REGARDING THE MANATEE 8/17/2003

CAPTAIN TOM McGILL, P. E.

254 Sykes Point Lane Merritt Island, FL 32953-3067 Tel.: 321.453.1218, Fax: 321.453.3897, Cell: 321.917.2782

Email: capttom@cfl.rr.com

Regarding The Manatee,

The Best Available Science Says:

1. Manatees have great difficulty hearing below 400 Hz. Slow Boats make low frequency noise, and usually the larger the boat / propeller, the lower the frequency. (Documented Science Reference)

2. Manatees hear best at 12-18 KHz, but can hear up to 46 KHz. (Documented Science Reference)

3. Manatees hear pulsed sounds/noise better than continuous sounds. (Documented Science Reference)

4. Manatees have great difficulty seeing in most of Florida's turbid / murky waters. (Documented Science Reference)

5. The propellers are the primary noise source from watercraft after they attain a speed of a few MPH. For large ships at slow speeds, other noises such as engine noise can be detected, as propeller noise does not mask these sounds. Normally, the larger the vessel and propeller(s), the lower the frequency. (Documented Science Reference)

6. Manatees cannot hear a slow moving vessel (~ 4 MPH) until it is ~2 seconds or 12 feet away from collision. (Documented Science Reference)

7. Manatees can hear a planing vessel (~ 24 MPH) ~ 16 seconds or 560 feet away. The time and/or noise depend on the vessel type. Propeller tip velocity is a better indicator of noise power than vessel speed. The noise power is proportional to the 5th power of the tip velocity or approximately vessel speed raised to the 5th power! For this reason, masking of slow boat sounds by faster ones presents a serious problem. (Documented Science Reference)

8. Manatees do not generally inhabit waters that are less than 1 meter in depth. (Documented Science Reference)

9. Manatees will generally feed in shallow waters of less than 1meter only if near / adjacent to a deeper channel. (Documented Science Reference)

10. Manatees are capable of being trained and learning from experience. (Documented Science Reference)

11. Manatees can move with a burst of speed short distances at 21 feet/sec. or 14+ MPH. (Documented Science Reference)

12. Manatees can sustain speeds of 4-5 MPH for extended periods. (Documented Science Reference)

13. Manatees cannot hear the propellers of an approaching Tug that is pushing a Barge because the Barge creates a "sound shadow" forward of the Barge depending on depth of the water. The "spreading loss" of the acoustic energy from the propellers to the bow of a 100-meter long Barge-Tug combination is 100 db. Additionally, The Lloyd's Mirror Effect (out of phase sound wave cancellation) causes a large loss of low frequencies that could diffract around the Barge. (Documented Science Reference)

14. Manatees may not detect large ships because many ships have their propellers above the keel level, and the noise is projected from the ship's stern, thus producing an acoustic shadow in front of the ship. (Documented Science Reference)

15. Manatees infrequently vocalize. Mothers and calves seem to vocalize the most. (Documented Science Reference)

16. Manatees with propeller wounds or scars can be examined / measured to determine the general type of vessel and size of propeller involved as well as the direction of travel of the vessel. (Documented Science Reference)

17. Manatees as warm-blooded mammals are subject to hypothermia. (Documented Science Reference)

18. Manatees seek out warmer waters when the water temperature drops below 680 F. (Documented Science Reference)

19. Manatees historically spent the winter in areas south of Sebastian Inlet on the Atlantic coast until power plant and sewage plant warm effluents became available. (Documented Science Reference)

20. Manatees have been encouraged to artificially extend their winter range to regions well north of their historical limits by the discharge of thermal pollution into their environment from industrial sources. Some manatees no longer migrate due to the availability of such warm outlets. (Documented Science Reference)

21. Manatee total population has steadily increased as indicated by minimum population counts and increased total mortality since 1974 when such statistics were first recorded, recognizing that weather conditions can significantly affect any count. (Documented Science Reference)

22. Manatee population net average growth rate over the past 25 years has been ~ 6% per year after considering mortality from all causes. (Documented Science Reference)

23. Manatee mortality increase is consistent with an increasing manatee population. (Documented Science Reference)

24. Manatee mortality increase due to watercraft-related, if normalized (as a % of total), shows while there is variation with time, the average % trend line is flat. (Documented Science Reference)

25. Manatee species is not endangered, and any forecast of significant reduction in population over the next 50-100 years is driven by the discontinuation of the warm effluents at industrial plants and not due to other human related causes. (Documented Science Reference)

26. Manatee Slow Speed Zones have no effect on Barge-Tug operation because those vessels already operate at slow speeds in accordance with 68C-22.002, thus such zones do not reduce manatee mortality from collisions with Tug-Barges. (Documented Science Reference)

27. Manatee watercraft-related mortality comparison for several years before and after the implementation of a slow speed zone should be used to determine the effectiveness of such zones. (Documented Science Reference)

28. Manatees, if they have sensory awareness of on coming vessel(s), have the motivation and capability to evade the vessel(s), given a reasonable response time window, much better than a vessel operator who is dependent on active sensors to detect manatees and respond in that same time period. (Documented Science Reference)

29. Manatee protection could be significantly enhanced by the application of optimally tuned acoustic transmitters on vessels that operate in manatee-inhabited waters. (Documented Science Reference)

30. Manatees would have increased response time available to avoid collision with vessels if all vessels were required to transmit focused low-energy pulsed noise signals underwater immediately in front of the vessels' path in the manatee's best hearing frequency band. (Documented Science Reference)

Attached are references (by the paragraph #) for each of the above statements. Persons interested in a basic understanding of the manatee's hearing capability, environmental and acoustic considerations, and the reason why manatees and vessels collide are encouraged to read the very informative article entitled, Manatees, Bioacoustics and Boats, which was published in the American Scientist of March-April 2002 and can be reviewed on line at: www.americanscientist.org/articles/02articles/Gerstein.html, then click on "Go to Article."

