Cl^A DAI (QUANG NAM) VA DAO PHU QL^Y (BINH THUAN) Nguyen Van Quan
L M O DAU
Tham cd bien dugc danh gia la mdt trong nhirng he sinh thai biin nhiet ddi giau cd nhat ve da dang sinh hgc sau hf sinh thai ran san hd va rimg ngap man. Cac sinh vat sdng kem trong cac tham cd bien, dac biet la nhdm ca cd nhiing dac diem sinh hgc rit dac thii so vdi cac he sinh thai khac, vi le tham cd biin vira la noi cung cip thirc an vira la bai de cho nhieu loai hai dac san khac. Them vao dd, cac tham cd bien cdn ddng vai trd quan trgng nhu la noi chuyen tiep trong vdng ddi cua nhdm ca va sinh vat sdng kem giira he sinh thai cd bien vdi cac he sinh thai khac nhu san hd, rimg ngap man, gdp phan tao ra su phirc tap trong cau tnic mang ludi dinh dudng ciia bien nhiet ddi (Bertness et al, 2001).
Tuy nhien, cho tdi nay cac nghien cim ve ngudn lgi ca trong tham cd bien d Viet Nam cdn rat khiem tdn. Phan ldn cac nghien cuu mdi chi nam trong khudn khd cac de tai dieu tra khao sat ve ngudn lgi cd bien Viet Nam ciia cac tac gia Nguyen Van Tien (1999-2006), Nguyen Hiiu Dai (2002), Nguyen Van Quan (2006). Khu vue ven bilri mien Trung da dugc cac chuyen gia nghien cim ve cd bien danh gia la khu vuc phan bd cua cac tham cd bien quan trong, khdng nhiing cd y nghTa to ldn ve mat khoa hoe ma cdn la ca sd tao ra cdng an viec lam cho hang van ngu dan sdng phu thude true tiep va gian tiep vao ngudn lgi ma tham cd bien mang lai. Trudc bdi canh dd viec dat ra nhiem vu nghien cim ngudn lgi ca trong mot sd tham cd bien trgng diem nhu Cira Dai (Quang Nam) va dao Phii Quy (Binh Thuan) trong khudn khd de tai "Dieu tra ngudn lgi tham cd bien Viet Nam, de xuat phuong hudng va cac giai phap hiiu hieu sir dung ben viing ngudn lgi" do Vien Tai nguyen va Mdi trudng bien tien hanh nam 2006 se la nhung ddng gdp budc dau cho viec nghien cuu ngudn lgi ca trong tham cd bien.
Bai viet nay nham cung cap nhimg ket qua nghien ciiu budc dau ve hien trang ngudn lgi ca trong tham cd bien Cira Dai va dao Phii Quy phuc vu cho cdng tac quan ly sir dung hgp ly ngudn lgi cac tham cd bien Viet Nam trong thdi gian tdi.
II. TAI LIEU VA PHU'ONG PHAP NGHIEN ClTU 2.1. Tai lieu
Tai lieu sir dung trong bao cao nay la toan bd mau vat va tu lieu trong chuyen khao sat thang 5/2006 tai cac dia diem khao sat thugc khu vuc Cira Dai va dao Phii Quy.
2.2. Phtfong phap nghien curu
De thu thap mau vat va tu lieu cac can bd thuc dia da sir dung cac phuang phap thu mau sau: (1) Sir dung ludi gia keo ca tren cac tham cd bien vdi thdi gian keo ludi la 1 gid. Toan bd sd mau vat cd trong me ludi dugc chup anh tai chd va cd dinh trong formalin ndng do 30% va chuyen ve phdng thi nghiem ciia Vien Tai nguyen va Mdi trudng bien; (2) Thu mau vat ciia cac tau thuyen danh ca tai cac khu vuc nghien ciiu; (3) Sir dung phuang phap dieu tra nhan dan tai cac tau thuyen neo dau tren cac tham cd bien va tham cac chg ca gan dia diem nghien ciru. San lugng khai thac (mat do, khdi lugng) dugc thu thap tren co sd sd lieu thdng ke ciia
Nguyen Van Quan
cac phdng ndng nghiep dia phuong va sd lieu thdng ke tren me ludi danh ca thi nghiem tai dia diem nghien ciiu.
