Hgi nghj Khoa hgc vd Cdng ngh$ bien todn qudc Idn thu V
DA DANG LOAI VATRCLirgnVG CADAY BIEN VIET NAM Vii Vift Ha, Dang Van Thi
Vign Nghien ciiu Hai san. 224 Le Lai, Quan Ngo Quyin, Hai Phong Email: [email protected]
Tom tat:
Da dgng lodi nhom cd ddy & bien Viet Nam dugc phan tich diea tren so lieu tir cdc chuyin diiu tra ngudn lgi bien bdng tdu ddnh lu&i keo giai dogn 1996-2005. Kit qud nghien cihi da thong ke dugc 355 lodi cd ddy diin hinh. thugc 196 gidng nam trong 98 hg thugc 21 bg khdc nhau. Vimg bien 6dng Nam Bg co sd lugng lodi cd ddy phong phii nhdt, viing bien Tdy Nam Bg ngheo nan nhdt vi so lugng hg, giong. loai cd day. Moi viing biin deu co nhimg lodi cd ddy dgc tnmg va cUng co nhiing loai phdn bo rgng bdt ggp a tdt cd cdc viing biin. Da dgng nhdt ve thdnh phdn lodi la bg cd virgc (Perciformes) tiip din la bg cd mil ldm (Scorpaeniformes), bg cd ban (Pleuronectiformes). bg cd chinh (Anguilliformes), bg cd noc (Tetraodontiformes). O cap dg gidng. phong phii nhat la hg cd dii (Sciaenidae) vd hg cd bong (Gobiidae), hg cd chai (Platycephalidae). Ocdp dg Igdi, phong phii nhdt td hg cd lugng (Nemipteridae), tiep den la hg cd li$t (Leiognathidae). hg cd dit (Sciaenidae). Chi sd da dghg sinh hgc (H') udc tinh rieng cho nhom cd day a cdc vung biin vinh Bdc Bg. miin Trung.
Bdng Nam Bg vd Tdy Nam Bg dao dgng trong khodng 0.74 - 1.70; 1,25^
1,81; 1,24-1,57 vd 1,19-1,69. Chi sd H' cUng cho thdy cd sif bien dgng nhdt dinh trong ngi tgi cdc qudn the trong qudn xd cd ddy theo khong gian vd thdi gian. Trie lugng nguon lgi cd ddy d bien Viet Nam (khdng bao gdm trie lugng d ddi dg sdu dudi 20m nu&c) u&c tinh khodng 350 ngdn tan. chiem khodng 30% trong tdng trie lugng ngudn lgi hdi sdn ddnh bdt dugc bdng lu&i keo ddy
DEMERSAL FISH DIVERSITY AND STOCK BIOMASS OF THE VIETNAM SEA
Abstract:
Diversity of demersal fish in the Sea of Vietnam was analysed using the trawl survey data collected in periods from 1996 to 2005. There was 355 demersal fish species identified belongs to 196 genus In 98 families of 21 orders. The Southeast water was the most diversified whereas the Southwest water was observed poorest in term of species composition. Distribution of demersal fish species was area specific. Also, there are some species distributed widely, found in all the sub-area of Vietnam sea. The orders Perciformes, Scorpaeniformes, Pleuronectiformes, Anguilliformes and Tetraodontiformes were the most richness. In term of genus diversity, the
Tieu ban Sinh hgc vd nguon lai sinh vgt Biin
abundance families were Sciaenidae. Gobiidae, and Platycephalidae. The Shannon — Weiner index (H) of the demersal fish community were estimated in the ranges from 0.74 to 1,70; 1.25-1.81; 1.24-1.57 and 1,19- 1.69 for the Tonkin Gulf, Central Area, South East Area and South West Area, respectively. It Is Indicated that the demersal fish community was variable by time and by space. Stock biomass of demersal fish In the Sea of Vietnam (not included biomass of the less than 20m depth strata) was estimated approximately 350 thousand tones, appropriated about 30% of the total trawlable biomass.
