9562

• UCREFRP Catalog Number: 9562
• Author: Hawkins, J., C. Walford and T. Sorensen.
• Title: Northern Pike Management Studies in the Yampa River, Colorado, 1999-2002.
• USFW Year: 2005.
• USFW - Doc Type: 98a,
• Copyright Material: NO

EXECUTIVE SUMMARY
Northern pike Esox lucius is a nonnative species that invaded the Yampa River,
located in northwestern Colorado, in the late 1970s and they now occupy the
mainstream river and several connected reservoirs. Northern pike are considered a
predatory threat to Colorado pikeminnow Ptychocheilus lucius, a federally endangered
species with critical habitat in the lower half of the Yampa River. We evaluated
mechanical removal of northern pike primarily from a 75-mile portion of the Yampa
River within critical habitat with the following objectives: 1) Remove juvenile and adult
northern pike from critical habitat reaches in the Yampa River, 2) Relocate northern
pike from the Yampa River to isolated ponds or reservoirs in or near the Yampa Valley
that conform to Nonnative Fish Stocking Procedures and are accessible to anglers, and
3) Determine effectiveness of removal in reducing the number of northern pike of all
sizes or reducing the number of large northern pike. All objectives were met.

A presumed northern pike spawning area upstream of critical habitat near
Hayden, Colorado and a major portion of critical habitat for Colorado pikeminnow were
sampled with boat electrofishing, fyke nets, and seines between 1999 and 2002.
During four years, 1042 northern pike were removed and translocated to Yampa State
Wildlife Area ponds or Rio Blanco Reservoir. Lengths of northern pike ranged from 28
to 1015 mm. Collection of young-of-year northern pike confirmed spawning and
nursery areas in the Hayden Reach in 1999. Downstream movement of juvenile and
small adult northern pike into critical habitat was supported by the distribution and
abundance of small adults that were captured predominantly in the most upstream
v