7143

• UCREFRP Catalog Number: 7143
• Author: Inskip, P. D.
• Title: Habitat Suitability Index Models
• USFW Year: 1982.
• USFW - Doc Type: Northern Pike.
• Copyright Material: NO

should help with the identification of such lakes. Material presented in the
Habitat Use Information section of this document should allow the construction
of a SI graph for winter dissolved oxygen concentration, if such a variable is
appropriate for a particular model application.
The model applies to permanent rivers and streams with base flows > 50%
of the average annual daily flow and assumes an average depth > 0.5 m in pools
and backwaters. Those parts of intermittent tributaries that provide spawning
habitat for northern pike residing in a permanent river (or lake) should be
included in the determination of V1i V2, and U5.
It is common for northern pike to spend most of the year in a lake or
reservoir, but migrate upstream to spawn. In such cases, only the lacustrine
model need be applied. The utilization of upstream spawning sites is accounted
for in U1, which includes all accessible potential spawning areas. If,
however, both lake and stream habitat are to be evaluated as summer habitat,
the riverine model should be used for the stream and the lacustrine model for
the lake. The fact that northern pike may utilize spawning grounds at consid-
erable distance from areas inhabited during the rest of the year can make it
difficult to establish study area boundaries for rivers, large lakes, or
chains of lakes.
Water quality. The model is not applicable to waters overburdened with
sewage, those known to contain toxic substances or extreme concentrations of
particular solutes, or where heated discharge significantly alters the normal
thermal regime.
Minimum habitat area: The minimum area required for a self-sustaining
population of northern pike is not known. They occur in Ontario lakes as
small as 0.4 to 1.4 ha (Johnson et al. 1977).
Other. The model assumes the presence of at least one species of fish
that feeds primarily on macrophytes, plankton, macroinvertebrates, and/or
detritus. It is not necessary to specify abundance of potential prey species
because it is assumed that prey abundance is correlated with general system
productivity, as indicated by other model variables.
Verification level. The model represents the author's interpretation of
how specific environmental factors combine to determine overall habitat suit-
ability. The model has not been field tested.
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