Title: Sirenews
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00099157/00019
 Material Information
Title: Sirenews newsletter of the IUCNSSC Sirenia Specialist Group
Alternate Title: Siren news
Physical Description: v. : ; 29 cm.
Language: English
Creator: International Union for Conservation of Nature and Natural Resources -- Sirenia Specialist Group
International Union for Conservation of Nature and Natural Resources -- Sirenia Specialist Group
Publisher: IUCN/SSC Sirenia Specialist Group
Place of Publication: Washington D.C
Washington D.C
Publication Date: April 1993
Frequency: two no. a year[apr. 1984-]
Subject: Sirenia -- Periodicals   ( lcsh )
Marine mammals -- Periodicals   ( lcsh )
Genre: periodical   ( marcgt )
Bibliography: Includes bibliographical references.
Additional Physical Form: Also issued via the World Wide Web.
Dates or Sequential Designation: No. 1 (Apr. 1984)-
Issuing Body: Supported 1984-Apr. 1992 by the Species Survival Commission of IUCN, the U.S. Fish and Wildlife Service, and the U.S. Marine Mammal Commission; Oct. 1992 by the U.S. Marine Mammal Commission & U.S. Fish and Wildlife Service; Apr. 1993-Oct. 1994 by the U.S. Marine Mammal Commission; <Oct. 1995>- by the U.S. Marine Mammal Commission and Sea World, Inc.
General Note: Title from caption.
General Note: Latest issue consulted: No. 48 (Oct. 2007).
 Record Information
Bibliographic ID: UF00099157
Volume ID: VID00019
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 35841617
lccn - 2009208704
issn - 1017-3439


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Full Text
Sirenews (ISSN 1017-3439) appears twice a year

Sirenews (ISSN 1017-3439) appears twice a year
in April and October and is edited by Daryl P. Domning,
Department of Anatomy, Howard University, Washington, D.C. 20059 USA
(fax: 202-265-7055). It is supported by the U.S. Marine Mammal Commission.






A Sirenia Workshop will be held at the Sixth International Theriological Congress in
Sydney, Australia, in early July 1993. The date of the workshop is not confirmed but will
probably be Wednesday, 7 July. The following titles of spoken papers are provisional, and the
program itself is still subject to modification. It will, however, occupy one full afternoon
(1330-1730) and be chaired by Dr. John E. Reynolds, III. Each paper will be allotted 20
minutes. The workshop theme is "The interactions between seacows and their food." Attendees
are also invited to submit posters, and there will be a poster session scheduled for the morning
of 7 July. The following is the tentative program for the workshop.

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Sirenia Workshop ITC 6
The Interactions Between Seacows and Their Food

Spoken Papers:

Janet Lanyon: "Why dugongs are fussy eaters: a nutritional basis for
food selection in dugongs"

Cathy Beck: "Food habits of the Florida manatee in estuarine

Lynn Lefebvre, Jane Provancha, Jud Kenworthy, & Cathy
Langtimm: "Assessing manatee grazing effects on seagrasses"

Jane Provancha: "Manatees and seagrasses in the northern
Banana River, Florida, USA"

Hans de Iongh et al.: "Herbivore-plant interactions between
dugongs and seagrass communities in Malaku Province, Indonesia"

Brad Weigle: "Manatee habitat use in Florida: the role of telemetry
and Geographic Information Systems"

Helene Marsh: "Dugongs and seagrasses in Australia: the big picture"

Tony Preen: "The effect of the loss of 1000 km2 of seagrass on
dugongs in Hervey Bay, southern Queensland"

Nina Morissette: "Are dugong habitats safe from anthropogenic
impacts in the Great Barrier Reef Marine Park?"

