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

that could flush northern pike fry into the main channel. It has been well documented
that age-O pike are reliant upon vegetated nursery habitat for survival. Holland and
Huston (1984) found that age-O pike were 10 times more abundant in backwater areas
with vegetation compared to areas lacking vegetation. During a normal water year the
main channel of the Yampa River is devoid of calm, well vegetated areas, except for river
backwaters. We would expect that successful recruitment of age-O pike could only take
place if they are able to remain in these backwaters, or able to return to these areas after
being forced into the main channel. Large numbers of age-O pike were never found in the
main channel or in the backwaters, suggesting that recruitment from these Yampa River
habitats is limited.

Well-managed northern pike spawning marshes are capable of producing in
excess of 200 age-O northern pike per year per 557 m2 (Royer 1971). No riverine
spawning sites we investigated came close to producing this many pike. Age-O pike were
typically mobile and visible during electrofishing collections. The majority of
backwaters sampled had few age-O pike and few were observed during sampling.
Therefore, we do not believe a large number of age-O pike were present. The specific
sites we intensively sampled for age-O pike appeared to us to be the best sites available in
the entire study area. They were among the larger sites and were generally isolated from
the negative impacts of spring runoff flows. The combination of small spawning areas,
large water level fluctuations, and disruptive flows lead us to believe that the number of
successful backwater spawning locations on the Yampa River is very limited.

Nesler (1995) reported that over a four-year period of sampling with seines and
electrofishing between river mile 45.4 and 152.5 only 3 age-O northern pike were
collected, all from areas upstream of river mile 139 (Craig). Our sampling for age-O pike
in backwaters typically resulted in zero to 5 age-O pike in an entire sampling area, with
only a few occasions resulting in 10 to 25 age-O pike in an entire backwater. Overall, the
greatest numbers of age-O pike were found at the gravel pit pond site. Based on the
apparent stability of the gravel pit and other off channel ponds and their relative impunity
to variations in river flows, it is not surprising that the gravel pit pond would produce the
greatest number of age-O pike. The pond site we examined was less prone to water level
fluctuations than those sites more directly influenced by the Yampa River and was more
similar to stable lentic environments often associated with good northern pike habitat.

While our sampling of pond habitat only included one site, we believe that the
majority of successful northern pike recruitment takes place in off channel ponds.
Analysis of aerial photographs showed that there are as many as 72 such ponds totaling
about 158 ha along the Yampa River that are always open to the river or could be
connected during spring runoff. Most of these ponds are clustered near . Steamboat
Springs and Craig and typically are remnants of gravel mining operations. Ponds that are
connected to the river are likely sources of northern pike recruitment. The more isolated
ponds could also account for a significant infusion of age-O northern pike to the river if
they are deep enough to support over winter survival of adults. In such cases, young
northern pike could move into the river every few years when the spring flows are large
enough to connect the pond with the river.. We also found northern pike escaping from

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