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

Methods

Assessment of spawning and nursery habitat characteristics
During 2002, four sites were sampled to determine when northern pike were using
the backwaters and when they spawn. A nylon seine with 38.1 mm mesh and leadcore
bottom line was stretched across the mouth of each backwater with two trapnets attached
to holes cut in the seine. Steel posts were installed on each bank and in the backwater to
secure the seine and trapnets. One trapnet collected fish moving into the backwater and
the other collected fish as they moved out of the backwater. Each northern pike caught
was tagged with an individually numbered t-post tag, weighed (lb, oz), measured (in),
checked for eggs or milt, and released in the backwater or in the main channel depending
on the direction it was moving. The seine/trapnets were installed on April 9-16, 2002 and
checked daily for five weeks.

Water temperatures were measured in the main river channel and in backwaters to
determine temperatures associated with pike spawning activity. Temperatures were
recorded with Onset Optic StowAway temperature loggers in the Yampa River at
Steamboat Springs (river mile 197), near Hayden (river mile 169.1), and near Craig (river
mile 137). Loggers were installed in the mouth of backwaters at river miles 174, 163.8,
and 163.3 and at the gravel pit pond at river mile 197 in early April 2002 and remained in
place throughout the study. Additional temperature loggers were installed at backwaters
at river miles 197.8 and 152.5 in April 2003.

Aerial photographs taken September 5, 1999 were analyzed to determine the
potential abundance of backwaters. The river was navigated by canoe from the west end
of Steamboat Springs to Craig to identify the location and distribution of backwater
spawning sites. A global positioning system was used to record the location of each
backwater. Habitat measurements at each site consisted of length and width
measurements, backwater orientation to the river, depth at mouth of the backwater, and
evidence that the backwater became part of the flowing channel during spring runoff.
Because spring runoff flows can seriously impact spawning habitat, we attempted to
categorize possible backwater spawning areas not only by size, but also by orientation to
the river and by visual signs that spawning habitat was exposed to flushing flows during
spring runoff. The bank separating the backwater from the river was assessed for the
presence of vegetation and bank composition to indicate whether the backwater became a
flowing side channel or was simply inundated during spring runoff. The presence of
vegetation and dirt banks indicate that the backwater probably was not often part of the
flowing channel during spring runoff, while a predominantly cobble bank that lacked
vegetation indicated that the backwater probably experienced flushing flows during
spring runoff. A combination of vegetation characteristics and bank composition,
intermediate between the two previous categories was used as an indication that the
backwater was exposed to main channel flows intermittently.

Depth gages were installed at nine backwater sites to record changes in water
level over the spawning and nursery period. Depth gage readings were recorded during
April, May, and June. Because river flows reported at USGS gage stations located at

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