Operational Plan for the Restoration of Diadromous Fishes to the ...

However, it was determined that northern pike dispersal in Sweden was precluded
only when maximum stream slope approached 6.6 % (Spens et al. 2007).
Dispersal
Emigration and immigration can play an important role in fish population dynamics,
however dispersal does not appear to be a significant population mechanism for the
northern pike (Craig 2008). They are mainly but not exclusively sedentary and do
not move far from a home range (Craig 2008). Northern pike that disperse or
migrate exhibit homing behavior as they generally returned to the same spawning
area the following year (Craig 2008). Females rather than males generally move
greater distances (Koed et al. 2006). However, the migration distances between
summer and spawning habitat are typically less than 2 kilometer and not more than
10 kilometers (J. Casselman, Queen’s University, personal communication,
February 11, 2009).
Potential Habitat Model
Abiotic factors, such as temperature and vegetation, on northern pike population
dynamics are well established (Craig 2008). Several of these factors were used to
develop a model of potential habitat for pike in the Piscataquis River watershed. A
model is a representation of a system or process that can be used to define a
problem, organize an approach, understand the available data and make predictions
(Starfield and Bleloch1986). Given that models are representations, they have
limitations based on the level of understanding one has about the issue and the type
of data that is available.
For northern pike, the scientific literature is well established and provides a robust
level of understanding. However, data on northern pike (and to some extent our
understanding) in Maine is limited. A model is one way to support management
decisions that will be made on the overall risk from northern pike when there is
uncertainty in our understanding or available data. The modeling approached was
based on examining the critical habitat criteria for northern pike discussed above,
developing indicators from the literature for representing the habitat criteria and then
applying the indicators to develop a combined measure of habitat potential.
Two potential habitat models were developed based on waterbodies (lakes and
ponds) and waterways (streams and rivers). The models are based on the factors
and measures that could be developed using existing information for the watershed
(Tables 4 and 5). The model results are representative of habitat conditions based
on the best available information and assume a positive relationship between habitat
conditions and the capacity for establishing resident pike populations. The results
are provided as a ranking (low, medium or high potential) for waterbodies and as a
value of 0 to 1 (0 being no or low suitability) for waterways.
Methods
Tables 4 and 5 describe the measures that were developed as critical habitat
parameters based on: 1) the literature on the habitat requirements of northern pike
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