- MAÑGROVE EcosYsTEM REsEARCH DIVIsIoÑÏ(MERpj
Trang 2WETLAND EXPLOITATION AND UTILIZATION IN TAM GIANG - CAU HIAI COASTAL LAGOON: IMPORTANCE AND CURRENT STATUS
INTRODUCTION
Tam Giang - Cau Hai Lagoon is one of the important coastal wetland groups in Vietnam It is of great importance in terms of biodiversity value, natural resources, environmental and ecological functions and socio-economic development of Thua
Thier Hue Province
Population and economic pressure has created
serious threats to the area Therefore, it should be soon protected In recent years, Hai Phorig Institute of Oceanology has coordinated with the Departinent
of Science, Technology and Environment of Thua Thien Hue Province to carry out surveys on the wetland A part of the results obtained from the surveys will be presented in this paper
I LOCATION, SCOPE AND TYPES OF THE WETLANDS
1.1 Location
The wetland area of Tam Giang - Cau Hai Lagoon lies between 16°14’-16°42’ N and 107°22’-
107°57’ E spreading over an area of 70 km in
length along the coast of Thua Thien Hue It is 7
km northeast of Hue City The wetland area belongs to the 5 districts of Phong Dien, Quang Dien, Huong Tra, Phu Vang and Phu Loc
1.2 Scope and types of the wetlands
Tam Giang - Cau Hai Lagoon typifies the lagoon
wetlands in the monsoon tropics, which is large in
scale in the world and the biggest in Southeast Asia Based on the data collected from the field trips and interpretation of satellite images, 10 types belonging
to 4 groups of wetlands with the total area of 24,876 ha have been recorded The group of vegetated wetlands occupies 4,580 ha including mangrove and
grass wellands and some types of wetlands on which
tice is occasionally farmed The group of non-
vegetated wetlands 282 ha in area includes tidal mud
and sand flats The permanently submerged wetlands
with an area of 19,435 ha include water grass bed,
Tran Duc Thanh", Nguyen Chu Hoi’, Do Nam™, Nguyen Mien”, Nguyen Huu Cu", Nguyen Van Tien’,
Tran Dinh Lam”
muddy substrata, sandy and muddy substrata and river bed Other group of wetlands (579 ha) comprises aquaculture ponds, Water grass bed int the whole area
makes up 12,200 ha including algae, scaweed,
brackish water and fresh water Their distribution depends on seasons and the closure of Tu Hien Inlet (Thanh et al., 1998)
Il, SIGNIFICANCE
1.1 Value
1.1.1 Biodiversity
Tam Giang - Cau Hai Lagoon is rich in gene
with 912 species (Thanh ct al., 1998) of which
Phytoplankton accounts for 265 species belonging to 6 phyla namely Bacillariophyta, Chlorophyta, Dinophyta and Euglennophyta Notably, there are
6 species of toxic algae belonging to Dinophyta
Bacillariophyta phylum represents 70.1% of the
total species There are 54 species of Phytobenthos
belonging to Bacillariophyta 46 seaweed species
can be found belonging to 3 phyla Cyanophyta,
Cholorophyta and Rhodophyta Hydrophytes found in the area are composed @f 15 species of which
there are 6 sca-grass species namely Halophyla ovalis, H beccarii, Halodule pimifonia, TH uninervis, Cymodocea rotundata and Ruppia maritima Of 66 species of zooplankton found,
Copepoda alone accounts for 46 There are 76
species of zoobenthos of which polychacte occupies 11, small crustaceans 16, mollusc 19 and economic cruataceans (shrimps, crabs) 30 There
are 230 fish species Fish families with many species are Cyprinidae, Mugiidae, Gobiidac, Eugraulidae, Scrranidac and Lutianidac Six specics recorded in the Red Book of Victnam are Clupanodon thrissa, Clupanodon punctatus,
Angguilla japonica Angguilla marmorala, Ophiocephalus striatus and Nematalosa nasus)
Birds found in the area account for 73 species
belonging to 53 genera and 29 familics, of which there are 34 native specics and 39 migratory
species, Limnodromus semipalmatus are recorded in the Red Book of Vietnam and 30 species are in the strict protection list of the Council of Europe * Dr Tran Duc Thanh, Assoc Prof, Dr Nguyen Chu Hoi, Dr Nguyen Huu Cu, Dr Nguyen Van Tien, Tran Dinh Lam Iai Phong Institute of Oceanology
“Do Nam, Nguyen Mien, Department of Science, Technology and Environment of Thua Thien Hue Province
54
Trang 3(Council of Europe,1995) In winter, over 20,000
waterfowls gather in sanctuaries in such lagoons as
Cua O Lau, Cua ‘Dai Giang and Dam Sam Dominant waterfowls with a high number of individuals are [7ulica atra, Anas poechilorhyncha,
