McGill's Rebuttal to FWC Paper

Rebuttal to Scott Calleson and Kipp Frohlich's paper entitled, "Slower boat speeds reduce risks to manatees" by Tom McGill

Preface

Scott Calleson and Kipp Frohlich recently authored a paper entitled, "Slower boat speeds reduce risks to manatees." Both Scott and Kipp are on staff at the Florida Fish and Wildlife Conservation Commission (FWC) in the Imperiled Species Management Section and have as their primary responsibility the task of promulgating rules, i.e., speed zones throughout the state of Florida. Currently, more than 22% of all manatee inhabited waters in Florida are restricted at slow or less speed. In Brevard and Lee Counties, home for a large portion of the manatee population, the percentage of restricted waters is more than 33%. Even so, the average watercraft-related manatee mortality has not been reduced. Accordingly, it is entirely reasonable to question the effectiveness of slow speed zones. It should not come as a surprise that Scott and Kipp firmly believe that slowing vessels down reduces the risk of vessel-manatee collisions because if it doesn't then Scott and Kipp have spent the past two decades wasting the taxpayers money and even worse, not properly looking out for the manatee species as is their duty or for that matter boaters. Boaters, fishers, and water sports enthusiasts have a keen interest in protecting the natural marine resources including the manatee, but they want to do so with large doses of good science and common sense. Unfortunately, FWC biocrats Calleson and Frohlich have offered little empirical scientific evidence but in its place offered lots of rhetoric and unsubstantiated claims. What follows is a rebuttal to their paper.

Abstract

Two FWC biologists authored a paper under the auspices of Endangered Species Research that addressed the merits of speed zones to reduce the risk of vessel-manatee collisions. They state that they believe slowing vessels down reduces the risk to manatees in 3 primary ways: (1) greater reaction time available for the vessel operator, (2) greater reaction time available for the manatee, and (3) reduced severity in the event the manatee is hit by a vessel. All 3 of these conditions are expressed as "beliefs" without any substantiating empirical data. Scientific papers are usually predicated on other than beliefs. Usually some data is provided to support the hypotheses. The authors reviewed some recent technical papers without any in depth discussion or explanation of why they accept some conclusions but rejected others. They conclude that, "The available information supports the position that reducing boat speeds in specific areas is an appropriate, reasonable, and defensible management action." This conclusion was reached without technical assessment of empirical data but rather simply based on the "beliefs"of the authors and their cherry picking of available research. Whenever scientists express their beliefs in place of providing substantiating empirical data that usually means they don't have any.

Introduction

The best way to address the paper in question is to do it point by point. First, the authors cite 3 primary ways they believe the risk to manatee is reduced by slowing vessels down:

(1) More reaction time for the boater: Certainly, if the vessel operator could see the manatee forward of his vessel's path he or she could take appropriate evasive action. However, in the normally murky waters of Florida (except at springs) the vessel operator has a low probability of sighting a submerged manatee even though manatees just below the surface often put out a tell tale sign/disturbance on the water surface. The vessel operator would have to have much more information to insure that he or she could reliably avoid such collisions in murky waters. Anyone who has spent a significant amount of time in manatee inhabited waters would recognize that reality.

(2) More reaction time for the manatee: If one understands and accepts the research findings of Dr. Edmund Gerstein, then the basic limitation of the manatee to hear low amplitude and low frequency noise in any significant background noise environment makes it very improbable that a manatee can use the "additional time for reaction" because it won't be aware of the oncoming vessel. The simple fact is the manatee cannot normally detect a slow moving oncoming vessel in murky waters until it is upon it which is often too late. The authors noted that Gerstein was currently conducting tests in the North Banana River. They would be well advised to review his research detail findings instead of ignoring the conclusions and obvious implications of his research.

(3) Reduced severity of injuries if a manatee is hit by a boat: It is true that impact by a small slow moving boat is less than if the boat were moving fast; however, that is not true if propeller contact is involved. If a large vessel (>39') is involved contact with the propeller can be fatal at any speed. In the case of very large vessels including barges, such an impact collision can easily be fatal. Interestingly, both Rommel and Wood indicated that such large vessels were disproportionately responsible for a higher percentage of such propeller wounds.

