Effects from Other Human-Related Activities
Sound
In addition
to the sound generated by vessels, there are numerous other sources
of sound in the marine environment to which marine mammals are exposed.
A study conducted by Malme and Krumhansl (1993) to evaluate the effects
of noise associated with a tunnel boring machine used to construct the
new sewage outfall for the Massachusetts Water Resources Authority determined
that the machine produced sound at frequencies between 6.3 and 10,000
Hertz. Peak volumes of 120 - 130 dB were recorded above the boring machine
in about twenty feet of water. According to the biological opinion (NMFS,
1993a) conducted in accordance with the Endangered Species Act for this
project, sound generation with these characteristics is detectable by
cetaceans and may elicit some reaction. In this instance however, since
no sudden changes in the sound characteristics above ambient operation
levels were expected during routine operation of the boring machine,
it was not expected to cause harm to the endangered cetacean species
which were the subject of this evaluation.
Biopsy Darting
The reaction
to biopsy darting used for scientific research purposes for two species
of large cetaceans (northern right whale and humpback whale) indicates
an immediate, short-lived, minimal reaction, which varies among individuals
(Brown, et. al., 1991, Weinrich, et. al. 1991). Reactions were recorded
as minor changes in behavior and included twitching, swimming away,
arching the back, flicking the tail or lobtailing, and trumpetblows.
Although direct comparison of the studies is not possible due to the
different approaches used, it appears that humpback whales reacted more
frequently to biopsy darting than did right whales.
Predation
Although
little is known about the extent of predation on marine mammal populations
in the region, there is some evidence to suggest that smaller cetaceans
and pinnipeds are effected by a number of large predators including
white sharks and killer whales (Stobo and Beck, 1987 Brodie and Beck,
1983). In addition, some of the larger baleen whales, particularly humpback
whales included in the GOM photographic identification catalog, show
scarring patterns which have been attributed to attacks by killer whales.
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