-Inser anser, lgretta garzetta, Bubulcus ibis and
„lrdea cinerea
Tam Giang - Cau Hai Lagoon Wetlands are endowed with many ecosystems such as estuarine
ecosystem, alga - sca-grass ecosystems, mangrove
ecosystem, agricultural ecosystem, soft bottom
ecosystem and marsh ecosystem In addition,
lagoon inlet ecosystem and sandy ecosystem off the lagoon exist here
Different types of marshes, mangrove flats, tidal
flats, mud flats, estuaries, sca-BrASS beds, soft
substrate mound, agricultural land, aquaculture ponds and creeks are indicative of the habitat
diversity in the area It is habitat diversity that has created the diversity of communities living on these
habitats
Biodiversity is also indicated by the diversity of species sources from fresh, brackish and sally waters Species of fresh water origin come mainly from rivers and lakes into the lagoon, especially in the rainy scason Salty water species come from the
sca Brackish water specics including fresh water or marine species which are able to adapt to brackish water settle in the lagoon This group accounts for the largest number
1.1.2.Aquatic living resources
Many aquatic species are of high economic value About 1000 tons of high economic value fish (20 - 25 species) are exploited annually Main fish species of cconomic value are Cyprinus centralis, Mugil cephalus, Pomadlasy — macculatus,
Oxyurichtys tentacularis, Arvgyrosomus argentatus, Ancho sp Clupanodon punctatus, Siganus guttatus, Siganus oramin and Epinephenus
Suscoguttatuss
Of the 12 shrimp and crab species of economic value found in the lagoon, Penaeus monadon, P.merguensis, Metapenaeus ensis and Scylla
serrata are typical Catching and aquaculture
shrimp and crabs hold 1/3 of the total fishery
products of the lagoon Molluscs are also economically important, especially Corbicula
subculcata, Meretrix meretrix and Mytilus viridis Corbicula subsulcata is mainly found in Tam Giang with the stock of 4000 tons
Alga species of economic value are Gracilaria tenuistipitata (with a yield of up to 5000 tons of dry
weight per year) and G.asialica At present,
exploited and cultured Gracilaria output is about
400 tons of dry weight/a ycar being used as food, herbal medicine and in industry Caloglossa ogasawareansis is used as helminthes medicine but its natural reserve is small Some species of algae and seaweed are intensively exploited, estimated at
150,000 tons/year being served as fertilizers and
food for cattle, Many species of waterfowls arc of high economic value Yet, they shouldn't be hunted
Before 1975 shrimp and fish output in the lagoon reached 4500 - 5000 {oiis/year At present, 2500 tons of shrimp and fish/year are naturally
* exploited
1.1.3 Port transportation
Boating is a good way for half a million people in the 5 districts surrounding the lagoon Everyday,
busy boats carrying passengers and goods run safely and economically Tan My Port situated in the lagoon plays an important role in socio- economic development The port capacity is now enough for 500 - DWT ships, but till the year 2010,
as planned, it will be for 3000 - DWT ships 1.14 Marine — exploitation and infrastructure
Tam Giang - Cau Hai Lagoon is the key place where marine fisheries of Thua Thien Hue Province is practiced Many fishing harbors are located along » the lagoon shore At present, the average capacity of marine fish catching ships is only 19.7 hp / ship
while some of the fishing harbors have enough
capacity for fishing boats of over 100 hp Tam Giang - Cau Hai has a high potential for off-shore
fishing development It is the fishing harbors and sca-product processing bases that create jobs for
many coastal inhabitants Frozen marine products
of Phu Vang Districtealone brought in 24.3 billion VND in 1997
1.1.5 Agricultural development
The lagoon wetlands have an indirect value but
are of great importance to the development of agriculture on an area of 54,300 ha of which 37,700
ha are rice cullivated land The wetlands play a role in climatic regulation, flood and salt intrusion control through their ability to balance water and
maintain under ground water A considerable area of the lagoon wetlands is used for occasional rice farming with a low, productivity (1.5 ton/ha/year)
