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

In Maine, lake trout feed primarily on smelts. From 1985 to 2006, MDIFW staff
examined 593 lake trout stomachs from Sebec Lake. Smelts occurred in 61% of the
stomachs containing food and constituted 51% of the total volume of food items.
White perch were the next most important identifiable prey item occurring in 26% of
the stomachs with food and representing 26% of the total volume. From 1971-2006,
3,267 lake trout stomachs were examined from Moosehead Lake. Smelts were by
far the most important food item. Smelts occurred in 72% of the stomachs containing
food and represented 81% of the total volume of food. The next most important food
item was yellow perch, which occurred in just 4% of the stomachs containing food,
and represented 4 % of the total volume. Of the 20 other identified fish or
invertebrate food items in the sample, none exceeded 3% of the total volume.
Atlantic Salmon: Danie et al. (1984) provides the following summary of salmon life
history. Atlantic salmon ascend freshwater streams to spawn on gravel substrate
from mid-October to mid-November. In Maine, eggs incubate for 175 to 195 days
depending on water temperature, and hatch in April or early May. After hatching, the
15 mm long yolk-sac larvae (alevins) remain buried in the gravel depressions for up
to six weeks while absorbing the yolk-sac for nourishment. The resulting 25 mm long
fry begin foraging for themselves and emerge, usually at night, from the gravel
depressions. Larger freshwater juveniles (parr) will remain in riffle sections of
streams until they are 125-150 mm in length, which may take from two to three
years. Failure to attain this length by spring or early summer of the year will prevent
parr from transforming into smolts (seaward migrating juveniles). After attaining this
critical length, parr undergo smoltification, which includes physical and physiological
changes adaptive to a migration to a marine environment. The parr marks disappear
and the skin develops a silvery pigmentation from deposition of guanine in the skin,
the tail lengthens and becomes more deeply forked, and schooling behavior
develops. Increases in water temperature and water level trigger downstream
migration of smolts. Smolts from the western Atlantic migrate, within 3m of the
surface of the ocean, to feeding areas in the Davis Strait between Labrador and
Greenland. Atlantic salmon will return to natal rivers to spawn after one (grilse) or
two (bright salmon) years at sea. Salmon accumulate in estuaries, bays, and river
mouths, before ascending streams. Upstream migration of salmon coincides with
increases in water flow. Adult salmon do not feed while in freshwater. Atlantic
salmon do not consistently die after spawning, and many spent fish (kelts) survive
the winter in freshwater and begin to feed again. Mortality is high when kelts enter
saltwater. Those kelts that survive and migrate to feeding grounds in the Davis
Strait, may become repeat spawners. (From USFWS
(http://www.fws.gov/r5gomp/gom/habitatstudy/metadata/Atlantic_salmon_model.htm).
Risks to Native Species from Niche Overlap
Habitat in the mainstem of the Piscataquis River and the Sebec River are likely both
suitable for the establishment of resident pike populations (Figure 10). Both rivers
are stocked with spring and fall yearling brook trout. These fish are scattered
throughout the Piscataquis River from Abbot to East Dover, including into or near
many deadwater areas that would likely hold adult and sub-adult pike if they are
there. The Sebec River is stocked below the Sebec Lake Dam into run/pool habitat,
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