I work for an oil and gas company in Australia, and we're thinking about
drilling in deep water in the south of Australia. I've been assigned to
research the impacts of oil and gas activities-especially shooting seismic,
on Blue whales as we know that the area is inhabited by Blue whales for part
of the year.
Obviously, I'm keen to gather as much pertinent information as I can so that
we can make informed decisions and develop a sound environmental impact
assessment, not only for the whales but the entire offshore environment.
I've done a brief search on the web for information relating to the effects
of seismic on Blue whales and there doesn't seem to be too many studies
done. I was wondering if you could provide me with the titles of any
papers or any information that might be relevant to my research?
I've also noticed that the US National Marine Fisheries have a threshold
figure of 180 dB before any physical harm occurs to whales, yet in other
papers I've read this figure is 120 dB. Do you know why there is a
Any help you could give me would be greatly appreciated. There seems to be
so many papers to read but never enough time so I would like to read the
'relevant' ones. Hopefully you will be able to help, if not then I thank
you for your time and sorry to have inconvenienced you.
Wow, some questions I can really sink my teeth into. I'm getting some
serious flashbacks to my days with the Minerals Management Service (MMS).
I'm not as familiar with blue whale reactions to seismic as I am other
baleen whales, such as humpbacks, grays, and bowhead whales. I would suggest
looking at some of that literature. I'm just going to assume that maybe you
don't have all the available literature yet, so if you have a reference
already, that's super. I recommend that you obtain a copy of J. Richardson's
et al. 1995 "Marine Mammals and Noise" book. It is the bible for folks like
me who work on marine mammal/acoustic issues. Additionally, and this can be
downloaded from the web, get a copy of D. Ketten's 1998 NOAA Technical
Memorandum "Marine Mammal Auditory Systems...". I have one article in my
collection directly talking about blue whales and seismic (an abstract from
one of the JASA conferences):
McDonald, M. A., J. A. Hildebrand, et al. (1993). "Vocalizations of blue and
humpback whales during a midocean ridge airgun experiment." Journal of
Acoustical Society of America 94(3,pt 2): 1849.
Down your way, and you're probably familiar with this (and it can be
McCauley, R. D., J. Fewtrell, et al. (2000). Marine seismic surveys:
Analysis and propagation of air-gun signals; And effects of air-gun exposure
on humpback whales, sea turtles, fishes and squid. Bentley, Australia,
Curtin University of Technology, Centre for Marine Science and Technology.
Another good source of information for assessing environmental impacts to
cetaceans from seismic surveys would be to contact the MMS. I suggest Judy
Wilson (Judy.Wilson@mms.gov) who is their head protected species person. MMS
has written up EIS' for oil and gas exploration and production activities,
and information from various species can be applicable to the blue whale.
Additionally, MMS is in the process of working on an EA for seismic surveys.
Judy could provide you with more information on all of the before-mentioned.
Like I said, you should be interested in all baleen whale species reactions,
because all baleen whales are low-frequency vocalizers, and as a result,
should be hearing low-frequency sounds. As you know, airguns not only have a
low-frequency component, but also a high-frequency component. I assume
you're considering impacts to the small cetaceans as well as the larger
Last but not least for sources, contacting anyone in the U.K. associated
with seismic survey regulations would be good. Judy can also help you with
that (just tell her you talked to me).
As for the differences in the numbers associated with temporary threshold
shift, that's a bit trickier. That question would best be posed to the head
acoustics person at National Marine Fisheries Service, Dr. Roger Gentry
(firstname.lastname@example.org). My understanding (and remember I'm not an
acoustician and by no means an expert in anything of this stuff) is that we
are talking about different types of 'takes' in the U.S. The Marine Mammal
Protection Act (MMPA) sets forth a Level A take (serious injury or death)
and a Level B take (harassment, such as change in the animal's behavior).
Through lots of acoustic analysis work...and a leader in this discussion is
the EIS that was prepared for the Shocktesting of the Churchill). If you
don't have a copy of the FEIS for the Churchill, I highly recommend
obtaining it. Anyhow, the 180 dB comes from hearing tests of bottlenose
dolphins in a captive setting, conducted by the Navy's marine mammal
research program. This report (I think is still) available online. The 180
dB was the onset of a temporary shift in the hearing ability (temporary
threshold shift [TTS]) of the dolphins. It is the only measured information,
and scientists agreed that it would be the 'standard' for the TTS. Remember
that TTS refers to a 'recoverable' hearing loss. Kind of like when you go
listen to loud music, but later can still hear ok. The 120 dB is also a
Level B take, that NMFS is currently working on. It is 'sub-TTS'. It is the
dB level at which you start seeing behavioral changes in the animal. Does
that make sense? 120 dB is when you start seeing a reaction by the animals,
but 180 dB is when you actually start getting a shift in the hearing ability
of the animals. This recognizes that animals are already 'feeling
uncomfortable' with a certain level of sound, but it hasn't affected the
ears themselves. Anyhow, that's a quick and dirty explanation, and hopefully
correct. Like I said, it's something that is still being hammered out with
NMFS. NMFS does not have an official 'acoustic criterion' per se at this
point, but is working on it. It's a hard thing to do, b/c we can't
necessarily ask these animals when they are responding, and almost have to
arbitrarily come up with some numbers. Can you imagine setting up a hearing
test for a blue whale??
I am more than happy to try to help you more. As you can imagine, I've read
to nauseum about this topic, but more in terms of toothed whales, like sperm
whales and dolphins. I hope this information will be of some help though.
Let me know how it goes.
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