Every year, a high volume of water grass is used in husbandry and cultivation A large number of cattle
(buffaloes, cows) and poultry (ducks) is tended in the lagoon
1.1.6 Tourism, entertainment
Together with Thanh Noi - a world culture heritage and Bach Ma National Park, Tam Giang - Cau Hai Lagoon is also an ideal entertainment and
tourist resort with many vivid features With waterfowls and sca-grass beds, the arca has a high potential for eco-tourism (swimming, diving and entertaining) Cultural heritage, historical placcs, festivals and traditional professions are potential for
tourism
1.1.7 Settlement value
Rich resources and healthy environment have created favorable conditions for the community of 300,000 people living along the lagoon and 10,000
Trang 4people settling in the area, creating a settlement
value of the community living on agriculture and
fisheries
1.1.8, Scientific and educational value
The lagoon wetlands are ideal places for education, (raining, and scientific research It is where students and scicnlisis have chosen various
topics for their graduation, post graduation and
dissertations Tam Giang - Cau Hai has potential for scientific research on geomorphology, geology, ecology, biological resources, environmental management, coastal dynamics and socio - economic issues This area is convenient for the organization of national and scientific workshops held in Hue and the experimental implementation of high-tech aquaculture models
1.1.9 Cultural value
Traditional customs and festivals are of aesthetic, cultural and spiritual value They are closcly attached to production, occupations, fishing gears and ways In addition, the lagoon and its surrounding arca contain cultural, historical and archeological places worth being conserved
1.2 Functions
1.2.1 Environmental function
The Tam Giang - Cau Hai Lagoon Wetlands play a very important environmental function related to the community life (300,000 peoplc) in a large arca of 94,000 ha The wetlands have 3 basic functions:
- As a large lake able to regulate micro climate
and control flood, storm surges and salt intrusion - Maintaining underground water in relation to
underground water table used for daily life and
production, restricting drought and sand flying and over - washing from the sand dunes
- Storing and burying wastes and self-cleaning
the environment
1.2.2 Ecological and habitat functions
Nutrient content and primary productivity in the lagoon are much higher than and "exported" to the coastal marine area The primary productivity in the
wetlands is high as the sca-grass beds cover half the area of the lagoon with high biomass and sca-grass communities are able to develop and regenerate rapidly and seasonally Especially, algae and sea
grass are food for many fishes of high economic
value creating a short food chain with high biological productivity Habitats in the lagoon serve as shrimp and fish spawning and nursing grounds, supplying both the lagoon and sea with stock and boreal
migrants with a refuge (about 20,000 individuals in
winter)
1.2.3 Protection function
In addition to the function of flood, storm
surges and salt intrusion control, the lagoon is a
safe shelter for boats and ships from strong wind in storms Each time a storm hits the area, hundreds or
even thousands of ships and boats refuge in the
lagoon,
1.2.4 Production and supply function
Every year, the lagoon provides 2,500 - 3,000 tons of aquatic products, 150.000 tons of water grass Thousands of buffalocs and tens of thousands of ducks are (ended here Nearly 130,000 people exploit aquatic products in the arca annually On average there is one fishing gear in an arca of 2.5 ha and fishing means in an area of 4.3 ha Aquaculture land in the lagoon makes up 1,500 ha -Marshes along the lagoon are reclaimed for rice cultivation The wetlands create work and products for laborers Of the 300.000 people along the lagoon, 195,000 people and 3,900 houscholds are
close to the lagoon products, 7.500 laborers specialize in exploiting the lagoon, 3.200 houscholds with 5,000 labors use il as a base for marine fishing and owe 22,000 ha of rice in surrounding arca in relation to the lagoon wetlands in respect of environmental conditions (Hai Phong
Institute of Occanology and Service of Science,
Technology and Environment of Thua Thien Huc
