7733

• UCREFRP Catalog Number: 7733
• Author: McAda, C. W.
• Title: Evaluation of Aerial-Video Measurement of Backwaters as Part of the Interagency Standardized Monitoring Program for Age-0 Colorado Squawfish.
• USFW Year: 1993.
• USFW - Doc Type: \
• Copyright Material: NO

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INTRODUCTION
The Interagency Standardized Monitoring Program (ISMP) began in 1986 during the
coordination process that ultimately resulted in the Recovery Program for the Endangered
Fishes of the Upper Colorado River Basin. ISMP was developed jointly by representatives
from the States of Utah and Colorado, Fish and Wildlife Service (Service), Bureau of
Reclamation (Bureau), and Water Development interests that comprised the Biological
Subcommittee of the Upper Colorado River Basin Coordinating Committee. The program
involved annual sampling in areas already identified as important to one life stage of one of
the endangered fishes. The program targeted young-of-the-year (YOY) and adult Colorado
squawfish Ptychocheilus lucius, and adult humpback chub Gila cypha. It specified sampling
procedures that could be used to monitor trends in the population status of these fishes.
ISMP was modified in 1989--this document evaluates one of the changes in YOY Colorado
squawfish monitoring initiated that year.
The YOY Colorado Squawfish Monitoring Program was designed to systematically
sample reaches known as important habitat for small Colorado squawfish. Previous
researchers (Tyus et al. 1982; Valdez et al. 1982; Jones and Tyus 1985; Archer et al. 1985)
had identified two river reaches in each of the Green and Colorado rivers where most post-
larval Colorado squawfish were found. Although small Colorado squawfish were found in
other areas, these reaches contained most squawfish of this size. These important areas were
between river miles 0 to 120 and 200 to 319 in the Green River and between river miles 0 to
110 and 140 to 170 in the Colorado River. These investigators had also shown that the
majority of small Colorado squawfish were collected in backwaters or embayments--quiet
water areas along islands or the main shoreline, usually surrounded by land on three sides.
Fish utilized other quiet-water habitats, but were most consistently collected in backwaters or
embayments. Tyus and Haines (1991) captured only 16% of the young squawfish they
handled over a three year period from habitats other than backwaters (shorelines, side
channels, runs, and eddies). The higher catch rate in backwaters may be related, in part, to
higher sampling efficiency in this type of habitat than others, but nonetheless reflects a
preference for backwaters by postlarval Colorado squawfish.
The Service began a fall inventory of the relative abundance of post-larval Colorado
squawfish in the Green River in 1979 (Tyus et al. 1982) and in the Colorado River in 1982
(Archer et al. 1985). This inventory was intended to provide an annual index of the relative
reproductive success and survival of young Colorado squawfish. Investigators began at the
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