Open discussion led by Galen Rathbun: "Seacows and
seagrasses: priorities for unstudied populations and recommendations to the
Sirenia Specialist Group"

Several people have expressed interest in a possible field trip to see dugongs in
Moreton Bay near Brisbane after the conference. The best way to do this would be to charter
an aircraft. The cost would probably be about AUS$100 per person (approximately US$70 per
person) for a two-hour flight. The tides are possible, but not ideal, immediately after the

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workshop, so it may be possible to organize a flight for the afternoon of Monday, 12 July.
Alternatively, the tides are better on Tuesday, 20 July, but that would certainly involve people
staying around for quite a while after the conference. Anyway, those of you who are interested
in participating in such a flight, please contact Tony Preen at the Environmental Studies Unit,
James Cook University, Townsville, QLD 4811, Australia (fax no. +61-77-815581).
We are looking forward to seeing as many of you as possible at the conference in
Sydney. Helene Marsh


A Regional Workshop on the Status and Management of Manatees in the Wider
Caribbean has been tentatively scheduled for September or October of 1993 in Kingston,
Jamaica. It will be sponsored by the Caribbean Environment Programme of UNEP. For
further information contact the Natural Resources Conservation Authority (NRCA), 53 1/2
Molynes Road, Kingston 10, Jamaica; telephone (1-809) 923-5155; fax (1-809) 923-5070.


Save the Manatee Club is interested in receiving proposals for research, the results of
which can be used to effect and affect management policy for the recovery of manatee species
in the wild.
Effective immediately, the Club will consider proposals for research funding twice a
year. In 1993, proposals will be considered in March and July. In 1994 and thereafter, the first
round of proposals will be considered no later than November of the previous year. For
example, proposals for the first half of 1994 must be received by November 30, 1993. In June
of 1994 we will review the second round of proposals for that fiscal year. Requirements for
proposals are as follows:

1. Please submit ten (10) copies of your proposal to Judith Vallee, Executive Director,
Save the Manatee Club, 500 N. Maitland Ave., Maitland, Florida 32751 USA.

2. Please make sure your proposal addresses the following:
a. Clearly and concisely state the purpose and need of the proposed research.
b. State the methodology that will be used.
c. State the approximate time frame of the research.
d. State the names of the investigators and cooperating agents and provide a
brief statement of their qualifications.

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e. If only partial funding is requested, please include budget for cooperating

3. State how you expect your proposed research to influence management policies.

4. Save the Manatee Club requires quarterly updates and an annual report to be
submitted with request for payment.

5. All proposals should include a literature review and citations in addition to
answering the above criteria.

Proposals are reviewed for merit by the Club's Scientific Advisory Council and its
Executive Committee. Please allow two (2) months for review.



Loss of Seagrass and Loss of
Dugongs. Until recently, Hervey Bay,
in southeast Queensland, supported the
second-largest seagrass meadow and dugong
"population" in eastern Australia. A large
flood in the Mary River in February 1992
was followed three weeks later by the
passage of a downgraded cyclone and a
second flood. These events were coincident
with what now appears to be the death of
virtually all of a 1000 km2 seagrass
meadow that stretched from the intertidal
zone to a depth of 20 m in southwest Hervey
Bay. During a 1988 survey, seagrass cover
at the 53 of 97 sample sites (55%) in the
southwest of the Bay that contained
seagrass averaged 39.5%, with a maximum
of 100%. In the same area in January
1993, 11 of 79 sites (14%) contained
seagrass, but often only isolated plants. The
average ground cover was just 1.5%, and the

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maximum was only 7%. Sixty-six of the sites
sampled in 1988 were resampled in 1993. At
those sites, average seagrass cover changed
from 39.0% (range = 0.1-100%) in 1988 to
0.13% (range = 0-5%) in 1993. At eight
sites where seagrass was recorded in 1988,
but not in 1993, the remains of dead seagrass
rhizomes were found during the 1993 survey.
During the second half of 1992,
unprecedented numbers of dead dugongs
were recorded from Hervey Bay and areas to
the north and south. Autopsies revealed that
most of the animals were emaciated, and
starvation was likely to be the ultimate cause
of death. Some animals had unusual food
items in their stomachs, including algae,
decomposing fiber and sand. The number of
dugongs that died in Moreton Bay (260 km
south of Hervey Bay) and in New South
Wales (NSW), south of the dugongs' normal
range, suggested there had been a mass
exodus of dugongs from Hervey Bay. While
only eight dugongs had been recorded in
NSW in more than 30 years prior to 1992, at
least 17 dugongs were reported from that
state in the second half of 1992.
The population of dugongs in
southern Hervey Bay in 1988 was estimated
to be 1466 (+_326). In November 1992,
the same area had an estimated population of
50 (+_33). At the same time, the population
in the Great Sandy Strait (GSS),
immediately south of Hervey Bay, changed
from 291 (+_135) to 656 (+_272), confirming
local fishermen's suggestion that many of
the displaced dugongs moved into this area.
However, the estimated total population of
the Hervey Bay region (including GSS)
changed from 1971 (+_359) in 1988 to 787
(+_277) in 1992, suggesting that a large