1. MO DAU
Bien Vipt Nam ndm ve phia tdy nam Thdi Binh duong, cd thIm lyc dia rpng vdi dja hinh ddy khdc biet giira cac khu vuc, cd noi ddy khd bdng phdng, dp sau khdng Idn nhu vjnh Bdc Bp va Tdy Nam Bp, nhung cung cd nhiing vimg dja hinh ddy phiic tap, dp doc day Idn, do sdu dat tren 4000m nhu vimg bien mien Trung va vung biin xa bd. Dya tren su khac biet ve dieu kien ty nhien, dja hinh dia mao vd ddc diem khi hdu ma bien Viet Nam ' dugc chia thanh 5 vimg chinh: vinh Bdc Bg, vimg bien mien Tnmg, viing bien Ddng Nam Bg, vimg bien Tdy Nam Bp va vimg bien xa bd (Hinh).
Ndm d ddi khi hdu nhiet ddi gid mua, bien Viet Nam la mdt trong nhung khu vyc cd ngudn Igi hdi san phong phii tren the gidi vd cd tinh da dang sinh hpc cao. Theo mot sd cong trinh nghien ciiu da cdng bd, d bien Viet Nam cd 2.458 lodi cd nam trong 206 hg vd nhieu lodi hai sdn khac ngoai cd (Chung & Dinh 2005), trii lugng ngudn lgi hai sdn udc tinh khoang 5 tripu tdn vd khd ndng khai thdc ben viing dat 2,1 tripu tan (San et al. 2009).
Dya tren tap tinh phan bd, ngudn lgi cd bien cd the chia thdnh cdc nhdm chinh, gdm: 1) ca n6i nhd, 2) cd no} Idn, 3) ca day, 4) cd ran san hd. Mdi nhdm cd nhung net dac trung rieng ve khu vyc ciing nhu pham vi phan bd. Vimg bien vinh Bdc B§ vd vimg bien Ddng Tay Nam Bd cd dia hinh tucmg ddi bdn^ phdng, dp sau khdng Idn, do dd su phdn bd cua cac nhdm cd biin tdn tai su pha trpn nhat dinh, ddc biet la giiia nhdm ca ndi nhd, nhdm ca ddy vd nhdm cd ran san hd.
Tdng hgp tai lieu, dii lieu thu dugc tir cdc chuang trinh nghien ciiu khdc nhau trong giai doan 1996-2005, bai vilt nay se cung cap nhiing thdng tin cdn thiet ve hipn trang da dang loai ca day d cac vimg biin Vipt Nam, lam co sd cho cdc nghien ciiu ddnh gid nguon lgi hdi sdn ndi chung vd nhdm cd ddy ndi rieng.
2. TAI LIEU VA PHU'OfNG PHAP NGHIEN ClTU 2.1. Tai lipu
Tai lipu Sli dung trong bdo cdo dugc tdng hgp tir sd lieu dieu tra ngudn lgi hdi sdn bdng tdu danh ludi keo day (ludi keo ddy cd vd ludi keo day tdm) d biin Viet Nam trong giai doan tir nam 1996 din 2005, gdm (Hinh 1):
Hgi nghi Khoa hoc vd Cong nghe bien todn quoc lan thieV
Diiu tra nguin lgi hai san ting day bing tau Ha Long 408 (nam 1996-1997), tau Dang Nam 05 (til nam 2000 din nam 2003) va t4u BV5957 BTS (nam 2004- 2005).
Diiu tra nguin lgi tom bing tau danh luori keo tom o cac nam 2001, 2002 6 vjnh B5c Bg va 2002-2003 a viing biin Dong va Tay Nam B^.
.^
lOi' tC3' 1C4' l o r !0E' 107'
Hinh 1. Tram nghien ciiu nguon lgi hdi sdn tdng day giai dogn 1996 - 2005
Tieu ban Sinh hgc vd nguon lai sinh vdt Biin
Bang 1. Cdc chuyen dieu tra ngudn lgi hdi sdn tdng day da thuc hi$n a bien Viit Nam giai dogn 1996-2005
Nam Vinh Bo
Bac Mien Trung
S o n g Nam Bg va xa bit
Tay Bo
Nam Dieu tra bang tau danh luoi keo ca
1996 1997 2000 2001 2002 2003 2004 2005
2 1 0 2 0 1 1 1
2 1 0 0 0 0 1 1
2 1 2 0 2 1 1 1
0 2 0 2
• 1
1 1 Dieu tra biing tau danh luoi keo tom
2001 2002 2003 Tong
0 2 2 12
0 0 0
s
2 2 0 14
2 2 0 11
Tong cgng 6 3 4 2 4 3 4 4 4 6 2 42 Tong si 42 chuySn dieu tra da dugc th\ic hien a vitng bien Viet Nam, trong do viuig^ bien Dong Nam Bg dugc diiu tra nhiiu nhit (14 chuyen) va viing bien mien Trung dugc dieu tra it nhit (chi voi 5 chuyin), phin Icrn cac chuyen dieu tra sir dung ludi keo day ca (Bang 1).
