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

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Steamboat Springs and Craig vary due to additional inputs between gage stations, an
estimated flow at each backwater site was calculated. The difference in flow between the
most upstream gage station and the most downstream gage station in the study area was
divided by the total distance to get a flow gain/loss per mile. The distance from the most
upstream gage station to each site was calculated to determine the appropriate flow per
mile to add or subtract. Using this information a depth gage reading vs. flow relationship
was developed for each backwater. A polynomial regression line was fit to the data and
the equation of this line was used to calculate the depth of the backwater for any flow of
interest.

Detailed habitat surveys were performed at the same nine backwaters where depth
gages were installed. A surveyor level (CSTlBerger Laser One, Watseka, IL) was used to
determine the bottom contour of each backwater by measuring depths along transects
perpendicular to the long axis of the backwater. Transects were spaced between 9.1 and
27.4 m depending on bank obstructions and the size of the backwater. Backwaters
smaller than 101 m long had at least 6 transects and backwaters longer than 101 m had
between 10 and 17 transects. Depth measurements were recorded every 0.9 to 2.7 m
along the transect. Arcview spatial analyst (ESRI, Redlands, CA) was used to construct a
contour map from the survey data. The regression of depth gage reading vs. flow and the
contour map for each site was used to determine wetted area in each backwater during the
spawning and nursery periods. During 2002 and 2003 the average flow from April 1 - 15
was used to determine the wetted area in each site for the spawning period. The peak
flow recorded for 2002 and 2003 was used to determine the maximum wetted area in the
backwater and possible connectivity to the main river channel.

During 2002, the four sites where spawning adults were collected in the trapnets
and seven other backwaters were sampled for age-O northern pike with a Smith-Root
backpack electrofishing unit. During 2003, another site at river mile 169.1 was sampled
in addition to the 11 from the previous year. An attempt was made to sample each site 3
times each year. Sampling took place during three periods; the end of June, the
beginning of July, and the end of July. Dewatering associated with low flows and
decreased flows over the summer precluded sampling at several sites in both 2002 and
2003. These sampling occasions are reported as catch per 10 minutes of electrofishing
effort (CPUE) because each site varied by size.

Evaluation of Barriers
Barrier materials tested included the seine/trapnet used to collect spawning adult
pike, a patchwork of materials including hardware cloth, poultry wire with 2.5 cm mesh,
Kevlar coated net with 2.5 cm mesh, Kevlar coated net with 6.4 mm mesh, and
polyvinylchloride (PVC) coated poultry wire with 2.5 cm mesh.

The barrier design used to determine the effectiveness of barriers consisted
entirely of PVC coated poultry wire. This barrier extended from the top of one bank to
the top of the opposite bank to deny fish access as the water rose during the spawning
period. T -bar posts were spaced about every 1.5 m to support the fencing. Nylon zip ties
were used to attach fencing panels to each other and to the posts. On dry ground below

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