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

spread of any invasive species, and has determined that, even if there were a risk of
spread, the benefits of the Penobscot River Restoration Project clearly outweigh the
potential harm. They further explain that the available information on northern pike in
the Penobscot River watershed does not indicate that it has caused economic harm or
harm to human, animal or plant health nor has it dispersed widely since its humancaused
introduction. The Service was involved in assisting to complete the northern
pike risk assessment and they stated that the additional measures to selectively control
and manage this introduction are feasible and prudent measures to minimize the risk of
harm.
The Service also explained that Section 2(2)(iv) of the Executive Order calls for the
restoration of native species and habitats to reduce the effects of invasive species and
to prevent further invasions. Consequently, they believe that this Plan and the elements
in Lower Penobscot River Multiparty Settlement Agreement are consistent with the
Executive Order because they are meant to restore diadromous fish to the watershed.
The State of Maine has developed an advisory list of over 80 invasive species that
includes northern pike (located in Appendix D of the State of Maine Action Plan For
Managing Invasive Aquatic Species), however the state has not gone as far as to
include pike in a regulatory definition of an invasive species as it has done with certain
aquatic invasive plants (Title 38: Chapter 3: Subchapter 1: §410-N. Aquatic nuisance
species control). In and of itself, the advisory list is not a regulation or law. The state’s
advisory list recommends selective control and management for Northern pike, which
have been implemented by the state and its partners for the population of northern pike
in Pushaw Lake and Mud Pond. The northern pike risk assessment provides additional
measures to selectively control and manage this introduction. The Action Plan notes, as
does the risk assessment, illegal introductions are the main pathway for this species.
The measures that the state has taken or are proposing to control pike are feasible and
prudent measures to minimize the risk of harm.
Comment: What is the projected time frame that the pike could make it up the river if the
barriers are removed?
Response: No data or methods were readily available to predict the rate of natural
dispersal of northern pike. We believe that the natural dispersal rate would be low
because of several life history traits:
1. Northern pike have a narrow optimum temperature range of between 19 and 21º
C. This temperature range is often exceeded in the summer months on the
mainstem rivers;
2. Northern pike are generally sedentary and do not move great distances (2
kilometers). This behavior has been documented in Pushaw Lake through radio
telemetry;
3. The greatest movement of pike occurs during the spawning period in early spring
and there is some indication in the literature that it may be related to a return to
natal spawning sites as opposed to dispersal to new sites;
4. Pike dispersal appears to be related to an increase in density. The density of
pike in Pushaw Lake appears to be low so we do not expect density-dependent
movement to occur in the near future;
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