Mau vat va cac biic anh chup tieu ban dugc Itm trii va phan tich trong phdng thi nghiem cua Vien Tai nguyen va Mdi trudng bien. Ten khoa hgc va ten ddng danh (synonym) cua ca dugc tham tra theo Beaufort (1940, 1941); Carcasson (1977), Chevey (1934), Chu et al (1962, 1963), Thi (1991), Dinh va Thi (1985), Nelson (1994), De Bruin et al (1994), Allen (2000), Eschmeyer (1998), Nakabo (2002) va tham khao them phan mim Fish Base 2004 (Froese and Pauly, 2004).
III. KET QUA NGHIEN ClTU 3.1. Thanh phan loai
Tap hgp ket qua phan tich mau vat va tu lieu da xac dinh dugc 72 loai ca thugc 55 gidng trong 41 hg cd trong cac tham cd bien thugc pham vi nghien ciiu. Dac diem dac trung cua khu he ca dd la su kem da dang ve sd loai trong mdi hg the hien mgt each ro net vdi 6 hg cd sd lugng loai dang ke nhat do hg ca phen (MuUidae), ca bang chai (Labridae), ca dia (Siganidae), ca lugng (Nemipteridae), ca khe (Carangidae), ca mii (Serranidae) mdi hg cd 4 loai chiem 5,6% tdng sd loai dugc phat hien. Ke tiep do la cac hg ca mdi (Synodontidae) va ca mdm (Gerreidae), mdi hg cd 3 loai chiem 4,2% tdng so loai dugc phat hien. Cac hg cdn lai cd sd lugng loai tir 1-2 loai.
So sanh ve phan bd sd lugng loai giiia cac dia diem khao sat dugc tien hanh trong khudn khd cua de tai vdi ket qua nghien cuu cua cac tac gia khac da tien hanh d khu vuc mien Trung va Nam Bg cho thay (Bang 1) khu he ca trong khu vuc nghien cuu cd tinh da dang kem hon cac vimg bien khac d khu vuc mien Trung (Nha Trang) va Nam Bo (dao Phii Qudc). Dac biet vimg bien dao Phii Quy noi tham cd bien phat trien tuong doi tdt lai cd sd lugng loai thap nhat so vdi cac khu vuc khac.
Bang 1. Phan bo so lu-grng loai cd trong tham co bien khu virc mien Trung va Nam Bo
STT1 2 3 4
Tham co bien Quang Nam
Nha Trang (dam Thiiy Trieu) Dao Phii Quy
Phii Quoc
So Itforng loai 51*
87**
23*
91*
Nguon: *Nguyen Van Quan (2006), **Nguyen Hiru Dai (2002) 3.2. Cau true dinh dirong va phan bo theo sinh canh
Dua vao tap tinh an va dac diem phan bd trong cac tieu sinh canh (micro-habitat) cua cac tham cd bien cd the phan chia quan xa ca trong tham cd thanh cac nhdm chinh nhu sau (Hinh 1).
Nhom cd sdn moi'. cd 11 loai chiem 24% tdng sd loai ghi nhan, tap tnmg d cac hg ca
Mu Serranidae, hg ca Mdi Synodontidae, ho ca He Lethrinidae, hg ca Kem
Haemulidae... chiing thudng sdng an nap trong cac hang hdc dugc tao ra bdi cac bui cd
(ca mii, ca kem) hoac cd mau sac nguy trang phii hgp vdi mau sac cua gia the (la va
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than cd) de chu ddng rinh bat mdi mdi khi cd con mdi boi qua.
Nhom dn co: cd 6 loai chiem 13%, dai dien bdi hg ca Dia Siganidae, ho ca Ddi Mugilidae, hg ca Bang chai Labridae. Chiing sir dung la cd, hat, re hoac rong tao de lam thirc an va da timg dugc vi nhu nhdm "kiem soat su phat trien cua rong tao" d he sinh thai ran san hd (Sale 1991). Trong he sinh thai cd bien chung cdn cd vai trd "di gidng"
cd bien sang cac khu vuc lan can thdng qua viec phat tan hat hoac cac phin than rl ma chiing khdng sir dung nhd sdng va ddng chay.
Nhom ca an co 13%
Nh6in ca Sn tap 6 3 %
Nhom ca san moi 2 4 %
Hinh 1. Cac nhom dinh dirong chii yeu cua quan xa ca trong tham co bien Nhom dn tap: cd 29 loai chiem 63%, nam tap trung trong cac hg ca Phen Mullidae, hg ca Son Apogonidae, ca Lugng Nemipteridae, ca Mdm Gerreidae,... Phin ldn chimg la cac nhdm ca an tren nen day cua cac tham cd bang each "dao bdi" nen day de an nhuyen the (ca phen) hoac cd su thay ddi ve khau phan an giiia ddng va thuc vat nhu hg ca Lugng, ca Son va ca Mdm.
