7193 - Laserfiche WebLink

Home Browse Search

1986-87 Job Progress Report State: Colorado Project No.: 02-01-035 Name: Aquatic Nongame Research Study No.: SE-3-ll Title: Endangered Fishes Investigations Period Covered: July 1, 1986 - June 30, 1987 Study objective: To assist in the recovery of the endangered fish species in the Upper Colorado River Basin. INTRODUCTION These investigations were split into two distinct areas of concern. The first involved participation by the State of Colorado in the endangered fishes standardized monitoring program, directed by the U.S. Fish and Wildlife Service, Region 6. This program is directed at annually evaluating the status and trends of populations of the endangered fishes at one or more life stages. The second area concerned research into aspects of the early life history of the Colorado squawfish (Ptychocheilus lucius) in the Yampa - Green river subbasin. The Recovery Plan for this species calls for identification of habitat requirements and limiting factors within its life history in order to enhance recovery measures (U.S. Fish and Wildlife Service 1984). Studies by the Colorado Division of Wildlife were directed at determining specific characteristics of the larval transport mechanism displayed by Colorado squawfish larvae as they drift from the major spawning area, Yampa Canyon, in the Yampa River in Colorado to the major nursery backwaters in the Green River around Jensen, Utah. Important factors included their rate of downstream drift, relative changes in the abundance of drifting larvae, and the downstream range exhibited by drifting larvae under variable flow regimes. During this vulnerable period, sources of mortality to the larvae such as predation, thermal shock, food competition, and physical stranding were to be investigated. During the 1986-87 segment, activity in the standardized monitoring program included seining in the Colorado River from Loma to Stateline in September 1986 to determine catch-per-unit effort indices (c/f) for fall young-of-the-year (YOY) Colorado squawfish, and electrofishing five river reaches including parts of the Yampa, White and Colorado rivers in April 1987 to determine clf indices for adult Colorado squawfish. Research activity included preliminary investigations into the feasibility of marking larval Colorado squawfish prior to the drift stage, and an evaluation of drift-net sampling in the Yampa River as a representative technique for collecting larval squawfish. Results of these efforts are reported here in Job I-Standardized monitoring surveys, and Job 2-Larval drift studies.