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number of dugongs died or left the area.
Seventy-four dead dugongs can be
accounted for.
The February 1992 flood of the Mary
River was the third largest this century. In
combination with the Burrum River, this
flood presumably put a huge plume of turbid
water into Hervey Bay. This plume would
have shaded the light-demanding seagrasses,
especially in the deeper areas where most of
the seagrass occurred. As a result of the
reduced photosynthesis, the seagrasses would
have starved. Three weeks after the flood,
ex-cyclone "Fran" passed over Hervey Bay,
physically excavating large amounts of
seagrass. Wave action would have
resuspended fine sediments, and the flood
produced by the cyclone presumably put an
additional load of turbid water into the Bay.
The combination of these events is likely to
have been responsible for the massive loss
of seagrass over such a wide area.
Although the initial flood was big, it
was far from a record height (21.4 m cf.
25.45 m at Gympie, and 9.5 m cf. 12.27 m
at Maryborough). Oral history suggests that
no flood in the previous 100 years has had
such an impact on the seagrasses, as the
dugongs have not, in the past 90 years,
disappeared as they now have. There are
several possible explanations for the
destructiveness of the 1992 flood. These
include a relatively greater sediment load due
to greater erosion in the rivers' catchments,
the influence of the tropical depression,
and the impact of pollutants flushed from
the catchments.
There is no doubt that the catchments
of the Mary River and the Burrum and
associated rivers had less forest cover than

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during previous floods, especially during
the last decade of last century, when
three record floods occurred. There is also
no disputing the considerable erosion
associated with the 1992 flood on the Mary
River. However, I have no data on the
sediment loads during different floods to
establish clearly a relationship between
land practices and seagrass mortality.
Cyclones have been implicated in the
loss of seagrasses in the southwestern Gulf of
Carpentaria. However, ex-cyclone "Fran"
was a weak system, and maximum
10-minute-average wind speed was only 40
kt. Substantial amounts of seagrass were
washed onto Hervey Bay beaches, but the
extent to which these seagrasses had been
weakened or already died as a result of the
preceding flood is unclear.
Local fishermen are convinced that
pollution flushed out by the flood was
responsible for the die-off of seagrass and
intertidal life. Experiments have shown that
herbicides at concentrations of 100 ppb
can result in substantial seagrass
mortality, although most experts feel that
the dilution during a large flood would be
too great for any impact to occur.
There has been a suggestion that
prawn/shrimp trawler activity, which was
very high in southwest Hervey Bay at the
time of the flood, may have been involved in
the seagrass decline. In the absence of data
on the effects of trawl gear on seagrasses,
especially stressed seagrasses, this suggestion
cannot be discounted.
This loss of seagrass from Hervey
Bay is very significant, representing
approximately 25% of the known
seagrass area between the tip of Cape York

