Journal of Global Resources

Volume 2January 2016
Page 26-29
ISSN: 2395-3160 (Print), 2455-2445 (Online)

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IMPORTANCE OF DUGONG PROFILE INUNDERSTANDING ITS CONSERVATIONALONGTANZANIA COAST
1Adelaide E. Sallema1 and Omar A. Amir2
National Museum of Tanzania, Dar es Salaam, Tanzania
2
Ministry of Livestock and Fisheries, Zanzibar
Email: adelaide5mon@yahoo.co.uk

Abstract: A study to estimate abundance, distribution and evaluate magnitude of dugong threats
and status in selected sites based on surveys was conducted between 2008 and 2009 duringsouth-east and north-east monsoon periods respectively. Conservation initiatives were also
assessed by involving local communities in monitoring activities. Findings show that 10 sightings oflive 9dugongsverified and localized in areas of Kilwa, Somanga, Rufiji and Mafia. Threats including
entanglement in fishing gear, dynamite fishing, trawling, habitat destruction and pollution persist.
The study recommends monitoring of dugongs and their habitats and future impact assessments
for inshore marine and estuarine developments involving local communities for conservation ofdugongs in Tanzania.
Keywords: Dugong, Monsoon, Conservation, Habitat Destruction, Conservation
Introduction
Despite their relatively extensive range (IUCN 2000) in 43 countries bordering the tropical, subtropical Indian and Western Pacific Oceans (IUCN, 1990)most dugong populations are small andnear to extinction due to increasing anthropogenic pressures (IUCN 2000).The sea grasses arefound in sheltered coastal waters less than 10 m in depth where dugongs are affected byanthropogenic impacts which may drive them away from food sources due to deterioration inquality of sea grasses. Dugongs were hunted for meat when they were abundant in 1950s.
Estimation of population size and distribution range of dugongs has sharply declined in 1990s(Chandeet al., 1994; Marsh et al., 2001), due to entanglement in fishing gear, excessive hunting,
dynamite fishing, prawn trawling, habitat destruction and pollution (Cockcroft and Krohn 1994).
Mortality rate from incidental killings persists and 1 dugong after 2 years can be found caught ingillnet in 2000s.The earliest record onpopulation status, occurrence and threats of dugongs was in1930 where 3 dugongs were caught by local fishermen from Mafia Island (Dollman, 1933). Ray(1968) reported Rufiji and Kilwa as the last remaining refuges for dugongs. Recent studies (WWFEAME, 2004; Sallema, et al., 2009) evidenced existence of dugongs between Kilwa – Rufiji – Mafiachannel.Detailed information on animal profile is needed to understand its threats, status ecology
and conservation initiatives.
Methodology
A non-random sampling was used to get 200 respondents in five selected sites, Kilwa, Somanga,Rufiji, Bagamoyo and Dar es Salaam. Respondents were interviewed over the period of fourmonths from July 2008 to February 2009 covering the monsoon periods.
Analysis, Results and Discussion
Abundance and distribution of dugongs in selected sites
Number of respondents, age class, landing sites, number of respondents who reported occurrenceof dugongs between 1950s and 1970s and numbers of live dugongs and sightings since 2000s arepresented in Tables 1, 2 and 3. The abundance of dugongs based on monsoon periods ispresented in Table 4 which is consistence with current responses from fishers on timing sighting ofdugongs. The high abundance of dugongs in the past can be attributed to the fact that the26proportion of dugong population to human pressure on marine resources was high so hunting
dugongs did not show remarkable impacts on their stock. Population increase for the last half
century has multiplied pressure on terrestrial and marine ecosystems. The sharp rise in 2000s canbe to the fact that conservation efforts are increasing. Major remaining areas of dugongs reported
are consistence with studies by (Sallemaet al., 2009) that dugong distribution and abundance isreflected in specific areas characterized by calm seas with clear water and abundance of sea grassbeds. Most dugong areas harbor Halodule uninervis which are preferred food for dugongs. This isconsistence with study by Aragones, 1996 that selection for highly digestible Halophila and highnutrients Halodule means that dugongs maximize nutrient intake rather than bulk. Dugongs use
specialized habitats for calving and mating (Anderson, 1981).

Table 1: Number of landing sites of respondents interviewed
Number of landing sites

SexLocation
Kilwa

4

M43

Somanga4

Rufiji2

Bagamoyo

Age ClassesF
718-451346-702871+
945

51133

620

107212432

8532

3

Dar es Salaam

225

58193Total

16165

3544133

23

Source: Field Work January –December 2008/2009

Table 2: Locations, landing sites, number of respondents interviewed, number of dugong caught
and sighted (1950s – 1970s) Shaded columns (12%, 7%) and (2000s)
Unshaded columns (43.5%, 22.5%)
INTERVIEWS

27

No. ofrespondents
sighteddugongs

112
123
15
1
121
Somanga
1745053230
Rufiji
154150B’moyo
102
200
10
1DSM
15050103TOTAL
200
24
Source: Field Work January –December 2008/2009

No. ofrespondentscaughtdugongs

No. ofrespondentscaughtdugongs

No. ofRespondents

KilwaKivinje
KilwaKisiwani
Olelo
KilwaMasoko
Pwani
NgolweMkokoMmoja
NdumboMohoroKisijuChanguhela
Nchipana
KitameMagogoni
Mjimwema
Mbweni2000s