2.2. Phutmg phap nghien cuu 2.2.1. Pliirangphdp thu thap so lieu
si lieu dugc dugc thu thap bing luoi keo day. Cac chuyin diiu tra nam 1996, tram thu miu dugc bi tri ngau nhien, khong theo luoi chiiu. Cac chuyin diiu tra thiic hien o cac nSm til 2001 din 2005, tram thu mau dugc thiet ke ci dinh nam tren cac mat cit. Khoang each giiia cac tram nghien ciiu va giOa cac mat cat dii voi dieu tia bang tau danh luoi keo day ca la 30 hai ly va doi vdi ludi keo tom la 15 hai ly.
Quy trinh thu mlu va phan tich mau dugc thuc hien theo hudng din ciia FAO (Sparre &
Venema, 1995). Thdi gian keo ludi dao dgng trong khoang 45-60 phiit, tic do keo ludi khoang 4 hai ly dii vdi ludi keo day ca va 3 hai Iy doi vdi ludi keo day tom.
San lugng me ludi dugc phan tich din loai, dua vao cac tai lieu tham khao cua Nguyen HSu Phung (1995; 1997; 1999), Nguyin HCm Phung va Trin Hoai Lan (1994). Cac tai lieu phan loai cua FAO, (Compagno, 1984; Carpenter & Niem, 1999; 1999; 2001) dugc sir d^ing di dii chiiu ten dong vat (Synonym).
2.2.2. Phirong phiip phdn tich so llgu
Toan bg cac chuyen diiu tra 6 cac nam 1996, 2001, 2003,2004 va 2005, gom diiu tra bing ludi keo day ca valudi keo day torn dugc sii dung de phan tich, thong ke danh muc thanh phin loai ca day bat gap bien Viet Nam (tong so 42 chuyen bien).
Hgi nghi Khoa hocvd Cdng nghe bien todn quoc ton thu Y
Thong tin vi chi si da dan^ sinh hgc va nguon lgi nhom ca day dugc mo ta dua tren s6 lieu thu dugc tii cac chuyin dieu tra bing ludi keo day ca.
+ Thanh phin loai
Thanh phin loai dugc phan tich bang phuang phap so sanh hinh thai. De xac dinh cac loai ca day, cac tai lieu chinh dugc su dung la FAO species identification guide fisheiy puipose - The living marine resources of Western Central Pacific (Compagno, 1984;
Carpenter & Niem, 1999; 1999; 2001) va FISHBASE (Froese & Pauly, 2009).
+ Chi so da dang sinh hgc
Chi si da dang sinh hgc (H') dugc tinh theo cong thiic Shannon - Weinerl948):
Trong do H' la chi s6 da dang sinh hgc, s la so loai bit gSp, n, la si lugng ca thi cua loai thii i trong mau va N la ting so ca thi trong mau.
Chi si dong nhit (Eveness, J') dugc tinh theo cong thiic (Pielou 1969)
y dao ddng trong khoang 0-1. J' cdng nhd miic dg bien ddng trong quan xd cang thap vd ngugc lai.
.+ U'ffc tinh tru- luong
Phuang phdp dien tich dugc sii dung de udc tinh trir lugng ngudn Igi cd day theo hudng ddn ciia Pauly (1984), su dung cdng thiic
^ ^ ^ ^ . C P U A ,
B Id trii lugng, S, la dien tich ciia dai dp sau thii i, CPUA^^ Id mat do trung binh cua cac loai ca day tren mdt dan vi dien tich ciia ddi do sdu thii i, q Id he sd ddnh bdt.-He sd ddnh bat q = 0,5 dugc dp dyng ddi vdi ludi gia don ddnh bdt d vung Ddng Nam A (Pauly, 1980).