Vdi dac diem cau thanh cua cac nhdm ca trong cau tnic dinh dudng cua quan xa ca trong tham cd bien ciing phii hgp vdi cac ket qua nghien cuu d cac viing khac: nhdm ca an cd chi chiem 13% trong khi nhdm ca an tap chiem tdi 6 3 % tdng sd loai, dilu nay thi hien vai trd cua tham cd bien khdng nhirng chi cimg cap ngudn thiic an true tiep cho cac ho ca an thuc vat (sir dimg re than va la cd lam thiic an) ma cdn gian tiep cung cap ngudn thiic an cho nhdm ca an tap la nhdm sinh vat day sdng kem trong tham cd bien.
Nhdm ca san mdi (nhdm ca vang lai do cd kha nang boi lgi va di chuyen nhanh) vdi ty le cao tdi 24% ciing la minh chiing cho thay tham cd bien la noi kiem an cua cac hg ca cd kich thude ldn trong bae thang dinh dudng, noi ma nhdm ca mdi cd sd lugng ca the ldn tap trung trong tham cd bien. Mat khac, ciing cd the day la mgt bang chung cho viec cac tham cd bien la noi uong nudi au triing cua nhdm ca san mdi trudc khi chiing trudng thanh va di cu sang cac habitat khac nhu: ran san hd va rimg ngap man.
So sanh giiia cac tham cd bien Cira Dai (dai dien cho vimg nude ven bd) va dao Phii Quy (Binh Thuan, dai dien cho vimg dao xa bd) ciing the hien rd sir khac biet vl
Nguyen Van Quan
cau tnic thanh phan loai. Vimg Ciia Dai, nai ma loai cd luon NTiat Ban Zosterajaponica chiem uu the phat trien thanh nhiing tham day la nod phan bd ciia cac nhdm ca cd kich thuoc tuong ddi nhd nhu ca cang vach Pelates quadrilineatus, cac dan ca dia an cd tap trung thanh dan Siganus fuscescens vdi sd lugng len tdi hang tram ca the. Cac tham co bien dao Phii Quy la nod phan bd im the cua cac loai cd nan bien Syringodium isoetifolium, cd bd bien Thalassia hemprichii, cd he ba rang Halodule uninervis lai la noi phan bd cua cac nhdm loai ca cd kich thude co the ldn nhu ca dudi d Raja sp, ca mii Epinephelus coiides, E. fasciatus, ca md Scams rivulatus... mac dii sd lugng loai phan bd khdng nhieu nhimg sinh lugng lai ldn hon so vdi vimg Cira Dai (Quang Nam).
3.3. Danh gia tiem nang nguon loi
Nhu phan tren da trinh bay tinh chat phan bd theo sinh canh cua nhdm ca phu thuoc rat nhieu vao nhdm loai cd bien dac thu cho timg tham cd bien. Xet ve mat ngudn lgi ca trong tham cd bien khu vuc nghien cuu chiing ta phai ke den ngudn lgi ca lam thuc pham cho ngu dan sinh sdng ven bd. NTidm ca dugc khai thac chii yeu la nhdm ca co kich thude CO the ldn, cd gia tri kinh te cao nhu hg ca mii Serranidae (4 loai), ca hdng Lutjanidae (2 loai), ca trap (1 loai), ca dia (4 loai)... day la nhiing nhdm ca dugc khai thac bdi cac loai phuong tien danh bat cd cdng suat nhd ven bd va la ngudn thu nhap chu ylu cua hang tram gia dinh sdng quanh khu vuc nghien ciiu. Theo bang phan loai cac nhdm ca day sdng trong tham cd bien cd gia tri kinh te cao cua cac chuyen gia UNEP lap nam 2006 (Bang 2) thi hau het cac tham cd bien trong khu w e nghien ciiu deu cd nhiing dai dien cua cac ho liet ke trong bang nay.
