NUMBER
IN THIS ISSUE:
- NEW
DUGONG POPULATION ESTIMATES FOR
(pp. 3-4)
- MANATEES
STILL ABUNDANT IN
EDITORIAL
As you
read this issue of Sirenews,
manatee conservation efforts in
Some
of the more important recommendations,
detailed in a 25-page DNR
document, are the following: mandatory boating safety courses for boat
operators; establishment of a statewide
maximum boat speed limit of 30 mph in or
near a marked channel or near a shoreline;
establishment of a maximum speed
limit of 20 mph in all inland waters
accessible to manatees in twelve key
counties, except in marked
channels where the limit
would be
30 mph; creation of
several new manatee
protection zones where
boat speeds would be still more tightly regulated;
designation of large manatee preserves from which boats and
swimmers would be excluded altogether; and further limitations on construction or expansion of powerboat slips.
Needless
to say, these proposals have
stirred up considerable
controversy in the state, especially on
the part of the boating industry.
In a number of raucous public meetings, boaters and
representatives of the
marine industries harshly criticized DNR's
recommendations as unacceptable to the
boating public. This allegation, however, was
dramatically blown out of the water by the recent release of a timely public
opinion survey of
In
other words, the
typical Florida boater is not
the irresponsible, reckless
driver of an overpowered speedboat, but
on the
contrary is deeply concerned about
safety, the public welfare, and the protection of natural resources, and
is willing to make sacrifices to promote all of these. In this respect (s)he is even out
ahead of his/her
elected officials, who
will hopefully see a mandate in
the results of this survey and find the political courage to take stronger
steps. We all owe the Save the
Manatee Club and its Executive Director,
Judith Delaney Vallee, a debt
of thanks for
supplying this badly
needed ammunition at a crucial moment in the battle.
Pat Rose,
Pam McVety,
and their staffs at DNR also deserve thanks for
the dedicated work that has
brought us to
this historic point. If the Governor and Cabinet adopt all of their recommendations
at this month's meeting, we will be a
large step closer to ensuring the future
of
CORRECTION
Randy Reeves has pointed out the error in
our last issue's headline. Among marine
mammals, not only
dugongs but also walruses form leks.
AWARD
Dr.
Edgardo Mondolfi, biologist, Venezuelan Ambassador to
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LOCAL NEWS
Dugong Numbers in
The results are very exciting. We estimate
that there are at least
10,000 dugongs (10,146 +_ s.e. 1478) in Shark Bay and a further 2000 (1964 +_ 363) in the Exmouth Bay-Ningaloo Reef area.
The distribution of animals in both
areas was unexpected. Although there were the expected large numbers of
animals along the eastern
shore of Dirk Hartog Island, there were also many dugongs
in water 11 to 19 m deep
extending right across
the central third of the Bay.
This distribution
pattern will be easier
to interpret when we obtain the satellite maps of thermal gradients in the
Bay at the time of the survey.
However, it
certainly suggests that further
investigations are needed into the
distribution of seagrasses and
dugong movements within the Bay.
The
dugongs were distributed along the western
side of Exmouth
Gulf as we expected, but we were
surprised to find that about half the
dugongs in the region were outside Exmouth Gulf in
the lagoon of the Ningaloo
Reef complex in exceptionally clear
water. Whether this is a seasonal
phenomenon is unknown, but the clear waters of Ningaloo
Reef certainly offer the best conditions I have seen to obtain good underwater
photographs of dugongs, as evidenced by the excellent photographs that have
been obtained by a local diver. - Helene Marsh
Update
on Dugong Numbers
for
Exmouth Bay-Ningaloo Reef 1964 +_ 363
Northern coast of the
Western
Torres Strait 12522 +_ 1644
TOTAL: 69266 +_ 4057
The
Dugongs in
Deep Water. - The importance of
water 10-20 m deep to dugongs is increasingly apparent. Rob
Coles and his group from the Queensland Department of Primary Industries
recently completed a survey of the seagrass beds in the northern
Great Barrier Reef region between Lookout Point, Barrow Point,
Lizard Island (30 km
offshore), the Howick
Islands and the mid-shelf reefs. The
survey was funded by the Great
Barrier Reef Marine Park Authority in response to my observations that
an estimated third of the dugongs in this area were sighted more
than 20
km offshore in an aerial survey
in November 1984 [see Sirenews No.
