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

The model is designed to assign the highest HSI's to systems capable of
producing the most northern pike biomass per unit time on a sustained basis,
regardless of how that biomass is apportioned among individual fish. Few long
term data are available on production, yield, standing crop, or other measures
of population performance for northern pike under different environmental
conditions. Therefore, behavioral observations and measures of individual
performance, such as growth and survival, were also used to develop suitability
index curves for model variables. The rationale and assumptions used to
develop the curves are presented in a following section.
Modifications to the model, such as including different or additional
variables, may be necessary in some situations. The model is structurally
.simple, and madifications are easily made.
Model Applicability
Geographic area. The model is applicable to lakes, reservoirs, rivers,
and streams throughout North America.
Season. The model is structured to account for seasonal changes in
weather and habitat requirements of northern pike and, thus, to indicate the
ability of a'-given habitat to sustain a population on a year-round basis.
Overwintering requirements may not be adequately addressed for northern pike
in shallow lakes~or low discharge rivers that experience extended ice cover
(see below).
Cover types. The model is applicable to permanent lakes, ponds, and
reservoirs with a mean depth _> 1 m during midsummer. It is of doubtful reli-
ability .for shallow lakes (even those with mean depths > 1 m) that are covered
with ice for long periods. The suitability index graph for V3 (curve A) is
the only part of the model-that addresses the possibility of winterkill of
northern pike due to low dissolved oxygen concentrations. It is recognized
that any single variable is an inadequate indicator of the occurrence and
severity of this phenomenon. However, an accurate, general model for predict-
ing winter dissolved oxygen concentrations, based on easily measured or
predicted habitat characteristics, does not exist. [The empirical techniques
developed by Barica and Mathias (1979) for predicting winterkill in shallow
prairie lakes may be useful in some cases.] Because some of the factors that
affect the likelihood of winterkill are highly variable from year to year,
dissolved oxygen measurements for a single winter do not -adequately indicate
the likelihood of occurrence of winterkill in a given lake over a series of
years. The fact that northern pike can find and use pockets or layers of
water with relatively high oxygen concentrations (Magnuson and Karlen 1970;
Scidmore 1970} further complicates the modeling problem. Habitats that
experience occasional, partial winterkill of northern pike may nonetheless be
highly productive of northern pike. Rather than include additional variables
with no guarantee of improved model accuracy, it was decided to keep the model
simple and emphasize its questionable applicability to potential winterkill
lakes. Information presented by Greenbank (1945) and Schneberger (1970)
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