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Peninsula and Hervey Bay, a distance of
some 2300 km. According to local
professional fishermen, the loss of
seagrass has been reflected in
dramatically reduced catches of several
important species of fish.
Ten months after the perturbations
that killed the seagrass, no germination or
recovery could be detected in the areas
previously rich in seagrass. Experience in
other locations suggests that recovery could
take up to a decade. Assuming that seagrass
will not be limiting, recovery of the dugong
population will take a minimum of 30-60
years (depending on assumptions).
The events of 1992 have important
implications for the conservation of dugongs.
The fact that the second most important
dugong area along the east coast of Australia
can be so dramatically altered in such a short
time is alarming. Large dugong populations
associated with large areas of deep-water
seagrasses (like Hervey Bay) may not be as
stable as previously assumed. It is important
that the recovery of the seagrasses and
dugongs in Hervey Bay be monitored.
Information on these recoveries will
provide important guidelines for the
management of seagrass habitats elsewhere.
- Tony Preen


Save the Manatee Club and Florida
Audubon Reach Agreement. On March
18, 1993, the legal dispute between Save the
Manatee Club (SMC) and the Florida
Audubon Society (FAS) was ended by the
signing of an agreement making the two
organizations fully independent and pledging

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them to work together for the protection of
manatees. The accord, described by the press
as "a sort of no-contest divorce agreement",
was signed at Wekiwa Springs State Park in
central Florida, and is expected to be
approved by Florida Governor Lawton Chiles.
The dispute had arisen when SMC
sought to separate its affairs from those of
FAS, under whose tax exemption SMC had
originally been organized (see Sirenews Nos.
17 and 18). In March 1992, FAS seized
SMC's assets and removed its Executive
Director. SMC sued successfully and
obtained a court injunction restoring its
autonomy. The new agreement affirms
SMC's exclusive rights to its trademarks,
logos, and other assets; it will now have its
own tax-exempt corporate status.
Members of both organizations will
form a new effort called Toward Education
and Advocacy for the Manatee (TEAM).
SMC will spend $10,000 annually for three
years on the program and another $10,000 a
year to help FAS lobby the state government
for manatee protection. (Source: Orlando

Save the Manatee Club Offers
Reward. Save the Manatee Club is offering
a $1500 reward for any information leading
to the arrest and conviction of the person
or persons who allegedly roped a manatee
and forced the animal to pull a boatload of
people around the Homosassa River near
Homosassa Springs, Florida, recently. The
U.S. government can also offer a reward
of up to $2500 for violations committed
under the Marine Mammal Protection Act of
1972 and the Endangered Species Act of

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As reported in the Feb. 26, 1993,
edition of the St. Petersburg Times, the
incident took place at Blue Waters, an area of
the Homosassa River just outside of
Homosassa Springs State Wildlife Park. A
visitor at the park reported to authorities that
a pontoon boat was being pulled around the
area by a manatee that had been tied to
the boat. According to the witness, the
manatee was able to get loose, but the boat
operator went after it and the boat hit the
manatee. Help was solicited from park
volunteers and other boaters in the area, but
no one was able to get identification
numbers from the craft.
Law enforcement officials report that
the incident is a federal misdemeanor
punishable by a fine of up to $100,000 and/
or one year in prison. Under Florida state
law, the incident is considered a
misdemeanor and is punishable by a fine of
up to $1000 and/or one year in prison.
This incident of manatee harassment
is one of several that have been reported in
Citrus County lately. Recently, it was
reported that divers caused a separation of a
mother manatee and her calf in the spring
waters of Kings Bay in Crystal River, and
also that a group of people were climbing
on manatees that were mating near Three
Sisters Spring. A suit filed in October 1992
against the U.S. Fish & Wildlife Service
by a coalition of environmental groups
claims that the Service is not properly
managing national wildlife refuge lands and
is allowing incompatible use of those lands.
The lawsuit names 11 different national
refuges, including the Crystal River
National Wildlife Refuge because of
conflicting recreational activities in a refuge.

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Anyone with information pertaining to
the Homosassa River violation can call the
Citrus County Florida Marine Patrol District
Office at (904) 382-5058 or, if they live
outside Citrus County, they can call the
Florida Marine Patrol Manatee Hotline
number at 1-800-DIAL-FMP. Callers should
refer to Complaint Number C93-03-0142 and
may remain anonymous if they choose.
For a free brochure on manatee dos
and don't or for information about
manatees, call Save the Manatee Club at 1-
800-432-JOIN, or write: SMC, 500 N.
Maitland Ave., Maitland, FL 32751.