6]. Coles and his team found seagrass on more
than 95% of their dives and at depths to 28 m. Halophila was the only genus
of seagrass below 10 m. Dugong feeding trails
were seen down to 23 m in areas
with about 10%
cover of Halophila
spinulosa
and Halophila ovalis/decipiens. -
Helene Marsh
Manatee
Status in
Accounts from 10-20 years ago (see Charnock-Wilson, Oryx
9: 293-294, 1968 and Oryx 10: 236-238, 1970; Bengtson
& Magor, Jour. Mamm. 60:
230-232, 1979) reported that manatees were relatively common in
Belize in comparison
with other nations
of the Caribbean and Central America. However, aerial counts had not been attempted in
Numbers of manatees seen were comparable to or
greater than those seen in each of these areas during 1977, although all
the usual caveats about numbers obtained in manatee aerial surveys should be kept in mind. A total of
103 were noted in 5.4 hours of search time in May 1989. A unique circumstance was noted for the
inshore Southern Lagoon,
where some 55 manatees were counted (in turbid water) over a
relatively small area, apparently
drawn to an upwelling
freshwater spring. Nowhere else in the
greater Caribbean have comparable
numbers or densities
of manatees hitherto been
observed, except for the southern part
of Quintana Roo near the Bay of Chetumal bordering
Belize, as reported by Luz del Carmen Colmenero Rolon and her
colleagues in a recent agency report.
Manatee habitat in
This
population could serve
as a source
for natural recolonization in
nearby countries if
conditions elsewhere improve and at the same time do not deteriorate in
Belize. We hope that
as development proceeds such deterioration does
not occur. This can
be guarded against
by maintaining legal protection for manatees,
continuing to restrict gill-netting, creating manatee
reserves in areas like
Southern Lagoon, and continuing with manatee conservation education programs similar to the existing efforts of the Belize
Zoo. -
Tom O'Shea and Lex
We will offer this facility as a
resource to institutions wishing to
conduct research on manatees.
Grant monies will
be necessary for capital equipment required for projects. Lowry
Park Zoo will simply supply the work station.
We anticipate approving projects by early next
year for research to be conducted in late 1990 or early
1991. Interested parties should send their research proposals
for evaluation to: C. Lex Salisbury,
General Curator,
The facilities at
The caretaker on duty stated that there are four manatees impounded in the river at
present, all females. In earlier years
of the project, manatees were kept in the river by a fence at the river's mouth
and/or by being tethered by their tails with ropes. Now, however, he
said that there is a sandbar at
the river's mouth that keeps in
the manatees in lieu of a fence. He also said that the manatees prefer to stay near the
mouth and only come up into the
headwaters at night when it is
quieter. Therefore it seems unlikely
that the average visitor will ever
see one.
The visitors' register gave evidence of
only a few visitors
per week, and those mostly foreign. A two-page questionnaire solicited visitors' comments on the reserve and
its facilities. My main criticism was that the site, which lies two and a half miles from the nearest bus line, seems insufficiently accessible to the poorer inhabitants of the region, who are of course the ones
most in need of environmental education.
Greater human use of the area, on the other hand, would entail greater
expenditures for
facilities and park rangers and result in at
least some degree of harmful
impact.
On
the positive side,
the reserve is still in pristine condition and does not seem to be threatened by development
in the near future. But it must be doubted whether the
continued impoundment of manatees
in the river is justifiable, given that
they are
thereby removed from the already very
small breeding population in
Jamaican waters and
that there is minimal opportunity for
the public to
see them under
the present circumstances.
The
The
Sirenia Specialist Group stands ready to
assist these and other
such efforts throughout
the world with
whatever technical advice or
information we have at our disposal, and
we encourage the Jamaican
agencies involved to
develop their management plans without delay. The pressures of growing human populations throughout the
The World's Oldest Sirenian. - Also in September 1989,
I spent a week
in search of
additional fossil specimens
of Prorastomus
sirenoides,
the oldest and most
primitive known sirenian. This
beast was originally described in
1855 by
Sir Richard Owen on the basis of
a single skull from Freemans Hall, Jamaica; the
unique type specimen resides in the British Museum (Natural History).
No other specimens
have hitherto been reported. Although the
postcranial skeleton was
unknown, the extremely primitive features displayed by the skull had led to
the suspicion that Prorastomus
may still have been an amphibious animal
with functional hind legs. Hence
the collection of limb
bones was a high priority for fieldwork.
Together
with veteran fossil seacow collector
Frank Garcia (Museum of
Science and Industry, Tampa,
Florida) and Steve Donovan and Hal Dixon from the
Department of Geology, University of the
West Indies (Kingston), I visited the Freemans Hall area
in Trelawny Parish and searched for limestone nodules
of the sort that produced the original
specimen. Recent geological studies indicate that the most likely source beds of the
latter are not Middle Eocene
(as nearly all published works
state) but late Early
Eocene in age. This makes Prorastomus somewhat older than any other fossil sirenian yet named (50
million years in round numbers), and
supports the possibility that it may be an actual ancestor as
well as a structural ancestor of
other sirenians. Unfortunately, we
failed to turn up any bones in these strata.
