Final Mitigated Negative Declaration and Response to Comments

mouth of Emerald Bay. Creating noise or visual disturbance during sensitive periods of the
breeding season could result in impacts to this species.
Osprey (Pandion haliaetus). The osprey is a TRPA threshold species. They are a migratory
species and are present during the breeding season, April 1 through August 15. They build
large stick nests in treetops or snags in open forests within fifteen miles of water used for
foraging (DFG 2008). Ospreys are known to nest in Emerald Bay SP, including near the
proposed project area. No habitat suitable for this species would be altered by project
activities; however, project activities during the breeding season could impact this species.
Ospreys have high nest site fidelity and selectively choose nesting locations with a clear view
of the surrounding area. Creating noise or visual disturbance during sensitive periods of the
breeding season could result in impacts to this species.
Great Basin rams-horn (Helisoma newberryi). This species is known to occur in Lake Tahoe.
These snails burrow into soft mud of larger lakes and slow rivers. The project area consists of
rock or cobble and there are no soft, muddy habitat types with slow moving water in proximity
to project activities. Because typically suitable habitat for this species does not occur in the
project area, impacts to this species are expected to be less than significant.
Lake Tahoe benthic stonefly (Capnia lacustra). This species is known to occur in Lake
Tahoe at depths of 95-400 feet. Project activities will not occur in deep water areas and will
not impact suitable habitat for this species.
Benthic invertebrates- Although these animals are not listed as sensitive species, the benthic
animal community in Lake Tahoe is an important component of the ecosystem. Whittmann et
al. (2011) found that benthic barriers resulted in 100% mortality to Asian clams (AC) after 28
days, and resulted in 70-95% of total macroinvertebrate diversity reduced. Most notable was
the less severe impacts to native species including the pea clam (Pisidium spp.), with no
significant impacts seen in one test plot. Lesser impacts to native macroinvertebrates would
potentially allow a pool for recolonization. While the barriers reduce diversity of native
macroinvertebrates in the short term, the alternative of allowing the AC populations to expand
would potentially exclude native macroinvertebrates from the larger system into the future.
The infestation in Emerald Bay has already expanded over 40% in size since the initial survey
in 2009. Treatment of approximately 5.5 acres out of the 870 (.6%) acres included in the
underwater park would result in less than significant short term impact to this community, with
potential substantial long term benefits.
Lahontan Cutthroat Trout (Oncorhynchus clarkia henshawi). Researchers are in the process
of reintroducing the Federally Threatened Lahontan cutthroat trout into Lake Tahoe and
Emerald Bay and monitoring survival and life history as well as providing a recreational fishery.
These fish are obligate stream spawners so deployment of benthic barriers is not expected to
impact potential spawning habitat. A combination of factors is presumed to have led to the
extinction of Lahontan cutthroat trout from Lake Tahoe, with the introduction of non-native
species perhaps being the primary factor. Asian clams are a non-native species that
negatively impact native species and removal of these clams from a target reintroduction area
is not anticipated to negatively impact reintroduced Lahontan cutthroat trout.
Asian Clam Control Project IS/MND
Emerald Bay State Park
California Department of Parks and Recreation
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