New Manatee Contact in West
Africa. Dr. Michael Jones, currently a
biology lecturer at Gambia College, has a
long-standing interest in sirenians and joins
the vanishingly small contingent of such folks
presently in West Africa. He reports that "it
appears that the manatee may be more
numerous in the River Gambia than the
limited amount of literature suggests,
although it has obviously declined in
numbers." We hope he will have the
opportunity to gather more data on this, the
least-studied species of living sirenian. His
addresses are: 13 Princess Street,
Wrexham, Clwyd LL13 7UR, Great Britain;
and c/o British High Commission, P.O. Box
507, Banjul, The Gambia; fax 96134.


New Dugong Project at Salim Ali
Centre. This center was established nearly
a year ago in memory of Dr. Salim Ali to

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conduct research in areas related to nature
conservation. It is an autonomous center of
the Ministry of Environment & Forests,
Government of India. One of our major
initiatives is on ecological and population
studies on marine mammals of the Indian
coast. We are starting off with a project
on the dugong. The Indian population of this
species has dropped drastically in the
last three decades. It has almost
disappeared off the Saurashtra coast, and is
very threatened in its stronghold, the Gulf of
Mannar. Even in the Andaman and Nicobar
Islands the population has been going
down over the years. In contrast to the
eastern Indian Ocean, no ecological or
population studies of the species have been
carried out in the western end of the Indian
The major objectives of our project
are to (1) assess the population's distribution,
abundance and status off the Indian coast; (2)
assess its major habitat requirements; (3)
identify major threats; and (4) assess the
distribution and status of potential habitat.
We hope to conduct aerial and ground
surveys for population and habitat
assessment. We would conduct intensive
ecological studies at one or two sites (Gulf
of Mannar and Andaman and Nicobar
Islands) to assess habitat requirements. We
plan to use satellite telemetry to track long-
distance movement of 1-3 groups, if possible.
We are, therefore, very keen to
receive copies of relevant publications
and reports, especially those dealing with
methodology of studying marine mammals.
We are also keen to hear about the feasibility
and costs of radiotelemetry. We are
presently looking for funds for the project,

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and would appreciate being informed of
potential funding sources. Ajith
Kumar (Principal Scientist, Salim Ali
Centre for Ornithology and Natural
History, Kalampalayam P.O., Coimbatore-
641010, India; fax/phone 0422-32273)


Dugongs in Thailand. Dugongs are
known as an endangered species in Thailand.
Five years ago, no one but fishermen knew
where they lived in the surrounding areas.
Dugongs were accidentally caught in
fishermen's nets and drowned.
Unfortunately, illegal techniques of fishing
such as push-netting and dynamite have
been destroying the seagrass beds which
are the dugong's main source of food.
Between 1980 and 1992, the Royal
Thai Fisheries Department nursed four
dugongs, all of which were accidentally
caught by local fishermen. The first dugong,
a 1.2-m calf, was nursed in a 5 x 4 m
concrete tank for one year and died. The
second dugong was caught by gillnet in
Trung Province and died after being reared
for only four months. The third calf was
caught in Phuket Province; it too died
after being reared for six months. The last
dugong was caught in Satun Province. It was
reared for a few months before being
released into the seagrass bed at Libong
During the rearing period, the
dugongs' behavior and health had been
monitored by researchers at the Phuket
Marine Biological Centre. Some dugongs
tended to be weak, lose their balance
and drown. Others were killed by infection