The Best Available Science provides the ability to explain what, how, why, and to what extent natural phenomena occur based on current knowledge, not conjecture or unsubstantiated opinions, and it does not always validate popular opinion or even the intuitively obvious.

Captain Tom McGill 8/12/03

at capttom@cfl.rr.com

References

1. & 2. Gerstein, E., Gerstein, L., Forsythe, S. and J. Blue (1999) "The underwater audiogram of the West Indian manatee (Trichechus manatus), Journal Acoustical Society of America Vol. 105, No. 6, pp. 3575-3583.

3. Gerstein E., Gerstein L., Forsythe S., and J. Blue (2001) "It's all about SOUND Science: Manatees, masking and boats. Journal of the Acoustical Society of America 110: 2722.

4. Handbook of Marine Mammals, Volume 3, edited by Sam H. Ridgway and Sir Richard Harrison, 1985 (Hartman, 1971), page 53

5. Ross, Donald, "Mechanics of Underwater Noise," Pergamon Press, New York (1976).

6. Gerstein, E. R., Manatees, Bioacoustics and Boats, American Scientist, April 2002, vol 90, pages. 154-163

7. Gerstein, E. R., Manatees, Bioacoustics and Boats, American Scientist, April 2002, vol 90, pages. 154-163; and Ross, Donald, "Mechanics of Underwater Noise," Pergamon Press, New York (1976).

8. & 9. The Florida Manatee, by Victoria Brook Van Meter, revised 2001, Habitat page 5; Reynolds, John E. III and Odell, Daniel K., Manatees and Dugongs (1991), page 36.

10. Gerstein, E., Gerstein, L., Forsythe, S. and J. Blue (1999) "The underwater audiogram of the West Indian manatee (Trichechus manatus)", Journal Acoustical Society of America Vol. 105, No. 6, pp. 3575-3583.

11. & 12. Handbook of Marine Mammals, Volume 3, edited by Sam H. Ridgway and Sir Richard Harrison, 1985 (Hartman, 1971): Swimming and Diving, page 54-55. The Florida Manatee, by Victoria Brook Van Meter, revised 2001, Locomotion, page 14.

13. & 14. Gerstein, E (2002) "Manatees, Bioacoustics and Boats" American Scientist, vol. 90, pg. 154 –163.

15. Reynolds, John E. III and Odell, Daniel K., Manatees and Dugongs (1991), pages 40 and 41.

16. James Wood, A Simple and Effective Method for Analyzing Propeller Marks on Manatee in Brevard County, Florida, USA, August 15, 2001. Go to:

http://www.lumatrex.com/ASimplePropMethodforBrevard.htm

17. & 18. Thomas J. O'Shea, Bruce B. Ackerman, and H. Franklin Percival, Information And Technology Report 1, August 1995, Population Biology Of The Florida Manatee.

19. Moore, J. C., (1951), The Range of the Florida Manatee, in Quarterly Journal of Florida Academy of Sciences 14: 1-19.

20. & 21. Thomas J. O'Shea, Bruce B. Ackerman, and H. Franklin Percival,

Information And Technology Report 1, August 1995, Population Biology Of The Florida Manatee.

22. - 24. Thomas H. Fraser, Manatees in Florida: 2001, March 2001. Go to: http://ccaflorida.org/updates/Mar26_manatee.htm

25. Michael C. Runge, A Model for Assessing Incidental Take of Manatees Due to Watercraft-related Activities, attached as Appendix I to "Final EIS, Marine Mammal Protection Act-Florida Manatees," as Noticed in Federal Register/Vol. 68, No. 65/ Friday, April 4, 2003/Notices; Florida Fish and Wildlife Conservation Commission-Florida Marine Research Institute, Report on "Final Biological Status Review of the Florida Manatee (Trichechus manatus latirostris)," December 2002. Go to: http://floridamarine.org/engine/download_redirection_process.asp?file=manatee_bsr_2002_5008.pdf&objid=19139&dltype=article

26. Gerstein, E (2002) "Manatees, Bioacoustics and Boats" American Scientist, vol. 90, pg. 154 –163.

27. Florida Fish and Wildlife-Bureau of Protected Species Management, Brevard Watercraft Mortality Pre and Post-Speed Zone Postings, April 26, 1994, unpublished draft study. Go to www.cfwbrevard.org and click on "Information."

28. - 30. Gerstein, E., Gerstein, L., Forsythe, S. and J. Blue (1999) "The underwater audiogram of the West Indian manatee (Trichechus manatus)," Journal Acoustical Society of America Vol. 105, No. 6, pp. 3575-3583.