Mat do phdn bo ciia cdc loai ca day dugc udc tinh theo cdng thiic:
CPUA, =^^^ ~\
cpuA,, = 3 ^ „ ;
Tiiu ban Sinh hgc vd nguon lgi sinh vdt Biin
Trong do CPUAj^ Id mat dg phdn bd (kg/km ) cua cac lodi cd day d ham thii k thugc ddi do sau thii i. Cik, t^, Vik la san lugng, thdi gian va tdc dp keo ludi ciia me ludi d tram thi k d ddi dp sdu thii i, D Id dp md ngang cua mieng ludi trung binh tinh theo ly thuylt thilt kl ludi keo (King, 1995).
3. KET QUA NGHIEN CUtJ 3.1. Da dang thanh phan loai ca day
Tong hgp sp lipu tir 42 chuyen dieu tra ngudn lgi hai sdn tang ddy, da thong ke dugc 355 lodi cd day dien hinh thupc 196 gidng ndm trong 98 hg, 21 bg khdc nhau. Vim^ bien Dong Nam Bd (bao gdm ca vimg bien xa bd) cd sd lugng loai cd ddy phong phii nhdt, vdi 128 lodi thudc 145 gidng ndm hong 87 hg, 21 bp da bdt gap. d vung hiln Tay Nam Bg chi bdt gap 134 loai cd day thupc 81 gidng, 52 hg, 14 bp. Sd hg gidng lodi cd ddy bdt gap d viing biin vinh Bdc Bp vd viing bien mien Trung chenh Ipch nhau nhieu (Bang 2).
Bdng 2. Sd lugrng hg, gidng. lodi cd ddy bdt gap a cdc vitng bien Viet Nam Viing bien
Vjnh BSc Bo Mien Trung Dong Nam B6 va xa bd Tay Nam Bo Toan viing
Bo 14 17 21 14 21
Ho 67 77 87 52 98
Giong 115 121 145 81 196
Loai 206 196 248 134 355
Trong cac bg ca biin da bit gap thi bg ca Vugc (Perciformes) da dang nhSt ve thanh phin loai ca day, vdi 31 hp (chiim 31,6%), 72 giing (chiim 36,7%) va 156 loai (chiim 43,9% ting si loai ca day). Ngoai ra, bg ca mu lan (Scorpaeniformes), bg ca bon (Pleuronectiformes), bg ca chinh (Anguilliformes), bg ca noc (Tetraodontiformes) la nhiing bg CO si lugng hg/giing/loai phong phii so vdi cac bg khac. Cd 5 b6 chi bat gSp mgt hg, mgt giing, mgt loai la bg ca mang sOa (Gonorynchiformes), bg ca mat trang (Lampriformes), b6 ca chinh moruy (Ophidiiformes), bg Squatiniformes va bg Zeiformes (Bang 3).
Thanh phin loai ca day d cac vimg biin khac nhau ciing cd nhiing net dac trung rien|.
6 vinh Bic Bg co 37 loai dac trung, khong thiy bit gap d cac vimg biin khac. 6 vimg bien mien Trung co 32 loai, viing biin Dong Nam Bg c6 54 loai va viing biin Tay Nam Bg chi CO CO 8 loai d|c trung. Ben canh dd, da xac dinh dugc 78 loai ca day co pham vi phan bo rgng khip, bit gap d tat ca cac vimg biin, tii vinh Bic Bo tdi vimg bien Tay Nam Bg (Phu Ivc).