Province, 1996) 1.3 Role
As a transitional zone between the sea and land, the wetland area also plays a part in the balance of
coastal ecosystem and nature
The role it plays in socio - cconomic
development of Thua Thien Hue Province is great It plays an important part ifPthe formation of the lagoon inhabitant communitics with their own properties of custom, daily activitics fishing gears,
traditional festivals, ctc It is the lagoon that helps form the lagoon cconomy including agriculture, irrigation, transportation, forestry and fishery
“Il EXPLOITATION AND UTILIZATION
STATUS AND URGENT PROBLEMS
2.1 Overexploitation and habitat destruction
Aquatic products in the lagoon sharply declined
by 40.2% from 4.515 tons in 1973 to 2,700 tons in 1997, Some species (Aforingua sp., Afacrura reevesii ) are in danger of extinction The productivity of exploited marine products reduced from 0.79 ton a boat/a year in 1990 to 0.58 ton a boat/a year in 1997,
Overexploitation and destructive exploitation
due to population pressure, demand for
cmployment and attraction of recent aquatic exports are the main reasons behind the decrease In the
lagoon, aquatic exploitation attracted 5.500 laborers in 1982 and over 9,000 people in 1997,
Aficr 7 years (1990 - 1997) catching boats increased by 61.5% from 3,110 boats to 4.675
boats, of which motor boats rose by 76.6% (from
Trang 5uring the period of 13 years (1984-1997), the
r of fishing weirs increased from 450 to
(125 sets/a year)
addition to the high density of fishing means
1.3 ha of water surface) and fishing gears (1 ‹s ha of water surface), destructive tation by using dynamite, electric power and
nets with meshes smaller than the permission mm in size are common The hunt for birds
to increase
hie development of fixed fishing gears such as apong, trapper of bamboo, dip-net, ctc and smbankment of aquaculture pond cause not traffic stagnation but also reduction in water ange — sclf- cleaning, ability, leading to ronmental pollution and uneven distribution of ient and seed sources Habitats and natural iscape are destroyed by some kinds of
‘oitation occupations with the utilization of ders, clectric tools, rakes, etc., the activitics of
ing boats and ship, transportation, pond making
\ agricultural reclamation As a result, besides loss of landscape beauly, substrata are tumbled;
ac and walter grass decrease in area and erage; mud flats and shelters are being narrowed
reasingly
1, Environmental pollution
In general, according to the norms of DO, BODs id COD, the water environment quality is still
gh and not yet polluted on a large scale However,
nuy Tu and Cau Hai Lagoons show signs 0Ÿ
‘lution The indexes of BOD; and COD tended to
icrease between 1993 and 1998 The average alue of DO is 5-8 mg/l; CDO - 2.9 mg/l; BOD; -
3 mg/l Oil pollution is at an alarming level Most
f water samples exceed the allowed oil oncentration set for tourism (0.3mg/l) or even
¡#mg/1 This results Írom the inadequate
nanagement of the activilics and equipment
supplying oil in the lagoon (Thanh ct al., 1998)
The metal content (Cu, Cd, Zn, Hg) is much lower
than the standard level However, Cu and Cd show a sign of higher content Although pesticide content
is much lower than the allowed standard level, ín water, soil and organism body, there is a redundant content of six kinds of pesticides (HCB, Aldrin, Endrin, DDD, DDE and DDT) The key waters of
the lagoon hasn't been polluted with coliform yct However, the coliform content along the shore ncar the residential arca and markets exceeds the
allowed standard level of 1000 MNP/ 100 ml (Hoi etal., 1996)
2.3 Natural changes
Some natural hazards, which are also
complicated by human activities, are as follows:
57
- shoaling water body, fying and over-washing sand
- inundation and desalling water
~:droupht and salt intrusion - moving and closing inlets
Shoaling water body going on continuously has contributed to degrading the lagoon, desalting
water, inundation, moving and closing the inlets The area suffers from drought and salt intrusion every year causing damage t9 agricultural production and local life Inundation results in the greatest loss for the lagoon cconomy, environment and local life Unusual inlet moving and closing and water shoaling lead to a number of subsequent consequences such as salt intrusion, flood, water desalting affecting the living condition and the regional economy (Hoi et al., 1996)