We
also visited a spot
where a new species
of fossil crocodile was discovered in 1968, in northern Manchester Parish near the
charmingly named village of Dump.
Here we were more successful: in
beds of early Middle Eocene age, we recovered
skull fragments and
teeth indistinguishable from
those of Prorastomus, and with them several vertebrae and
ribs. We still did not get any hindlimb bones, so the question of amphibious vs. purely aquatic
locomotion is not definitively settled; but at
least we demonstrated the possibility of collecting more material of this
enigmatic creature and shedding
further light on the origins of the Sirenia. - DPD
Grant Awarded for Sirenian Bibliography. - The
Smithsonian Institution's
Atherton Seidell Endowment has awarded
a generous grant to aid in the indexing phase of the
sirenian bibliography project during
1989-90. This will enable me to spend a large part of my sabbatical leave this academic year on indexing the
most essential of those works in the database that have not already been
indexed, and on
entering the index into the
computer. Computerization of
the main bibliographic entries,
A-Z, was completed this past
summer. Once the high-priority indexing and
computerization of the index are finished, it will be possible to produce
camera-ready copy for publication of a first edition. The Smithsonian Press has expressed interest in
publishing the work in its new
occasional series Smithsonian Research Monographs; it will most likely comprise two sizable
volumes.
I wish to express my thanks and those of
the entire sirenian research and conservation community to the Seidell Endowment, and to Dr.
Clayton E. Ray for his
indispensable help in
obtaining this grant and his enthusiastic support of this project
over many years. - DPD
REVIEW
What is Statistics?
Videotape
produced by the Chedd-Angier Production
Co. for the
Consortium on Mathematics
and its Applications (COMAP),
1989. (Available from
the American Statistical
Association,
This
short video (about
15 minutes) provides
a quick overview of the kinds of problems to which
statistical analysis can be applied. The
dozen or so examples are taken from medicine, baseball, meteorology, industrial
quality control, political polls, gambling, social science
research, and other fields. These are excerpted from a much more elaborate,
26-part series from the same producer entitled Against All Odds: Inside
Statistics, which presents
the elementary statistical
concepts underlying the applications. These videos
are well produced
and would be suitable for high school students or the
general public.
My
reason for reviewing them in these pages is that
the short tape includes a
35-second segment on Florida
manatees (I have not
been able to view the longer
segment in the 26-part series of which this is presumably an
abridgement). This short segment shows footage of
manatees and a power plant, and states that the significant correlation of
manatee deaths with number of boat registrations
in
What
strikes me as impressive about this is the following: the manatee death/boat registration correlation
is evidently so clear and striking that
it was one of only about a dozen examples chosen by professional statisticians
to illustrate the most basic concepts in a 15-minute introduction to their own
field. However, I have never
seen this particular
correlation emphasized or illustrated
in any of the education materials created to inform the public about manatee
protection. Sure, we talk
incessantly about boat kills;
but a simple, compelling graph of
deaths against boat registrations (an index of human population growth),
or better yet, against population growth
itself, would have an impact
at least as valuable to our sales
pitch as it is to the
statisticians'.
I understand from DNR that they are now
making these points in their presentations to public hearings. My advice is
that these points cannot be made
too often or too vividly. Not just unsafe
operation of boats but
sheer numbers of
boats, and ultimately numbers of
people, are the heart of the crisis. To
my great surprise, however, I was recently told by two DNR officials that these
facts are now so well known by the Florida public that they are
taken for granted
(and hence not
necessary to emphasize?). I hope
this is true, but given the American public's widespread lack
of awareness of the dimensions and
effects of overpopulation, I am inclined to doubt it. Even if the facts
are accepted, their political implications are not; and if
growth management legislation is
going to be made to stick, a lot of
people, and especially elected officials, still have to be beaten over the head
with the obvious. - DPD
ABSTRACTS
Applications of the
Geographic Information System
to Manatees (Trichechus manatus)
in
Zoogeography of Marine Mammals in
RECENT LITERATURE
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1987. Man and manatee: planning for the future.
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(
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P., and W.J. Freeland. 1989. Seasonal
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dugongs in the western
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D.P. 1989. Kelp evolution: a comment.
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Estes, J.A.,
and P.D. Steinberg. 1989.
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