Hgi nghj Khoa hgc vd Cdng nghj bJen todn qudc Idn thu V
Bdng 3. Cdu true thdnh phdn lodi cd ddy a biin Vi0t Nam dira tren kit qud dieu tra bdng luai keo day giai dogn 1996-2005
Ten bo
AnguiUiformes Aulopiformes Carcharhinifonnes Gasterosteiformcs Gonorynchiformes Hcterodontiformes Lampriformes Lophii formes Ophidiiformes Oreciolobiformes Osmcriformcs Perciformes Pleuronectiformes Raj 1 formes Scorpaeniformes Siluriforines Squatiniformes Syngnathi formes Tetraodontiformes To rpcdini formes Zeiformes
T O N G
Ten tieng Vi?t
B9 ca chinh Bp ca chao Bo ca nham Bp ca gai Bp ca mang siia
Bp ca m^t trang Bp ca luai dong Bp ca chinh moruy Bp ca nham rau
Bp ca vupc Bp ca bon Bp ca (luoi B Q ca mil lan Bp ca nheo
Bp ca chia voi Bo ca noc Bp ca duoi dien
si
l>9 6
31
H
98 T i l l
(%)
6,1 3,1 5,1 1.0 1,0 1,0 1,0 4,1 1,0 2,0 1,0 31,6 8,2 6,1 11.2 3,1 1,0 4,1 6,1 1,0 1,0 100,0
So giong 14 4 7 1 1 1 1 4 1 2 I 72 21 9 27 3 1 5 18 2 1 196
Tilf
(%)
7,1 2,0 3,6 0,5 0,5 0,5 0,5 2,0 0,5 1,0 0,5 36.7 10,7 4,6 13,8 1.5 0,5 2,6 9,2 1,0 0,5 100,0
si loii 17 10 7 2 1 2 1 4 I 3 2 156 41 22 39 7 1 5 30 3 1 355
Tilf
(%)
4,8 2.8 2.0 0,6 0,3 0,6 0,3 1,1 0,3 0,8 0,6 43.9 11,5 6,2 11,0 2.0 0,3 1,4 8,5 0,8 0,3 100,0
O cap dp giong, xet chung tren todn viing bien thi hp cd du (Sciaenidae), hp cd bdng (Gobiidae), hg Platycephalidae phong phii nhdt, moi hp da bdt gdp 8 gidng khdc nhau. Co 4 hp bat gap 6 gidng la hp cd noc (Tetraodontidae), hp cd mu (Serranidae), hp ca bon (Bothidae). Cd 3 hp bat gap 5 gidng, 3 hp bdt gdp 4 gidng, 7 hp bat gap 3 gidng, 21 hp bdt gap 2 gidng vd 56 hp chi bdt gap 1 gidng (Phu luc).
6 cap dp lodi, hp ca luang (Nemipteridae) phong phu nhdt vdi 18 loai da duac xdc dinh trong cdc chuyen dieu tra ngudn lai. Tiep theo la hp ca liet (Leiognathidae) vdi 16 loai, ho
Tieu ban Sinh hgc vd ngudn lgi sinh vgt Biin
ca mu (Serranidae) vdi 14 loai va hp ca ndc (Tetraodontidae) vdi 13 lodi, hp cd du (Sciaenidae) vdi 12 lodi. Hp cd bdng (Gobiidae) vd hp ca ban (Cynoglossidae) d^u bit gap 11 lodi. Cd 32 hp chi bdt gap mdt lodi (Phu luc).
Gidng cd luong (Nemipterus) bdt gdp sd loai nhieu nhdt, vdi 14 loai, tiep den la gidng ca liet (Leiognathus) vdi 12 loai. Cdc gidng ed dudi (Dasyatis), ca song (Epinephelus). ca ban (Cynoglossus), cd phen (Upeneus) vd ca ndc (Lagocephalus) Id nhiing gi5ng cd thdnh phdn loai phong phu. Ket qua khdo sdt giai doan 1996-2005 ciing da thdng ke dupe 129 giong cd ddy chi bdt gap mdt loai duy nhat.
3.2. Chi so da dgng sinh hgc
Chi sd da dang sinh hpc Shannon Weiner (H') tinh rieng cho nhdm ca ddy theo cdc ddi dp sau khac nhau vd cho tirng vung bien duac trinh bdy d Bdng 1,2,3,4. C) chuyen dieu tra trong mua gid Tdy Nam nam 1996, cdc tram nghiSn cihi dupe thu mdu ngdu nhien, cdc chuyen dieu tra cdn lai tram thu mau duac thiet ke co dinh, dd la ca sd de so sdnh ket qud nghien cuu giQa cac khoang thdi gian khdc nhau.
+ Vung bien vinh Bdc Bg:
Ket qua dilu tra cho thdy chi sd da dang sinh hpc cua nhdm cd ddy dao ddng trong khodng 0,69 den 1,68. Chuyen dieu tra d miia gid Tdy Nam nam 1996 do he thdng tram nghien cuu dupe thiet ke khdc cdc chuyen dieu tra cdn lai do vdy khong the so sdnh.
Chi sd da dang sinh hpc (H') khac nhau giua cac chuyen dieu tra cho thdy cd su bien dgng nhdt dinh trong qudn thi cdc loai cd day. Chi sd da d?ng sinh hpc cao chiing td cdc loai cd ddy phdn bd trong vung biin cd tinh tuong ddng vl sd lugng cd the trong qudn thi.
