Subject: ATOC MMRP results (fwd)

Mike Williamson (pita@www1.wheelock.edu)
Fri, 2 Jul 1999 09:51:26 -0400 (EDT)

Date: Wed, 30 Jun 1999 05:35:26 -0700
From: MARMAM Editors <marmamed@UVic.CA>
Reply-To: Marine Mammals Research and Conservation Discussion
     <MARMAM@UVVM.UVIC.CA>
To: MARMAM@UVVM.UVIC.CA
Subject: Re: ATOC MMRP results (fwd)

Forwarded message:
From: lweilgar@IS.Dal.Ca

As the ATOC project (Hawaii portion) personnel appear to want to
continue its broadcasts of loud low-frequency sounds over the Pacific
ocean basin, beyond the originally intended two years, we felt the
following information to be relevant:

        "Both humpback and sperm whales were generally seen farther
from the sound source during experimental [ATOC sound source on]
versus control [ATOC source off] surveys (p<0.05)."  This is a quote
from:
      Calambokidis, J., Chandler, T.E., Costa, D.P., Clark, C.W.,
and H. Whitehead. Effects of the ATOC sound source on the
distribution of marine mammals observed from aerial surveys off
central California.  In: Abstracts of the World Marine Mammal Science
Conference, 20-24 January 1998, Monaco, p. 22.

Despite these results, we continue to read on the ATOC web page the
following:
     "The sperm whale distribution data from the first year of
California aerial surveys did reveal an interesting trend.  The
average distance of all groups for experimental surveys was greater
than the distance during control surveys...An acoustic explanation of
the first year's results, based on a fairly simple analysis of mean
distances per survey, is not obvious.  It does not have a strong
causal linkage to acoustics since the expected received levels...for
the average experimental distance of 14 + 4 km are nearly identical
to the levels that would occur at the average control distance of 11
+ 5km."

From:
 (Marine Mammal Research Program: results from over a year of
acoustic transmissions, May 14, 1997, Adam S. Frankel and Chris
Clark, http://atoc.ucsd.edu).

And:

"Experiments conducted to date have found the sound transmissions
to be biologically innocuous, said Christopher Clark of Cornell
University's Bioacoustic Research Program.  For the past year and a
half, researchers have been conducting aerial surveys off the coast
of San Francisco to discern whether blue, humpback, or sperm whales
avoid the Pioneer Seamount-where the ATOC source is located-during
periods when transmissions occur.  Only a slight difference in the
distributions of sperm and humpback whales has been observed, and it
does not appear to be directly related to the sound level, Clark
said."

From:
 (Howard, Janet. 1998 (Fall). Listening to the ocean's
temperature. Explorations 5(2), 7 pp.).

     We would like to finally lay this misleading
interpretation to rest.  Even though the expected received sound
levels to the whales for the average control and average experimental
distances [from the sound source] are "nearly identical", this does
not mean that the effect is insubstantial.  What the ATOC researchers
(Frankel and Clark) appear to fail to address is the simple geometry
of a circle.  The average will be dominated by levels relatively far
from the sound source because, in a circle, the farther away from the
center you go, the greater the area.  As only a small difference in
average distance would be expected with substantial biological
effects, this argument is extremely misleading.
       For instance, if sperm whales were excluded from ranges up to
ONE THIRD of the radius of the study area, average distance is
increased by only 7%.  With sperm whales excluded from ranges up to
TWO THIRDS of the radius of the study area, average distance is
increased by only 27%, WHICH IS ABOUT THAT FOUND IN THE ATOC STUDY.
Again, to say that because the average received sound levels are
similar between control and experimental groups and that therefore
the effect is negligible is very misleading.  These "slight
differences" Clark and Frankel refer to, could represent (are
consistent with) whales clearing out of two-thirds of the radius of
the study area during ATOC transmissions.

      We have repeatedly pointed this out to the ATOC researchers and
would have more confidence in this study if these (above) statements
by the MMRP ATOC team were adequately clarified and the misleading
statements removed.  Of course, whether the avoidance by sperm
whales and humpback whales of the ATOC noise is "biologically
meaningful" is another question and one that is extremely difficult
to tackle, especially over the short term.  This is the main problem
plaguing the continued efforts of marine mammal scientists attempting
to study the effects of ATOC, LFA sonar, etc., and lays them open to
criticism of whether these studies (which themselves add more noise
to the environment) are really worthwhile.

Sincerely,
      Lindy Weilgart (Research Associate) and Hal Whitehead
(Professor)

Dept. of Biology
Dalhousie University
Halifax, Nova Scotia B3H 4J1  Canada


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