2.4 Conflicts of lagoon wetland use
Conflicts of lagoon wetland use are intensifying
disputes over resources, space, investment and
adversely affecting the environment, That is the contradiction between port transportation and fisheries, irrigation work and fisherics, agriculture and fisheries, salt intrusion prevention and flood
control, individuals and communities and protection and development
2.5 Threats to the lagoon
The lagoon environment and resources will be
seriously threatened if they are not well protected
and managed Pollution caused by daily rubbish,
oil, heavy metals and pesticides tends to increase Nutrients in the lagoon are on the decrease due to the operation of irrigation works in the upper basin Eutrophication and red tide- toxic alga phenomena
are potential threats to the lagoon In the lagoon, 6 species of toxic algae have been found Overexploitation and indiscriminate aquaculture
result from population pressure and demand for jobs Habitats are increasingly destroyed duc to the exploitation of the lagoon especially waler-grass
and algac exploitation and agricultural reclamation
Unusual inlet moving and closing ata gradually rapid rhythm is caused by large-scale climatic and hydrological disturbance, changes in water distribution and balance affected by the catchment arca, Water turbidity, shoaling and desalting due to the natural evolution are worscned by human
impacts
Ill, CONCLUSION
Trang 6plays an important part in ecological biological and hydrological sustainability The functions of the wetland area are to regulate climate, to control flood, salt intrusion and storm surge to maintain
underground water for immense sandy plains to
create favorable conditions for water way traflic to
shelter thousands of boats and ships from storms and strong wind and to provide coastal waters with
nutrients and stock The lagoon wetland arca is a
coastal productive and bio-diverse ecosystem and rich in aquatic living resources Therefore the lagoon is a good living environment for the 300,000 local people and has a great cffect on the socio- cconomic development of the area
According to the Ramsar Convention (Ramsar Convention Bureau 1997) Tam Giang - Cau Hai is
worth being recognized as a wetland areca of
international importance (Ramsar site), Nevertheless, the pressure of population growth and
economic development Icads to the status of
overexploitation and habitat destruction causing a decrease in biodiversity and aquatic resources and environmental pollution The conflict of resource
utilization and natural changes in the wetland area secs {o be on an increase Therefore the
establishment of the wetland-protected area in Tam
Giang - Cau Hai Lagoon is an urgent need
REFERENCES
Council of Europe, 1995 Convention on the conservation of European wildlife and natural habitats Convention Ny Ll Hai Phong Institute of Oceanology and Departnent of Science, Technology and Environment of ‘Thua Thien Hue, 1998
Conservation values of Tam Giang - Cau Hai Lagoon Wetlands
ientific and technological information, number 3 1998 Departinent of Science, ‘Technology and Environment of Thua Thien Hue Province: 76-87 (in Vietnamese) Hoi, N.C eb al., 1996, Research into exploitation and rational utilization of Tam Giang Lagoon potential Scientific reportof
the project KT DL 95 09 stored at Hai Phong Institute of Occanology (in Vietnamese)
Ramsar Convention Bureau, 1997 The Ramsar Convention Manual: a Guide to the Convention on Wetlands (Ramsar, Iran,
1971), 2nd ed Ramsar Convention Bureau, Gland, Swizenland: 1-161
Thanh, T D., N TL Cu and T 1D, Lan, 1996 Protection and Management of Lagoon Wetlands in the Central Coast of
Vietnam In: Nguyen Chu Hoi (cd.) Vietnam National Wetland Conservation and Management Strategy Status,
Utilization, Conservation and Management Wh ‘orkshop Proceedings, SIDA IUCN:MOSTIENEA Hanoi: 48-54
Vhanh, ‘T D., ct al., 1998, Estimation of potentials and the proposal to establish a protected arga of Tam Giang - Cau Hai
Trang 9SOME PICTURES OF TAM GIANG - CAU HATLUAGOON
Photo: Tran Duc Thanh
~ Figure 2 The ground of black coots (Mulia atra) in” the lagodn
Figure 3 Fish catching by
drip-net in the lagoon