Chi s6 da dang sinh hpc thdp biiu thj trong nhdm cd day cd mot sd lodi chilm uu the ve sd lugng so vdi cdc lodi cdn lai.
CJ chuyin dilu tra nam 2003 chi s6 da dang sinh hoc ciia nhdm cd ddy thdp nhdt. Tinh chung cho todn viing biin, chi so H'=0,69. 6 hdu het cdc chuyin dilu tra, chi sd da dang sinh hgc thdp nhdt d ddi dp sdu 20-30m nude yd cao nhdt d dai dp sau dudi 20m. Tuy nhien, kit qua dilu tra nam 2005 cho thay, chi sd da dang sinh hpc d ddi dp sdu dudi 20m nude da gidm xudng thdp nhdt so vdi d cdc ddi dp sau khdc.
Cdc chuyin dilu tra d nam 2001 vd 2005, chi sd da d?ng sinh hpc cua nhdm cd ddy kha dong deu, dao dpng trong khoang 1,16 - 1,36 d ndm 2001 va 1,56-1,88 d ndm 2005 (Bang 4), dilu dd cho thdy tinh da dang sinh hpc ciia nhdm cd ddy trong cac thdi diem nay cd sir hrong ddng d cdc dai dp sau khdc nhau.
Kit qud phan tich chi so da dang sinh hpc (H') d tirng tram nghien cuu cho thdy vimg Men H? Long - Long Chau, vimg bien Nghe An - Hd Tinh vd khu vuc phia Nam ddo Bach Long Vy la nhiing khu vuc cd tinh da d?ng sinh hpc cao ban so vdi nhiing khu v\ic khac.
Hdi nghj Khoa hgc vd Cdng nghi bien todn qudc idn thu V
Bdng 4. Chi sd da dgng sinh hgc ciia nhdm cd day ay\nh Bdc Bg. uac tinh cho tung ddi do sdu vd cho todn viing bien. dua tren kit qua diiu tra bdng tdu ddnh luai keo day
Chuyen dieu tra T6/1996 T12/1996 T6/2001 Tl 1/2001 T6/2003 T6/2004 Tt/2005
Dai d3 sSu (m)
<20
1,32 0,95 0,76 1,40 1,56
20-30
0,49 1,16 0,97 0,22 0,80 1,57
30-50 0,34 0,94 1,26 1,28 0,98 1,08 1,88
50-100 0,86 1,06 1,36 1,04 0,81 0,76 1,70
Todn viing bien 0,79 0,95 1,29 1,12 0,74 0,98 1,70 + Viing bien mien Trung:
Chi sd da d^ng sinh hpc (H') dao dpng trong khoang 1,2 - 1,8, cao nhat d chuyen dieu tra trong mua gid Tay Nam 2005 va thdp nhdt d chuyen dieu tra trong mua gid Tay Nam nam 1996. Su bien dpng chi sd da dang sinh hpc vdi bien dp Idn chung td thdnh phdn loai vd sd lupng loai chiem uu the hong nhdm cd day cd su thay ddi theo thdi gian. Chi so H' tang len d ndm 2005 chung td sd lugng lodi cd ddy chiem iru the da tang len so vdi cdc thdi diem dieu tra trude.
Giiia cdc ddi dp sdu, chi sd da dang sinh hpc khdng khac nhau nhilu chung td thanh phdn lodi vd cdc lodi chiem uu the d cac ddi dp sdu khdc nhau cd tinh tuang ddng. Ddi dp sau 100-200 m nude cd tinh da dgng sinh hpc cao nhdt, nguac lai ddi dp sdu 20-30 m nude cd tinh da dang sinh hpc thap nhat.