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from bacteria and parasites.
The Royal Thai Forestry Department
observed dugongs in the Andaman Sea in
1991. An aerial survey was conducted using
a helicopter in Had Chao Mai National Park
and Libong Non-Hunting Area. This area is
reported by marine biologists to be the richest
seagrass bed in Thailand, and dugongs were
frequently seen there by local fishermen.
After three aerial surveys, several dugongs
were located in this area (see Sirenews No.
17, and the report below).
Since this survey, the plight of
dugongs in Thailand has been presented in
newspapers, magazines and television to
increase public awareness to protect dugongs.
Non-government organizations such
as Wild Life Thailand and the Yard Phon
organization have become interested in
dugongs. These organizations try to
encourage the local fishermen to protect
seagrass beds and dugongs. Fishing styles are
difficult to change. However, after an
intensive campaign in the villages, illegal
fishing has been reduced. A group of
leaders from the village accompanied the
scientists on the last aerial survey. This led
to a change in the attitude of the fishermen
towards dugongs.
Today people at Libong Island try to
protect their seagrass beds and dugongs.
However, there is still illegal fishing in
seagrass beds in other areas such as in the
Gulf of Thailand (Rayong, Chanthaburi and
Trat provinces).
Sudara and Nateekanjanalarp (1992)
reported that there were few dugongs seen or
accidentally caught by fishermen. Sudara et
al. (1991) reported several species of seagrass
such as Enhalus acoroides, Halodule

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pinifolia, and Halophila ovalis in the Gulf of
Thailand. However, there were no scientific
data on distribution of dugongs in this area.
The campaign was not only successful
in stimulating public awareness of seagrass
beds and dugongs, but also initiated
cooperation between several
organizations (both government and non-
government). However, this issue seems to
be regarded as less important in Thailand
than others like mangroves and coral reefs
because there is not enough information,
especially scientific data, to support the
campaign. More research is needed. -
Piyaporn Manthachitra

Update on Dugong Aerial Surveys
in Thailand. From 29 March to 3 April
1992, the third aerial survey of the Dugongs
and Seagrasses Distribution Study Project in
Haad Chao Mai National Park was carried
out over the middle southwest area of
Thailand's Andaman Sea coast by a
National Parks Division group from the
Royal Thai Forestry Department,
consisting of Suwan Pitaksintom, Wijarn
Witayasak, Rattana Rukanawarakul,
Vissanu Rukvisaka, and Sean O'Sullivan.
Sixty-one dugongs (including 8 pairs of
cows and calves) were observed on a
seagrass bed off the shores of the national
park and Talibong Island. This is the highest
number counted since surveys were begun
in December 1991 (see Sirenews No. 17).
These sightings were the biggest
nature-conservation news in Thailand at the
time, and were very helpful in motivating
conservation campaigns. Not long ago, most
Thais knew dugongs (known locally as Pa-
yoon) only as mythical animals or mermaids

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(Ngiork), which are mentioned in the well-
known mythological poem Pra Apai Manee.
Now the popular understanding of dugongs
has been much changed due to these new
discoveries, though very few people can see
dugongs swimming freely in their natural
In December 1992, the Royal Forestry
Department, a group of Thai conservationists
from 11 private companies called the
Think Earth Group, and several
nongovernmental organizations organized
the Conserve Dugong Week in Trang
Province. This movement persuades people
to view dugongs as an extremely
endangered species which normally should
be strictly preserved and not even be touched.
Several questions remain concerning
dugong conservation and management. For
example, very few data have been collected
regarding the herd we observed, what
seagrass species they eat, the exact number
of dugongs in the area, the extent of their
daily or seasonal migrations, and so on.
Sometimes dugongs have been accidentally
caught in fishing nets, making them rarer in
the area.
In order to gain more information
about dugongs and their occurrence in the
area, the National Parks Division has recently
tried to radiotag them and thereby collect
data on individuals. However, the Thai
Fisheries Department has unfortunately
objected to the attempt and declared that
radiotagging of dugongs would be useless.
I would much appreciate it if anyone
with experience in dugong biotelemetry
techniques and observations on dugongs in
small groups would send me his or her
comments. I am a scientist in the National

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Parks Division and currently the acting leader
of the Dugong Survey Project in Thailand,
succeeding Mr. Sean O'Sullivan who has
returned to the United States. Suwan
Pitaksintorn (National Parks Division,
Royal Forestry Department, Paholyothin
Road, Chatuchak, Bangkok 10900, Thailand;
fax 579-2791)


