Environmental Engineering Reference
In-Depth Information
habitat to support more fish), will have no overall effect (because it simply draws fish
from other, nearby areas), or will decrease fish populations (by facilitating harvest
by predators and fishermen). The determination of the effects of FADs at a particu-
lar location is complicated by the influence of non-independent factors: proximity
of other FADs (e.g., other wave energy units), interconnection of multiple FADs to
provide routes for the movement of associated fishes, and temporal dependence (the
number of fish present at one sampling date influencing the number at the next sam-
pling date due to fish becoming residents) (Kingsford, 1999). Statistical approaches
that could be applied to experiments on the effects of FADs on fish populations and
solutions to the independent factor problems were also described.
Because anchoring systems and mooring lines will likely exclude fishing activi-
ties, energy parks could serve as marine protected areas. The Pacific Fisheries
Management Council (2008) expressed concerns related to the prohibition of com-
mercial fishing at wave energy test areas and suggested that there may be either a
reduction in total fishing effort and lost productivity or a displacement of fishing
effort to areas outside the areas closed to fishing. Displaced fishermen would likely
concentrate their efforts in areas immediately outside the wave park boundaries,
resulting in increased pressures on fish and habitats in those nearby areas.
Floating offshore wave energy facilities could create artificial haul-out sites for
marine mammals (pinnipeds). Devices with a low profile above the waterline (desir-
able for aesthetic reasons) may enable seals and sea lions to use them as a haul-
out site, particularly if the installations attract the marine mammals by acting as
fish-concentrating devices. NOAA considers the creation of such artificial haul-outs
as undesirable and recommends the use of deterrents to discourage use by marine
mammals.
Floating devices could potentially impede movements of floating marine habitat
communities, such as
Sargassum
communities. Masses of floating
Sargassum
algae
form unique communities of organisms that serve as important habitats for hatchling
sea turtles and juvenile fish (Coston-Clements et al., 1991). Strong current from the
Sargasso Sea in the middle of the Atlantic Ocean carry these
Sargassum
communi-
ties around the world.
Floating devices with above-water structures may attract seabirds by creating
artificial roosting sites or encouraging predation on fish near the FAD (Michel et al.,
2007). There is particular concern about collision injuries to marine birds that are
attracted to lighted structures at night or in inclement weather (Boehlert et al., 2008;
Thompson et al., 2008). Peterson et al. (2006) monitored the interactions of birds
and above-water structures at a Danish offshore wind farm from 1999 to 2005 and
found that birds generally avoided the wind farms by flying around them, although
there were considerable differences among species. The monitoring data suggested
that avoidance was reduced at night. The authors obtained few data under condi-
tions of poor visibility because bird migrations slowed or ceased during such times.
Birds typically showed avoidance responses to the rotating wind turbine blades. A
stochastic model predicted very low rates of Eider collisions with the offshore wind
turbines, and the predictions were confirmed by subsequent monitoring (Petersen et
al., 2006). Desholm (2006) provided a series of papers that describe techniques for
predicting and monitoring interactions of birds and wind turbine structures at sea.