Bdng 5. Chi sd da dgng sinh hgc ciia nhdm cd day a viing bien mien Trung, uac tinh cho tirng ddi do sdu vd cho todn viing bien. dua trin kit qud dieu tra bdng tdu ddnh lir&i
keo ddy
Chuyen dieu tra T6/1996 T12/1996 T6/2004 T6/2005
20-30
0,12 1,86
30-50
1,35 0,95 1,56
Dai d9 sau 50-100
1,14 1,50 1,43 1,90
(m) 100-200
1,45
1,59 1,88
>-200 1,08
Toan viing bien 1,25 1,49 1,32 1,81
Tiiu ban Sinh hgc va nguon lgi sinh vgt Bien
+ Vimg bien Ddng Nam Bd vd xa bd
Chi sd da dang sinh hpc (H') d vimg bien Ddng Nam Bp va xa bd dugc udc tinb dao dgng hong khoang 1,24 - 1,57. Chi sd da dang sinh hpc (H') cao nhdt udc tinh dupe d chuyen dieu tra d mua gid Ddng Bac nam 2002 (H'=l,57), thdp nhdt d cac chuyen dilu tra nam 1996 (H'=l,24 d miia gid Tdy Nam vd 1,25 d miia gid Ddng Bdc). Cac chuyin dilu tra khac chi sd da dgng sinh hpc dao dpng xung quanh gia tri 1,3-1,4. Nhu vgy, xet tren todn viing biin thi tinh da dang sinh hpc ddi vdi nhdm cd day d vimg biin Ddng Nam Bg vd xa bd co si^ thay doi khdng nhieu theo chudi thdi gian.
Xet rieng doi vdi tirng ddi dp sdu, su bien ddi ciia chi sd da dang sinh hpc diln ra theo hudng gidng nhau. Chi sd da dang sinh hpc cao d cdc ndm 2002-2003 vd thdp d cac nam c6nlai(Bang6).
Bdng 6. Chi sd da dgng sinh hgc cua nhdm cd ddy a viing biin Ddng Nam Bg, uac tinh cho tirng ddi dg sdu vd cho todn viing biin, dya trin kit qud dieu tra bdng tdu ddnh luai
keo ddy Chuyen dieu tra
T6/1996 T12/1996 T6/2000 T12/2000 T6/2002 Tl 2/2002 T12/2003 T6/2004 T6/200S
Dai d9 sau (m) 20-30
1,31 1,52 1,30 1,70 1,80 1,74 1,20 1,70
30-50
1,32 1,48 1,38 1,35 1,61 1,57 1,21 1,36
50-100 1,09 1,25 1,44 1,44 1,51 1,39 1,21 1,29 1,27
100-200 1,38 1,14 1,43 1,15 1,47 1,42 1,54 1,73 1,54
Toan vung bien
1,24 1,25 1,46 1,37 1,44 1,57 1,43 1,31 1,39
+ Viing bien Tay Nam Bg
Chi sd da dang sinh hgc cua nhdm ca ddy d vung bien Tay Nam Bg udc tinb dao ddng trong khodng 1,34 - 1,69 vd cd su biin dpng vdi bien dp khd Idn giiia. miia Tay Nam va miia gid Dpng Bdc. Su bien ddng chi so da dang smh hpc giiia hai mua gid cho thdy thanh phan lodi cd day cung nhu cac loai ca ddy chiem mi the d vimg bien cd sy bien ddi khdc nhau va cd th6 chju dnh hudng cua su thay ddi cua gid miia.
Hgi nghj Khoa hgc vd Cdng nghj bien todn gudc Idn thu V
Bdng 7. Chi sd da dgng sinh hgc cua nhom cd ddy a viing bien Tdy Nam Bd. uac tinh cho timg ddi dg sdu vd cho todn ivng bien. dua tren kit qua dieu tra bdng tdu ddnh ludi keo
ddy Chuyen dieu tra
T6/2000 T12/2000 T6/2002 T12/2002 T12/2003 T6/2004 T6/2005
20-30 2,00 1,19 1,82 1,59 1,55 1,37 1,67
Dai d9 sau (m) 30-50
1,74 1,12 1,27 1,65 1,15 1,45 2,03
50-100 1,30 1,28 1,63 1,75 1,42 2,08 0,81
Toan viing bien
1,69 1,19 1,53 1,65 1,34 1,53 1,67
Giua cdc ddi dp sdu, chi sd da dang sinh hpc chng cd su bien dpng nhat dinh. Cd chuyen dieu ha, vung nude ven bd dupe xdc djnh la khu vuc cd chi. sd da dgng smh hpc cao hem cdc vung cdn lgi, tuy nhien ciing cd mpt sd thdi diem khao sat khac vimg nude ven bd la noi cd chi sd da dgng sinh hpc thap hon (Bang 7).