Project Mermaid. During the three
months of summer 1992, five biology
students from the University of Newcastle
Upon Tyne conducted a feasibility study
for the setting up of a manatee research
station in northeastern Venezuela. The study
area was located in the State of Sucre, in a
mangrove-lined river, Cano La Brea, a
tributary of the Rio San Juan, north of the
Orinoco delta.
Project Mermaid was invited to
conduct the research by Sr. Claus Muller, the
founder of the Vuella Larga Foundation, a
non-governmental organization that assists
conservation projects throughout the region.
Sr. Muller has been involved in manatee
research in the past, and is the local expert on
the species.
The expedition team lived on a
floating platform on the river and completed
three weeks of surveying from a dugout
canoe. The manatee research involved
observing and recording evidence of
manatee activity and actual sightings along
the length of Cano La Brea. Firm evidence
of the presence of manatees was
obtained. A survey of other vertebrate
species in the area was also carried out. A
full report is being prepared, and funds are

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being sought for continuation of the project.
- Lucy Ward (c/o Dr. P. J. Garson, AES,
Ridley Bldg., Univ. of Newcastle Upon
Tyne, NE2 1JX, England; fax 091-


Age Determination and Population
Biology of the Florida Manatee, Trichechus
manatus latirostris (Miriam Marmontel). -
Florida manatees (Trichechus manatus
latirostris) are at risk due to modern stresses
on the population, primarily from boat
traffic and habitat alteration. These stresses
have population consequences which have
been little understood. Life history and
population studies have been hampered by
the lack of a method of age estimation.
Skeletal material of 16 known-age,
minimum known-age, or tetracycline-
marked Florida manatees (Trichechus
manatus latirostris) was prepared using
modifications of histological techniques
employed in age-determination studies of
dolphins. Results consistent with known age,
minimum known age or tetracycline-labeling
were obtained only from the dome region of
the periotic bone. Age-specific aspects of
mortality and reproduction were evaluated for
1,212 manatee specimens collected between
1976 and 1991. Approximately 59 layers
were found in the periotic dome of one
manatee of unknown age, and several had
growth-layer-group counts ranging from 21-
39. Sexual maturation can occur between 3
and 4 years of age, with first calving as early
as age class 4. At any one time 33% of the

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mature females were pregnant, indicating an
average calving period of 3.0 years.
Fecundity remained relatively
unchanged (0.24 female offspring/adult
female/year) from age of first parturition
throughout life. Half the carcasses belonged
to age classes 0, 1 and 2, and average age
was low (5.7 years). Survival rate was low
among the very young, increased up to
age class 4, and remained constant (89.9%
+_ 0.013) from age class 4 to at least 25.
The manatee survivorship curve is
consistent with the type expected in a long-
lived mammal, but lacks a plateau through
middle age. The steeper gradient is attributed
to exacerbated levels of adult mortality represented by the constant threat of collision with
watercraft. Death from intense cold affected mostly juveniles, but the effect of boat strikes was
constant across age classes. Life table analyses revealed a finite rate of increase r = 0.5%,
indicating virtually zero population growth. Computer simulation (VORTEX51) projected a
97.3% chance of persistence of the population for 1,000 years. The current situation allows no
margin of error. If increasing numbers of boats result in more deaths, the manatee population
will tend toward extinction. Only cultural change will prevent this outcome. [Abstract of a
doctoral thesis in Wildlife and Range Sciences submitted to the University of Florida in April
1993 and supervised by Stephen R. Humphrey and Thomas J. O'Shea.]


Anonymous. 1988. [The manatee Trichechus manatus.] Priroda (Sofia) 1988(2): 110.
[In Bulgarian.]

Colares, E.P., I.G. Colares, and A. Domingos do Amaral. 1992. Blood parameters of
the Amazonian manatee (Trichechus inunguis): dietary variation. Comp. Biochem.
Physiol. A. Comp. Physiol. 103(2): 413-415.

Fox, A. 1989. Crystal River's gentle giants. Aquatics 11(2): 16, 18.