No. ofrespondents
sighteddugongs

Kilwa

Landing site

Location

1950s – 1970s

02
10
30
20
30
10000
2
14

59951411
17
11
1100
2
10
1
87

2
3
10
92
1
1113100100045

Table 3: Areas with Dugongs
Location
Kilwa
Somanga

Areas With Dugongs
Olelo
Likotonazi
Utigiti
KichinjaMbuzi
PombweKisijuMohoro BayRufiji

No. of dugongs Sighted
111111
1
7

TOTAL
Source: Field Work January –December 2008/2009

Table 4: Fishers’ observations of dugong sightings by months / period:
Unshaded columns = NE monsoon (88%); Horizontal patterns = SE monsoon(22%); Vertical patterns = inter-tropical monsoon periods (88%)
22%

88%

88%

MarchMay

Dec.

Nov.

Oct.

Sept.

Aug.

Jul.

Jun.

May

Apr.

Mar.

Feb.

Jan.

Dugong areas

October toNovember

88%toMonths/periods

Olelo
Likotonazi
Utigiti
KichinjaMbuzi
PombweKisijuMohoro Bay
Source: Field Work January –December 2008/2009

Magnitude of dugong threats and status
Dugongs are still caught incidentally in gillnets (Table 5). Non-selective trawlers kill dugongs
and destruct their habitats. Prawn trawling and dynamite fishing destroy dugong habitats in
Rufijidelta, Jaja and Mchungu

1021105% Killed
3.33
06.7
3.33
3.33
016.66

Total %Killed13.331
3.33
3101
3.33
310Rufiji
310TOTAL
1136.66
Source: Field Work January –December 2008/2009

No. Killedintentionally% Killed

No. Killed
Incidentally

Olelo
Litokonazi
Utigiti
KichinjaMbuzi
PombweMohoro Bay

Total no. ofdugongs
killedKilwa
Somanga

StationLocation

Table 5: Number of Dugongs Killed Incidentally and Intentionally January 2000 – May
2009 and % Killed out of 30 dugongs caught

2
15
2
4
3
16

6.66
3.33
16.7
6.66
13.3
1053.3Involvement of local communities in conservation initiatives of Dugong
Eight Five fishers were imparted with knowledge of dugong conservation in three sites throughworkshops conducted between July 2008 and May 2009.

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Dugong Profile
Eight Two (82%) of respondents had better understanding on dugong. They reported dental
formula of dugong similar to that of herbivores which is consistence to the study by Dollman,
1933 that the first pair of incisors and cheek teeth is shed when animal is growing. The better
understanding on dugong profile can be attributed to respondents have been fishing for manyyears so had knowledge of the area and dugong. This is consistence to previous studies(WWF EAME, 2004; Sallemaet al., 2009) suggesting that previous studies are reliable.
Conclusion
The continued protection of mangroves and other vegetation on the land adjacent to sea
grasses could prevent overloading of sediments which can kill sea grasses. It is recommended
to resurvey the area during northeast monsoon period for possibility of having more sightingsand comparison if dugong sightings will be seen.
Acknowledgements
I am grateful to Western Indian Ocean Marine Science Association (WIOMSA) for financial
support and fishers and Field Assistants for their hospitality and technical support.
References
1. Anderson, P. K. 1981. The behaviour of the dugong (Dugong dugon) in relation to conservationand management. Bulletin of Marine Science 31: 640 – 647.
2. Aragones, L. V. 1996. Dugongs and green turtles: grazers in the tropical sea grass ecosystem.
PhD thesis. James Cook University of North Queensland, Townsville, Australia.
3. Chande, A. I., Mtoka, G. F and Mhitu, H.A. 1994. Marine mammals and fisheries Interactions inTanzania. UNEP
4. Cockcroft, V. G and Krohn, R. 1994. Passive gear fisheries of the South Western Indian andSouth Eastern Atlantic Oceans: an assessment of their possible impact on cetaceans. Report ofthe International Whaling Commission. Issue 15: 317 – 328.
5. Dollman, G. 1933. Dugongs from Mafia Island and a manatee from Nigeria. Natural History
Magazine. No. 28, Vol. IV: 117 – 125.
6. ICUN (The World Conservation Union) 2000. The 2000 ICUN Red List of Threatened Animals.
ICUN, Gland, Switzerland.
7. ICUN (The World Conservation Union) 1990. The 1990 ICUN Red List of Threatened Animals.
ICUN, Gland, Switzerland.
8. Marsh, H., G. De’ath, N. Gribble and Lane, B. 2001. Shark control records hind cast serious
decline in dugong numbers off the urban coast of Queensland. Final report to the Great Barrier
Reef Marine Park Authority, Townsville, Australia.
9. Ray, C.1968. Marine Parks for Tanzania, results of a survey of the coast of Tanzania. The
Conservation Foundation, New York Zoological Society.
10. Sallema, A. E., Mapunda, M. & Lilombero, M. 2009. A Study of Myths, Legends and Scientific
Facts of Dugong in Selected Areas of Tanzanian Coast. Markad Printers 30pp.
11. WWFEAME. 2004. Towards a Western Indian Ocean Dugong Conservation Strategy: The
status of Dugongs in the Western Indian Ocean Region and Priority Conservation Actions. Dares Salaam, Tanzania: WWF. 68pp.

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