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

No improvements were made over the original model and weightings. The model
correctly classified 66% percent of the northern pike lakes rated by VanRiper, over
classified 17% of the lakes (the model predicted a higher potential than the rating),
and under classified 17% of the lakes (the model predicted a lower potential than the
rating). Overall, the model conservatively classified 83% of the lakes by classifying
them correctly or overestimating the lake potential (classifying a lake as medium that
VanRiper identified as low).
The five northern pike lakes that were under classified by the model were reviewed.
Lake areas > 1000 HA, mesotrophic lakes, lakes that stratefy and < 0.5 meters per
year of runoff from watershed are the parameters that most predicted the model's
under classified lakes in Region B (Ingham, Long, Great, Messalonskee and Little
North/North Ponds). However, the lake type (mesotrophic) may be more indicative of
lakes in Region B than Region F. Based on this screening criteria, at least three
lakes would need to be reviewed using best professional judgment: Silver, Upper
Ebeemee and Seboeis Lakes. They meet some but not all of the screening criteria.
Human Dispersal
Natural dispersal occurs at a lower mean rate (1.15 introductions per year) than
human-caused introduction (2.63 introductions per year). Human-caused
introductions are more likely to result in multiple introductions in one year than
introductions through natural dispersal. The probability of three or more
introductions in one year is 0.49 for human-caused introductions in contrast to a
probability of 0.11 for natural dispersal. This higher probability may arise from the
mechanism of dispersal. Human-caused introductions can occur through a
watershed in watersheds that are disassociated from those that contain northern
pike. Introductions through natural dispersal occur in watersheds where pike are
found and more likely to occur in habitat adjacent to or downstream of existing
populations (J. Casselman, personal communication, March 13, 2009).
Both pathways pose a risk for introduction of northern pike, however human-caused
introductions pose a greater risk. They have a very low probability of resulting in no
introductions in any one year, they have a much higher mean rate of introduction,
they have a much higher probability of multiple introductions in one year, and they
can result in introductions in watersheds removed from those watersheds with
populations of northern pike.
Summary of Resources at Risk
In order to determine the extent of resources at risk above Howland, two approaches
were taken: identifying priority resources and associated geographic locations areas
throughout the drainage, and barriers to northern pike, both natural and
anthropogenic.
A list of five priority resources was developed. High priority resource classes
include: high quality brook trout habitat, wild landlocked salmon, lake trout or brook
trout lakes, species of Concern (Lake whitefish in Hebron Lake, arctic char in Bald
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