub, and razorback
sucker. The lxmytail chub was excluded from this analysis because of its
extreme rarity in the upper Basin and the absence of sufficient quantitative
data. To acconplish this goal, the follCMing objectives are to be met:

1 . Based on judgement of eJ.CP8rts, detennine which data wi thin the
canplterized data1:ase are suitable for quantitative analysis and use
in SI curve developnent, versus those which are only useful for
substantiating use of certain habitat variables and types.

1