Bang 2. Hien trang nguon loi cac nhom loai ca day co gia tri kinh te cao trong tham co bien (pliong theo dl xuit ciia UNEP, SCS 2006)
Ten tieng Anh Yellow grouper Chocolate hind
Big eye snapper Brownstripe red snapper
Palefin threadfm bream
Mottled spinefoot
Streaked spinefoot
Greater lizard fish Snake fish
Ten Khoa hoc Epinephelus awoara Cephalopholis boenack
Lutjanus lutjanus Lutjanus vitta
Nemipterus thosapomi Siganus fuscescens
Siganus javus
Saurida tumbil Trachinocephalus myops
Ten Viet Nam Ca mii vang
Ca song chuoi Ca hong dai den Ca lugng vay duoi dai
Ca dia tro
Ca dia xanh
Ca moi thudng Ca mdi cham hoa
Hien trang Rat it gap
It gap, san lugng con 10-20% so vdi nhimg nam 1990
It gap, thinh thoang mdi gap trong me ludi San lugng con 10% so vdi nhung nam 1990 San lugng khong thay doi
San lugng khong doi nhung CO ca nho hem trudc
San lugng khong doi nhung CO ca nhd hem trudc
San lugng khong thay doi
San lugng con 30% so vdi nhung nam 1990
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O khu vuc Cira Dai, theo ket qua phdng van ngu dan danh bat ca trong viing thi toan khu vuc Cira Dai va Sdng Thu Bdn cd khoang 100 thuyen cd cdng suat nhd dudi 20 CV chuyen lam nghe danh bat tren cac tham cd bien. Hinh thirc danh bat chu yeu la gia don ket hgp vdi ludi ben. Nang suat danh bat cd xu the giam di rat nhieu. Trong nhirng nam 1990 san lugng danh bat tren 01 ha cd the dat tdi lOOkg/ha tham cd (san pham gdm ca trap, mii, phen, liet, udp va cac loai ddng vat nhuyen the) nhung cho tdi nam 2006 san lugng chi cdn dat 25-30kg/ha tham cd trong khi dd thanh phan ca tap it cd gia tri kinh te (chu yeu lam thiic an cho gia siic) cd chieu hudng tang len trong cac me ludi.
Ngudn lgi ca tren cac tham cd bien viing dao Phii Quy dang cd nguy co bi can kiet do phai ddi mat vdi cac phuong phap danh bat huy diet: tai huyen dao Phii Quy hien cd 478 chiec tau xudng nhd tir 20 ma lire (CV) trd xudng, chu yeu hoat ddng khai thac hai san d viing ven dao tren nhiing bai cd bien. Ngu dan sir dung nhieu phuang phap danh bat hiiy diet (danh bat bang min, chat nd, hda chat ddc, v.v). Phuong thiic danh bat huy diet nay ngay cang tinh vi hon, da pha hiiy cac bai cd bien, ma hien nay chua cd cac bien phap ngan chan. Viec khai thac thu nhat cac loai trai dc, hai sam, sao bien, v.v. sdng tren cac bai cd dien ra hang ngay.
IV. KET LUAN
Da xac dinh dugc 72 loai thugc 55 gidng trong 41 hg cd trong cac tham cd bien thuoc khu vuc Cira Dai (Quang Nam) va dao Phu Quy (Binh Thuan). Budc dau cung cap nhiing dan lieu co ban ve dac tnmg khu he ca trong tham cd bien ciia khu vuc nghien cuu.
Cau tnic dinh duong cua quan xa ca trong tham cd vdi nhdm ca an tap chiem uu the la mdt trong nhiing minh chiing cho kha nang bao dam cung cap ngudn thiic an va noi d da dang cua cac tham cd bien vdi nhiing mdi lien ket ve chudi thiic an phiic tap ciia cac nhdm loai trong he sinh thai cd bien.
Ngudn lgi ca trong cd bien cua khu vuc nghien cuu chu yeu tap tnmg vao nhdm ca cd gia tri thuc pham cao, cd kich thude co the ldn la co sd cho phat trien nghe danh bat hai san ven bd. Tuy nhien su suy giam ve san lugng va su gia tang ve ty trong ciia nhdm ca tap trong cac me ludi trong thdi gian gan day chinh la hau qua cua viec khai thac ca qua miic bdi cac bien phap khai thac ca hiiy diet.
De dam bao cho viec khai thac va sir dung ben viing ngudn lgi hai san can sdm cd nhirng quy hoach chi tilt va cac bien phap bao ve kha thi cac tham cd bien trgng diem ven bd Viet Nam. Trong dd nang cao nhan thiic cdng ddng ve bao ve mdi trudng va chuyen ddi sinh ke can phai xem nhu nhiing nhiem vu uu tien cua dia phuang trong thdi gian tdi.
