Environmental Engineering Reference
In-Depth Information
i
nTerFerenCe
WiTh
M
igraTory
a
niMals
The numerous floating and submerged structures, mooring lines, and transmission
cables associated with large ocean energy facilities could interfere with the long-dis-
tance migrations of marine animals (e.g., juvenile and adult salmonids, Dungeness
crabs, green sturgeon, elasmobranchs, sea turtles, marine mammals, birds) if they
are sited along migration corridors. On the U.S. Pacific Coast, effects on gray whales
(
Eschrichtius robustus
) may be of particular concern because they migrate within
2.8 km of the shore line. Boehlert et al. (2008) noted that buoys attached to com-
mercial crab pots already represent a major existing risk to gray whales off the coast
of Oregon. Lines associated with lobster pots and other fishing gear are a source of
injury and mortality to endangered North Atlantic right whales (
Eubalaena glacia-
lis
) on the East Coast of the United States (Caswell et al., 1999; Kraus et al., 2005).
Many marine fish species drift or actively migrate long distances in the sea and may
interact with ocean energy developments. Anadromous fish (e.g., green sturgeon,
salmon, steelhead) and catadromous fish (e.g., eels) migrate through both rivers and
oceans and therefore may encounter buoy hydrokinetic devices in the rivers and
ocean energy projects (Dadswell et al., 1987).
Entanglement of large, planktonic jellyfish with long tentacles (as well as actively
swimming sea turtles and marine mammals) is a potential issue for energy technolo-
gies with mooring lines in the pelagic zone. Thin mooring cables are expected to be
more dangerous than thick ones because they are more likely to cause lacerations
and entanglements, and slack cables are more likely to cause entanglements than taut
ones (Boehlert et al., 2008).
Michel et al. (2007) observed that smaller dolphins and pinnipeds could easily
move around mooring cables, but larger whales may have difficulty passing through
an energy facility with numerous, closely spaced lines. Marine species with propor-
tionately large pectoral fins or flippers may be relatively more vulnerable to mooring
lines, based on information from humpback whale entanglements with pot and gill
net lines (Johnson et al., 2005). Boehlert et al. (2008) suggested that whales prob-
ably do not sense the presence of mooring cables and as a result could strike them or
become entangled. In addition, they believed that if the cable density is sufficiently
great and spacing is close, cables could have a “wall effect” that could force whales
around them, potentially changing their migration routes. Whales and dolphins trav-
eling or feeding together may be at a greater risk than solitary individuals because
“ground response” may lead some individuals to follow others into danger (Faber
Maunsell and Metoc, 2007).
Wave energy converters deployed near sea turtle nesting beaches have the poten-
tial to interfere with the offshore migration of hatchlings. Interference with migra-
tion could occur if the energy project acts as a physical barrier or alters wave action,
which has been demonstrated to guide hatchlings away from the beach toward the
open ocean (Goff et al., 1998; Lohmann et al., 1995; Wang et al., 1998).
Some marine fish species form spawning aggregations at specific sites or times
(Coleman et al., 1996; Crawford and Carey, 1985; Cushing, 1969; Domeier and
Colin, 1997; Sinclair and Tremblay, 1984). Smith (1972) reported a spawning aggre-
gation consisting of 30,000 to 100,000 Nassau groupers (
Epinephelus striatus
) in the
