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

Adult landlocked salmon, both wild and hatchery origin, can occur in a wide range of
lake types including: oligotrophic, mesotrophic, and even a few homothermous
waters. Salmon prefer cool, well oxygenated water but can exist in less favorable
conditions. Adult salmon are generally located in the thermocline in the summer
months if stratification occurs. They can frequently be found in the pelagic areas of
these lakes. In the winter months, salmon are found not only suspended over
deeper areas, but also in the littoral areas of lakes. Location of forage fish, primarily
smelts, will often dictate the location of adult salmon. In the West Branch of the
Penobscot River, adult salmon overwinter in large deadwaters in the lower reaches
of the river. Spear (in FERC Project No 2572, 1991) found that the most important
overwintering deadwaters contained low velocities, shallow bays and logans, and
muddy substrate.
Food habits of YOY salmon were examined during the relicensing of the Ripogenus
Dam in Maine. Data collected by Great Northern Paper Co., Inc were presented in
Warner and Harvey (1985). These young salmon were feeding primarily on insects
including Ephemeroptera , Diptera, and Tricoptera. There is a paucity of information
of the food habits of salmon parr although it is likely they feed similarly on insects.
Adult landlocked salmon also feed on aquatic insects during summer months.
However, smelts are considered the primary food source for adult salmon. Warner
and Harvey (1985) details the importance of smelts for salmon growth and survival.
Smelt populations are notorious for wide fluctuations in density, which frequently
results in poor growth for salmonids. Alternative food sources, such as landlocked
alewives, have been established in some salmon waters. In Echo Lake, smelt
growth suffered after the introduction of landlocked alewives (Warner and Harvey
1985). Many of Maine’s tailwater river fisheries for landlocked salmon also benefit
from smelt drift from impoundments upstream, which helps to sustain salmon growth
in the river population. Spear (in FERC Project No 2572, 1991) estimated the
average total annual discharge of smelts into the West Branch of the Penobscot
River through the Ripogenus Dam from 1985 to 1989 to be 27,683 lbs. This section
of river is managed for trophy landlocked salmon.
Lake trout: Lake trout thrive in oligotrophic lakes. In the summer months they are
typically found in the hypolimnion and they prefer temperatures around 10 o C (Scott
and Crossman 1973). In the winter they can be found at any depth. During the
spring months, before stratification occurs, lake trout are often found in the littoral
zone. They can be occasionally found in larger tributaries to lakes in the spring,
especially during periods when smelts are spawning. In Maine, young lake trout are
found in the deepest basins (> 30m) during the summer months. Lake trout spawn
on rocky shoals and shorelines in mid to late October in Maine. The eggs are
scattered amongst the rocks and settle in the crevices, where they overwinter.
Water depth over egg deposition may vary, but Auclair (1985) states that lake trout
eggs were deposited in approximately one meter of water on shoals in Moosehead
Lake. Subsequent work on Moosehead Lake supports Auclair’s findings.
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