Projects FR-115, 123a, 123b, 123d, 128

Bureau of Reclamation Agreement Numbers and Grant Periods:

  • USFWS 123a: R20PG00024
  • UDWR-M 123a: R19AP00059
  • UDWR-V 123b: R14AP00059
  • CSU FR-115: R19AP00058
  • Colorado Pikeminnow: R14AP00001

Principal Investigators

Abstract

This annual report provides a comprehensive summary of all Smallmouth Bass removal conducted in the Green River sub-basin in the year 2023. It provides a population estimate for a limited segment of the Green River and comments on ages and size classes within that population. It frames the effectiveness of all electrofishing efforts within the context of varying environmental conditions through space and time and explores the possibility of seasonal movement patterns. Management recommendations are provided at the end of each section.

Introduction

Smallmouth Bass (Micropterus dolomieu) became established throughout the upper Colorado River basin in the early 2000s. Reservoir escapement and several years of favorable environmental conditions facilitated the establishment of self-sustaining populations which proliferated rapidly and expanded throughout the system (Anderson 2002, 2005; Bestgen et al. 2006, Hawkins et al. 2009, Breton et al. 2013, Breton et al. 2014).

The upper Colorado River Endangered Fish Recovery Program identified Smallmouth Bass as a threat to native fish assemblages and initiated efforts to control populations in each sub-basin. Mechanical removal efforts in the Green River sub basin began in 2003. This year marks two decades of dedicated bass removal.

This annual report provides a comprehensive summary of all Smallmouth Bass removal conducted in the Green River sub-basin in the year 2023 and frames the effectiveness of electrofishing efforts in the context of varying environmental conditions. It offers a current quantitative snapshot of the Smallmouth Bass population size and structure in the Green River sub-basin and compares this to historical trends. Management recommendations are provided at the end of each section.

This document is divided into the following five sections:

  • Section 1: Smallmouth Bass Removal Summary
  • Section 2: Abundance Estimate for Dinosaur National Monument
  • Section 3: The Context of Flow and Temperature
  • Section 4: Seasonal Movement Patterns
  • Section 5: Size Classes and Age Structure

Tables and figures are embedded within the text for each section to improve readability. Citations for all literature references appear at the end of the document.

Section 1: Smallmouth Bass Removal Summary

There are currently five funded electrofishing projects in the Green River sub basin (Figure 1). Project FR-115 is administered by Colorado State University’s Larval Fish Lab (CSU-LFL) and covers the Lodore and Whirlpool Canyon reaches. Project 123a is overseen by the U.S. Fish and Wildlife Service Vernal office (FWS-V) and Utah Division of Wildlife Resources – Moab (UDWR-M) and covers the Whirlpool, Island-Rainbow, Split Mountain, Desolation Canyon, and Gray Canyon reaches. Project 123b is managed by the Utah Division of Wildlife Resources Vernal office (UDWR-V) and covers the Jensen, Upper Middle Green, and Ouray, and Lower Middle Green reaches. Project 123d is overseen by UDWR-M and covers the Tusher Diversion reach. Project 128 is an interagency collaborative project that covers the Jensen, Upper Middle Green, Ouray, and Lower Middle Green reaches (UDWR-V), the Desolation and Gray Canyon reaches (FWS-V), and Labyrinth Canyon, Tower Park, and Stillwater Canyon reaches (UDWR-M).