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Effect of Underwater Acoustics on Whales.

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Introduction

Effect of Underwater Acoustics on Whales

Biology 220W

Leah Kim

Student ID # 207740335

Section# 001


Abstract:  

Whales utilize acoustic frequencies to communicate underwater. If the whales are unable to communicate their bi-annual migration can become perilous.  Man-made low frequency sonar can prevent whales from producing sound and sometimes causes them to take alternate routes.  When the whales try to avoid the sonar they are in danger of running ashore and perishing after being beached.

Introduction:

Twice a year, around the months of December and May, populations of gray whales migrate from Mexico to Alaska. (Unknown1, 2002)  During this journey, they pass the state of California, where acoustical pulses, generated by air guns or water guns, are used in seismic surveys.  If the seismic-generated sound waves exceed the "background" noise or normal amount of noise, they could interfere with gray whale communication or disturb behavior. (Unknown1, 2002)  It is possible that seismic surveys have a detrimental impact on marine life, such as gray whales.

        Whales are able to perceive sound in a wide range of frequencies from 75 Hz up to 150 Hz.  In experimental conditions, where the environment’s level of noise is controlled, the whales are more sensitive and hear from 10 Hz to 100 Hz.  In addition, smaller whales have a broader range from which they can hear from 10 up to 300Hz. (Unknown2, 2002)

        Whales depend on sound for communication, navigation, and even detection of predators and prey.  The seismic-generated sound waves may disturb critical abilities.  Disruption of any of their vital functions can significantly disturb the fitness of whales. (Unknown3)

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Middle

Sonar is a general term applied to equipment and associated software that receives and possibly transmits sound.  Generic sonar samples the water by sending short single or repetitive pulses of sound from a point source down into the water, up from the bottom or across a body of water.  (Horne, J.K. 2000)  

One of the most recognized underwater sounds that have a significant effect on whales is Low Frequency Active Sonar (LFAS).  LFAS is an under water military system that the U.S. Navy created to detect “quiet” submarines.  The LFAS involves projecting an extremely loud low frequency sound into the ocean and then listening for the echoes.  This sound is produced at incredibly powerful levels making sound waves travel greater distances in the ocean.  This sonar is operated at 230 to 240+ dB. (Unknown4, 2001)  

In 1998, many legal cases against the use of LFAS were brought to public attention.  Some examples are Humpback whale calves separated from their mothers and a snorkeler was exposed to the LFAS and hospitalized as an acute trauma patient. (Unknown 4, 2001) The Navy terminated the LFAS tests and convinced the judge to dismiss the remaining cases because the research was complete.  In 2000, a permit was given to a doctor by the name of Dr. Peter Tyack to conduct more research on LFA that permitted him to harm the whales to a higher degree than cases from 1998.  The Federal Notice

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Conclusion

References Cited:

Unknown1. (2002) “Possible Effects of OCS Gas and Oil Activities on the California Gray Whale.” [Online] Available. http://www.mms.gov/omm/pasific/enviro/graywhale.htm

Unknown2. (2002) “Guidelines on minimizing acoustic disturbances to marine fauna.” [Online] Available. http://www.dme.wa.gov.au/pertroleum/pdf/envsheetmar02.pdf

Unknown3. (Year unknown) “Effects of Human-made sound on the Behavior of Whales” [Online] Available. http://birds.cornell.edu/BRP/humanmadesound/html

Unknown4. (2001) “Frequently Asked Questions about Low Frequency Active Sonar (LFAS)” [Online] Available. http://www.oceanmammalinst.org/faq-lfa.html

Unknown5. (2003) Seismic Exploration. [Online] Available. http://www.wdcs.org/dan/publishing.nsf/alweb/6b7d8fd1bab453f4802568ff004b9189

Unknown6. (2002) Federal Register Volume 67, No. 136 Rules and Regulations

Frantzis, A. (1998) does acoustic testing strand whales? Nature 392:29.

Gerrow, E.  (2002) “Mammalia Cetacea Baleniopteridae”) [Online] Available. http://members.fortunecity.com/anemaw/missionstatement.htm

Horne, J.K. (December 2000) “Acoustic approaches to remote species identification: a review” Fisheries Oceanography. Volume 9 Issue 4 Page 356

Malme, C.L Miles, P.R., Miller, G.W., Richardson, W.J., Roseneau, D.G., Thomson, K.H., and Green, C.R., (1989) Analysis and ranking of acoustic disturbance potential of petroleum industry activities and other sources of noise in the environment of marine mammals in Alaska. BBN Report 6945, OCS Study MMS 98-0006, Report from BBN Systems & Technological Corporation, Cambridge, MA, for US Minerals Management Service, Anchorage, AK, NTIS PB90-188673.

Richardson, W.J., Greene, C.R., Malme, C.I. and Thomson D.H., (1995) Marine Mammals and Noise. Academic Press

Simmonds, M.P. and Hutchinson, J.D. (1996) the Conservation of Whales and Dolphins. John Wiley & Sons

Sinkin, L. (2001) “U.S. Navy’s Low Frequency Active Sonar Research Exposed.” [Online] Available. http://www.whales.org.au/news/tyack.html

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