Blue whales and seismic

From: Dagmar Fertl (dfertl@geo-marine.com)
Date: Tue Nov 18 2003 - 09:39:38 EST

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    Hi Dagmar,
    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
    discrepancy?

    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.

    Regards,
    HAZEL MACK
    ******************************************************
    Hazel,

    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
    downloaded offline):

    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
    ones.

    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
    (roger.gentry@noaa.gov). 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.

    Regards,
    Dagmar Fertl



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