7618

• UCREFRP Catalog Number: 7618
• Author: Rose, K. L. and D. R. Hann.
• Title: Summary of Historic Habitat Modeling on the Yampa River Using the Physical Habitat Simulation System
• USFW Year: 1989.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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INTRODUCTION

Biological studies have demonstrated the importance of the Yampa River as
spawning habitat for Colorado squawfish (Ptychocheilus lucius) (Archer and
Tyus 1984; Haynes et al. 1984), and as habitat for the adult life stages of
both Colorado squawfish (Wick et al. 1983; Haynes et al. 1985), and humpback
chub (Gila ~) (Tyus and Karp 1989). It is evident from repeated captures
of ripe fish that the majority of Colorado squawfish and humpback chub
spawning activity (i.e., the actual deposition and fertilization of eggs) in
the Yampa occurs in a unique reach between river mile (RM) 12 and 20. Adult
Colorado squawfish (450+ mm in total length) have been captured throughout the
Yampa River from the mouth to near the town of Hayden, Colorado (P. Martinez,
Colorado Division of Wildlife, personal communication). Concentration areas
include from the confluence with the Little Snake River upstream to Juniper
Canyon, RM 51 to 89, and from Juniper Canyon upstream to Round Bottom, RM 91
to 124. Adult humpback chub (200+ mm in total length) have been captured from
Yampa Canyon upstream to Cross Mountain, RM 18 to 56, with concentrations, and
spawning activity presumably occurring within Yampa Canyon from RM 18 to 37
(Tyus and Karp 1989).

Historic flows of the Yampa River, largest tributary of the Green River, have
not been significantly altered by dams (Miller et al. 1982). However, several
water development projects are planned which may significantly alter existing
flows, and consequently, the riverine habitats used by endangered fishes. A
primary goal towards the recovery of these fishes is the acquisition and
management of instream flows. This can best be accomplished in the Yampa
River by acquiring and appropriating sufficient water rights to maintain
current populations of fishes and protect their habitats.

Through application of the Physical Habitat Simulation System (PHABSIM), as
described by Milhous et al. 1984, the computer simulation of physical
microhabitat for Colorado squawfish and humpback chub as a function of stream
flow has been attempted. As early as 1978 researchers began to investigate
the feasibility of applying instream flow methodologies to endangered fishes
on the Yampa River. Prewitt et al. (1982) reported results from five instream
flow study sites on the Yampa River. Study sites were located at Box Elder
(RM 2), Cleopatra's Couch (RM 16.5), Lilly Park (RM 50), Cross Mountain (RM
53) and Maybell (RM 72). Habitat suitability index (SI) curves for young-of-
the-year, adult and spawning Colorado squawfish were developed from depth,
velocity and substrate data collected throughout the Green and Colorado Rivers
during 1979 through 1981. PHABSIM was used in an attempt to simulate physical
habitat availability as a function of discharge. Prewitt's results were
inconclusive and were not supported by species experts because flows suggested
by model outputs as providing optimal habitat conditions had never been
observed in the Yampa River.

In 1983 the Fish and Wildlife Service established two new PHABSIM study sites
on the Yampa River and developed new SI curves for spawning and adult Colorado
squawfish from data collected on the Yampa River only. Rose (1984) reported
the results of these studies; however, they did not support biological
observations and were again rejected by species experts.