EPA's Vessel General Permit and Small Vessel General

serve as a protective buffer against predation.
� Freshwater and estuary migration sites with sufficiently cool water temperatures and
water flows that coincide with diurnal cues to stimulate smolt migration.
� Freshwater migration sites with water chemistry (particularly pH) needed to support sea
water adaptation of smolts.
These PCEs have undergone significant degradation over in the recent past. Dams, along with
degraded substrate and cover, water quality, water temperature, and biological communities,
have reduced the quality and quantity of habitat available to Atlantic salmon populations within
the DPS. A combined total of twenty FERC-licensed hydropower dams on the Penobscot River
significantly impede the migration of Atlantic salmon and other diadromous fish to historically
accessible spawning and rearing habitat. Agriculture and urban development largely affect the
lower third of the Penobscot River below the Piscataquis River sub-basin by reducing substrate
and cover, reducing water quality, and elevating water temperatures. Introductions of
smallmouth bass and other non-indigenous species significantly degrade habitat quality
throughout the mainstem Penobscot and portions of the Mattawamkeag, Piscataquis, and lower
Penobscot sub-basins by altering predator/prey relationships. Similar to smallmouth bass, recent
Northern pike introductions threaten habitat in the lower Penobscot River below the Great Works
Dam.
Today, dams are the greatest impediment, outside of marine survival, to the recovery of salmon
in the Penobscot, Kennebec and Androscoggin river basins (Fay et al. 2006). Hydropower dams
significantly impede the migration of Atlantic salmon and other diadromous fish and either
reduce or eliminate access to historically accessible spawning and rearing habitat. In addition to
hydropower dams, agriculture and urban development largely affect the lower third of the
Merrymeeting Bay recovery unit by reducing substrate and cover, reducing water quality, and
elevating water temperatures. Additionally, smallmouth bass and brown trout introductions,
along with other non-indigenous species, significantly degrade habitat quality throughout the
Merrymeeting Bay recovery unit by altering natural predator/prey relationships.
Impacts to substrate and cover, water quality, water temperature, biological communities, and
migratory corridors, among a host of other factors, have impacted the quality and quantity of
habitat available to Atlantic salmon populations within the Downeast Coastal recovery unit.
Two hydropower dams on the Union river, and to a lesser extent the small ice dam on the lower
Narraguagus River, limit access to spawning and rearing habitat within these two watersheds. In
the Union River, physical and biological features have been most notably limited by high water
temperatures and abundant smallmouth bass populations associated with impoundments. In the
Pleasant River and Tunk Stream, which collectively contain over 4,300 units of spawning and
rearing habitat, pH has been identified as possibly being the predominate limiting factor. The
Machias, Narraguagus, and East Machias rivers contain the highest quality habitat and
collectively account for approximately 40 percent of the spawning and rearing habitat in the
Downeast Coastal recovery unit.
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