9509

• UCREFRP Catalog Number: 9509
• Author: Hill, C. G.
• Title: Dynamics of Northern Pike Spawning and Nursery Habitat in the Yampa River, Colorado.
• USFW Year: 2004.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

the top of the bank the fencing was inserted into a trench and backfilled. In wetted areas,
the bottom 30.5 cm of the fence was folded to lie flat along the bottom and 32 kg
sandbags were placed on the folded fence material to hold it firmly to the substrate.
Fence panel length varied as necessary to accommodate the variations in bank and
channel shape. A variation to this design included placing rebar posts in front of the
sandbag and through the fen<~e underneath the sandbag to ensure that the sandbags could
not move out of place.
The barrier design using the PVC coated poultry wire was used to evaluate the
best time of the year to install barriers. Two barriers were installed during November
2002: one at river mile 197.8 and the other in the marshy area connected to the gravel pit
pond at river mile 197. A third barrier was installed at river mile 152.5 during March
2003 before ice came off the river and backwater. At this site a channel was cleared
across the backwater from which all ice was removed. Snow on the banks was removed
down to the ground. Installation of the barrier then followed the same procedure used for
installation of the other PVC coated poultry wire barriers.

To determine landowner acceptance of a pike barrier program, all landowners
along the Yampa River between Steamboat Springs and Craig were sent a questionnaire
by the Colorado Division of Wildlife and the Yampa River Basin Partnership (a Yampa
River advocacy group) asking whether they would allow barriers to be placed on their
property to block northern pike from spawning habitats. Property ownership information
available from the Routt and Moffat County Assessor's office was used to compile the
mailing list.

Results

Assessment of spawning and nursery habitat characteristics
The spring runoff in the Yampa River in 2002 was well below average, while in
2003 it was above average (Figure 2). Peak stream flow in 2003 at Steamboat Springs
was the 16th highest on record, while in 2002 the peak spring flow was only 10 cfs above
the record low of 1,080 cfs. Ice cover on the Yampa River broke up during February and
March. Increasing flows during April allowed access to backwaters that were dry, or
inundated additional vegetation in backwaters that held some water over the winter.
Early runoff in May provided access to additional backwaters. Peak runoff, depending
on the magnitude, had the potential to completely flood the river valley and provide fish
access to fields and flood plain ponds.

During 2002, we documented the presence of spawning northern pike in early
April soon after the ice on the river broke up and as water temperatures began to rise.
Peak use of the backwater spawning habitat by sexually mature northern pike occurred in
early April (Figure 3). Expression of gametes determined sexual maturity. Our
collections of pike at this time consisted of many more males than females. By mid May
very few sexually mature northern pike were collected entering or exiting the backwater
habitats. During 2002, temperature loggers were installed at the same time as the
trapnet/seine, and water temperatures were at or above 7.80 C in the river and in the

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