TAI LIEU THAM KHAO
1. Allen G (2000). Marine Fishes of South-East Asia. Western Australian Museum.
Periplus Editions, Hong Kong, p. 1-350
2. Beaufort LF (1940). The Fishes of the Indo - Australian Archipelago, Vol. 8, pp.
16-326.
3. Beaufort LF (1951). The Fishes of the Indo - Australian Archipelago, Vol. 9, pp. 1-398.
Nguyen Van Quan
4. Bertness MD, Gaines SD and Hay ME (2001). Marine Community Ecology.
Sinauer Associates, Inc.
5. Chu YT et al (1962). The Fishes of the South China Sea. Peking Science Publishing House, pp. 626-833 (Chinese)
6. Chu YT et al (1963). The Fishes of the East China Sea. Peking Science Publishing House, pp. 356-451 (Chinese)
7. De Bruin GHP, Russell BC and Bogusch (1994). The Marine Fishery Resources of Srilanka. FAO, Rome.
8. Nuyen Hiru Dai va nnk (2002). Reversing Degradation Trends in the Tonkin Gulf Seagrass in the South Vietnam, UNEP Technical Report.
9. Tran Dinh, Nguyen Nhat Thi (1985). Danh muc ca biin Viet Nam. Tuyin tap cdng trinh nghien ciin khoa hgc bien, Vien Nghien ciiu biin Hai Phdng.
10. English S, Wilkinson C, Baker V (eds) (1997). Survey Manual for Tropical Marine Resources, ASEAN-Australian marine science project, Australian Institute of Marine Science, Twonsville.
11. Eschmeyer W N (1998). Catalog of Fishes. Special publication No. 1 of the Center for Biodiversity Research and Information. Califomia Academy of Sciences, vols. 1-3, p. 1-2905
12. Froese R, Pauly D (eds) (2004). FishBase 2004, CD-ROM. ICLARM, LosBanos, Laguna
13. Nakabo T (2002). Fishes of Japan, EngHsh Edition. Tokai University Press.
14. Nelson JS (1994). Fishes of the world, 3"* ed. John Wiley & Sons, Inc, New York 15. Nguyen Hihi Phung, Nguyen Nhat Thi chu bien (1993-1997). Danh muc ca biin
Viet Nam, NXB KH & KT, Ha Ndi
16. Nguyen Nhat Thi (1991). Ca biin Viet Nam. Cd xuomg vinh Bdc Bo. NXB KH &
KT, Ha Noi.
Summary
INITIAL RESULTS OF STUDY ON THE FISH RESOURCES IN THE SEAGRASS BEDS OF CUA DAI (QUANG NAM) AND PHU QUY ISLAND
(BINH THUAN) Nguyen Van Quan
The seagrass beds in the central provinces of Vietnam have been considered as the important sites for both scientific values and livelihood creation of the local communities. However, the information about the living resources of seagrass bed ecosystems seems insufficiently and need more in depth investigations. A field study was carried out in 2006 at selected seagrass beds in Cua Dai (Quang Nam) and Phu Quy Island (Binh Thuan) to assess the status living resources of seagrass beds. Among of the seagrass dwelling groups, fish has been studied as the keystone vertebrate animals found in this important ecosystem.
72 fish species belonged to 55 genera in 41 families were found in the seagrass beds
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of Cua Dai (Quang Nam) and Phu Quy Island (Binh Thuan). Among of them, 6 families contain high in species number such as goat fishes (Mullidae), wrasses (Labridae), rabbits (Siganidae), threadfm breams (Nemipteridae), trevallies (Carangidae), and grouper fishes (Serranidae) have 4 species each, occupy 5.6% of the total recorded species. Other families, following by lizard fishes (Synodontidae) and silverbiddy (Gerreidae) contain 3 species each (4.2%), the rest families have low number of species by 1-2 species. The fish fauna in study area was characterized by less abundance to compare with that of other seagrass beds in the central and south areas of Viet Nam, for example Thuy Trieu lagoon (Nha Trang) and Phu Quoc Island.
The fish resources in the seagrass beds at the study area are represented by the high commercial food fish species: large body size, fast growth rate and high price on the market. They provide the main sources for development of the nearshore fishing activities. However, the natural resources were decreased in recent years found in the aspects of reduction of the fishing yield and percentage of the trash fish increased in each haul. Thus, it may relate to the consequences of the overfishing phenomenon through longterm implementation of the destructive fishing practices.