Francis-Floyd, R., J.R. White, C.L. Chen, P.T. Cardeilhac, and C.E. Cichra. 1991.
Serum progesterone and estradiol concentrations in captive manatees, Trichechus
manatus. Jour. Aquat. Anim. Health 3(1): 70-73.

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Goodwin, R., and P. Thompson. 1991. Florida takes steps to make its waterways safer
for manatees and boaters. Florida Nat. 64(3): 11-12.

Hughes, C.D. 1993. The manatee: rescue at sea. Sky Magazine (Delta Air Lines) 22(3):

Lal Mohan, R.S. 1991. Research needs for the better management of dolphins and
dugongs of Indian coast. Cent. Mar. Fish. Res. Inst. Bull. 44(3): 662-667.

Lauckner, G. 1985. Diseases of Mammalia: Sirenia. IN: 0. Kinne (ed.), Diseases of
marine animals. Vol. 4, Part 2. Introduction, Reptilia, Aves, Mammalia. Hamburg,
Biol. Anstalt Helgoland: 795-803.
Lee, D.S., and M.C. Socci. 1989. Potential effects of oil spills on seabirds and selected
other oceanic vertebrates off the North Carolina coast. Occas. Pap. North Carolina
Biol. Surv. 1989-1: 1-64.

Morales V., B., and L.D. Olivera G. 1992. De sirenas a manaties. Chetumal
(Mexico), Centro de Investigaciones de Quintana Roo (Cuaderno de Divulgacion 4): 1-
30. [In Spanish.]

Petocz, R.G. 1989. Conservation and development in Irian Jaya. A strategy for
rational resource utilization. Leiden, E.J. Brill: xxii + 218.

Pledge, N. 1992. First record of fossil sirenians in southern Australia. Fossil Collect. No.
37: 6.

Popov, V., and A. Supin. 1990. Electrophysiological studies of hearing in some cetaceans
and a manatee. NATO Adv. Sci. Inst. Ser., Ser. A, Life Sci. 196: 405-415.

Prieur, A.; and C. Guerin. 1991. Decouverte d'un site prehistorique d'abbatage de
dugongs a' Umm al-Qaiwain (Emirates Arabes Unis). Arabian Archaeol. Epigr. 2(2): 72-
83. [In French; English summ.]

Rathbun, G.B. 1993. [Review of] Manatees and Dugongs [by] J.E. Reynolds, III, and D.
K. Odell. Mar. Mamm. Sci. 9(1): 114-115.

Reeves, R.R., B.S. Stewart, and S. Leatherwood. 1992. The Sierra Club handbook of
seals and sirenians. San Francisco, Sierra Club Books: xvi + 359. [ISBN 0-87156-656-
7. US$18.00. Sirenians, pp. 259-293.]

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Sakae, T. 1992. Comparison of mineralogical characteristics of tooth enamels of
Desmostylus from California, USA, and Minowa, Japan. Jour. Fossil Research 25(2):
37-42. [In Japanese.]

Thewissen, J.G.M. 1993. Eocene marine mammals from the Himalayan foothills.
Research & Exploration (National Geographic Society) 9(1): 125-127.

Venkateswarlu, T. 1990. Marine mammals of the Indian seas. Environ. Ecol. (Kalyani) 8
(3): 1050-1052.

West, J.A., J.G. Sivak, C.J. Murphy, and K.M. Kovacs. 1991. A comparative study of
the anatomy of the iris and ciliary body in aquatic mammals. Canad. Jour. Zool. 69(10):
2594-2607. [French summ.; includes data on T. manatus.]

Wolf, M. 1993. Meet the manatee. USAir Magazine 15(3): 80, 82-4, 86-87.


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Governments of all countries have been requested to prepare national population reports for the
U.N. International Conference on Population and Development, Cairo, Egypt, 5-24 September

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Sirenian Bibliography .... The Bibliography and Index of the Sirenia and Desmostylia has
been formally submitted for publication in Smithsonian Contributions to Paleobiology. ....

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