The important point in all of this discussion is the manatee relies on acoustical cues and has difficulty detecting slow moving vessels in murky waters and slow moving vessels emit lower amplitude and lower frequency noise. Thus, the intuitive solution of slowing down vessels to reduce risk to the manatee in murky waters is simply wrong. Science is based on much more than intuition. Gerstein's research provides the empirical data that fits with the acoustical science, his measured audiogram of the manatee, and offers an explanation for why some manatees have many scars from vessel collisions. It is this point that Calleson and Frohlich either don't comprehend or refuse to do so for political reasons. Understandably, if they accept that manatees rely on acoustical cues in murky waters they must then question their own past management actions of promulgating more and more slow speed zones. The Data

Tom McGill in his paper entitled, "A Macro Level Approach to Evaluate the Effectiveness of Slow Speed Zones in Protecting the Florida Manatee from Collisions with Watercraft," provided to FWC an analysis based on a table of its own data in June 2007. The Table 1 (see attached) contains all the recorded manatee mortality data since data collection started in June of 1974 through all of 2006. In addition to the State level data, the two counties with the largest manatee population were also included for all causes of manatee mortality. Brevard and Lee County account for about 36% (2,186/6,142) of all the manatee mortality and approximately 32% (473/1,478) of the watercraft-related mortality. Both Lee and Brevard Counties have ~ 33% of their waters regulated at slow or lower speed while the overall State has ~22%.

Table 2 (attached) shows the watercraft-related mortality data from 1986 through 2006 and the years in which there were significant red tide deaths. This permitted removal of the red tide data in order to compare data without the bias in those years. That table also compares the average watercraft-related percentage for 3 time periods in which there were different levels of waterway regulation. All three periods show an average of 26 % with the red tide mortality removed.

Slow speed zones have not been effective because the average percentage of watercraft-related mortality hasn't reduced after all those zones had been implemented for some time, and remember that was the original intent of the slow speed zones?

The average watercraft-related mortality percentage remained relatively constant in spite of a period that included reduced vessel registrations yet rising watercraft-related mortality after slow speed zones were implemented. Why do the authors ignore this point? How can they say that slow vessels reduce the risk to manatees when the empirical data, normalized to make it independent of manatee carcass recovery rate and manatee population, shows that such zones in the aggregate have not reduced the average percentage of manatee mortality caused by vessels? How can a scientific paper that is dedicated to showing how speed zones reduce manatee mortality ignore the statistics in the manatee mortality database?

The authors cite the work of several different researchers who made observations that manatees could detect vessels much farther than Gerstein indicated. The variance in methods, criteria, and subjective observations may be the basis for this difference. For example, Gerstein employed calibrated hydrophones in his experiments to determine the exact acoustical levels involved. At least 2 of the other cited studies were based on observations that the manatee reacted or didn't react to vessels when there was no empirical acoustical data to determine such a conclusion. One of the videos alleged to support manatee reaction to slow moving vessels, but there were no calibrated data other than the opinion of the observer as to why the manatee moved or didn't move and that is completely subjective. In Weigle's video, it is clear that in one instance a manatee didn't react to a slow vessel and would have been hit if the vessel course was not diverted. In another case three manatees were not responding to an idling boat approaching them and didn't react until the vessel operator throttled up thus dramatically (step function) changed the acoustics involved. In the Nowacek tests there was no calibrated sound reference involved to properly measure the acoustic noise levels and the conclusions were again primarily subjective. Also, a large percentage of the test runs were edited out of consideration. Most scientists understand that subjective data is always trumped by empirical data in such matters.

Manatee researchers who do not address the manatee's basic hearing limitation discovered and documented by Gerstein ignore the paramount scientific reason for vessel-manatee collisions. It is the underlying explanation for the cause-effect involved in manatee watercraft-related mortality. Manatees are well able to learn from their life experiences, and they can exhibit impressive bursts of speed (21'/sec) when alerted to a danger. Why then would a manatee have a large number of propeller scars resulting from multiple encounters with propellers? The most probable answer is that the manatee is repeatedly surprised by the offending vessels because it cannot detect and locate them. Unfortunately, those biologists involved in manatee protection and research have failed to capitalize for whatever reason on Gerstein's unique research findings.

The paper's authors further stated that it was their intent "to discuss the primary opposing views that have been raised against requiring slower speeds." However, where in their paper did they address the fact that the average watercraft-related mortality percentage has not been reduced? They only state that it has varied from a low of 11.4% and a high of 34.2%. They fail to discuss how the average watercraft-related mortality has changed because it hasn't! They also fail to note the reasons for a change in watercraft-related percentage. For example, in 1996 the watercraft-related mortality percentage was the lowest (14%) over the past 20 years but that was because there were so many red tide mortalities that year (>151), and when the red tide deaths are removed the watercraft-related percentage was 23% which only varies -3% from the average. Thus, without removing special events such as red tide deaths the watercraft-related mortality can appear to vary widely, but it actually doesn't. The extremes with red tide removed are shown in table 2 as a low of 21% and a high of 34% with an average of 26% from 1986 through 2006. Again, the important point is that average has not been reduced by speed zone implementation.

Chart 1 attached shows how the watercraft-related mortality has varied over the past 33 years as a percentage of total manatee mortality. The years that show a higher value of total mortality also reflect a lower percentage for watercraft-related mortality. This is primarily because of red tide events as previously discussed. The important point is to notice the flat trend line for the watercraft-related percentage. If the speed zones were effective in reducing such mortality then that trend line should show a significant downward slope which it does not indicate. The slope of the trend line over the past 33 years is -0.0001 which essentially means no change in the average.

The table of 21 known vessel strikes shown in the subject paper was used by the authors to show that most were not traveling at slow speed which they believe somehow bolsters their case that slow speed vessels are not responsible for most manatee strikes or deaths. The interesting thing is that ~ 40% of the 21 vessels were large vessels, i.e., > 39' LOA.

The authors enumerate the various vessels in the known vessel strikes or witnessed events table and conclude that any vessel size can injure or kill a manatee but then argue against the fact that the database and witnessed events indicate that large vessels are involved in a disproportionately high percentage of manatee mortalities.

In their tutorial on Newtonian theory they point out correctly that doubling the speed of a vessel can multiply the energy transferred in collision by a factor of four. However, they overlook the fact that the same relationship dictates that a large slow moving vessel can easily impact with the energy of a smaller fast moving vessel. A 23 ton sailboat moving at 5 MPH having its keel impact a manatee would impact with energy at about the same as that of a 1 ton boat moving at 24 MPH. A slow moving barge loaded with fuel oil can impact a manatee with a momentum that is orders of magnitude greater than that of any fast moving vessel.

If the slow speed zones were truly effective at reducing manatee mortality from the typical vessel that uses inland waters, then a stable or constant watercraft-related mortality percentage could be due to vessels that aren't affected by the slow speed zones. Perhaps, the FWC regulated the wrong vessels.

The authors refer to the registration history in a table, but for what purpose? Also, they do not mention the fact that the manatee population increase is by all accounts the cause of increase in manatee mortality. Their paper appears to be a conglomeration of beliefs and irrelevant data that does not support their thesis that slower boat speeds reduce risk to manatees.

Conclusion

The arguments presented by the authors are not compelling and may be by any reasonable standard considered specious. Suffice it to say that their lack of any empirical scientific data is somewhat underwhelming. When McGill's book, The Florida Manatee Conspiracy of Ignorance, was published in 2004, Scott Calleson and Kipp Frohlich were in the Bureau of Protected Species Management (BPSM) then headed by Dave Arnold. All three of these gentlemen epitomized the "ignorance" characteristic by their continuous application of Junk Science. Like Arnold's predecessor Pat Rose who had previously been the Chief of the BPSM in the Department of Natural Resources (DNR), they relied primarily on unsubstantiated claims and opinions to determine how best to protect the manatee. Today, more than 2 decades later the FWC management admits it isn't sure whether the slow speed zones are effective or not, but still they "believe."

Tom 11/15/07 References

Gerstein, E.R., 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.

Gerstein, E.R., Manatees, Bioacoustics, and Boats, American Scientist, April 2002, Vol. 90. Also, test data collected in Brevard county, var. locations, summer 2003.

McGill, Tom, "The Florida Manatee Conspiracy of Ignorance," RALCO Publishing, ISBN 0-9752945-0-4, Library of Congress Number 2004091848, 2004, available at Amazon.com McGill, T.D., "Critique of Several Studies of Boater Compliance with Manatee Slow Speed Zones," submitted to FWC on September 5, 2007.

McGill, T.D., "A Macro Level Approach to Evaluate the Effectiveness of Slow Speed Zones in Protecting the Florida Manatee from Collisions with Watercraft," submitted to FWC on June 19, 2007.

McGill, T.D., April 2006, Critique of "Preliminary Notice That Boat Speed Restrictions Reduce Death of Florida Manatees" by David W. Laist and Cameron Shaw," available from capttom@cfl.rr.com

Rommel, Sentiel A., Alexander M. Costidis, Thomas D. Pitchford, Jessica D. Lightsey, Richard H. Snyder, and Elsa M. Haubold., 2007. "Forensic methods for characterizing watercraft from watercraft-induced wounds on the Florida manatee (Trichechus manatus latirostris)." Marine Mammal Science, v.23 no.1, p.110-132.

Wood, James, "A Simple and Effective Method for Analyzing Propeller Marks on Manatee in Brevard County, Florida, August 2001," Go to: www.lumiatrex.com