3.3.Trir luffng nguon lgi
Trir lupng ngudn lgi ca ddy d bien Viet Nam dugc trinh bay d Bang 8. Do thilu dii lieu dieu tra d vung bien ven bd tir 20m nude trd vdo d vimg biin miln Trung, Ddng va lay Nam Bd nen trii lugng ngudn lgi chua dugc danh gia ddy du. Cac nam khac nhau phgm vi dieu ha ciing khdc nhau, chi cd ndm 2004 va 2005 dieu tra n ^ d n lgi cd day mdi dugc thuc hien ddng thdi tren todn vung bien. Ket qud dieu tra cho thdy, trii lugng ca day cd su hien dgng rat Idn. Nam 2004, trii lugng cd ddy udc tinh khoang 400 ngan tin, trong do dong gdp phan Idn vao tru lupng ngxidn lgi la vim^ bien mien Trung (khoang 165 ngdn tdn) va vimg bien Ddng Nam Bd (khoang 131 ngan tan. Trii luong ngudn lgi d vimg biin vinh Bac Bd vd viing bien Tay Nam Bd tuong duong nhau, udc tinh khoang 57 ngdn tin d vinh Bac Bd vd 54 ngdn tin d viing biin Tdy Nam Bp.
Ket qud dieu tra ndm 2005, hir lugng ngudn lgi ca day udc tinh khodng 288 ngan tdn, gidm khoang 30% so vdi trii lugng ngudn lgi d ndm 2004. Su suy gidm nguon led chii yeu xay ra d vung bien Ddng Nam Bp (giam khoang 41%). CJ vung bien mien Trung va viing bien mien Tdy Nam Bd su suy giam ngudn lgi cd day d muc tuong duong nhau (viing bien Mien Trung gidm khoang 28,1%; vimg biin Tdy Nam Bd gidm khoang 30,6%). Tinh chung cho ca giai doan, trir lugng ngudn lgi ca ddy trung binh d biin Viet Nam khoang 348 ngdn tan.
Tiiu ban Sinh hgc vd ngudn lai sinh vdt Biin
BdngS. Tru lugng ngudn lgi cd ddy (tdn) d cdc viing bien Vi^t Nam dua trin kit qud diiu tra bang tdu ddnh lu&i keo ddy. Cdc chuyin dieu tra du(?c thuc hien a miia gid Tdy Nam
Nam dieu tra 2000 2001 2002 2003 2004 2005 Trung binh
VBB
-
29.247
-
34.313 57.051 55.302 56177
M T
- -
165.106 118.654 141880
DNB 109.430
-
83.901
-
131.554 , 77.329 104441
TNB 42.456
-
43.940
-
54.182 37.615 45899
Toan vung bien
- - -
407.893 288.900 348.396 Ghi chii: (-): khong dieu tra
Kit qua udc tinh trii lugng nguon Ipi ca va hdi sdn ngoai cd ddnh dugc bdng ludi keo ddy ciia Ddo Manh Son vd nnk (2009) cho thdy, tru lupng ngudn lgi hdi sdn tang ddy khodng 1,1 trieu tdn tuong ung vdi khd nang khai thac khodng 587 ngdn tdn Trong nghien cuu ndy, trii lugng cd day dugc udc tinh rieng cho cdc loai cd ddy dien hinh, todn bd cdc loai khac ddnh bat dugc bang ludi keo ddy nhung khdng thugc nhdm ca day dien hinh deu khong sir dung dl tinb toan Mat khdc, pham vi nghien cuu ciia Dao Manh Son vd nnk cd du dodn trii lupng ngudn lgi d viing bien dudi 20m nude khdng cd dii lieu dieu tra Trong n^ien cuu nay, neu trii lupng ngudn lgi cd ddy d vimg bien ven bd dupe dieu tra, danh gid day du thi trii lugng nguon lgi cd day cd the tang len ddng ke Nhu vdy, trii lupng ngudn lgi cd day diln hinh chi chilm ti 1? khodng 30% trong tdng trii lugng ngudn lgi ddnh dugc bdng ludi keo ddy Dilu nay cd thi giai thich rang, trong san lupng ddnh bat cua ludi keo day, ngoai cac lodi cd day diln hinh thi rat nhieu loai hdi san thudc cdc nhdm khdc ciing bi bdt nhu nhom cd ran, nhdm cd ndi, nhdm gidp xdc, nhom chdn ddu Cac nhdm ndy cd the song d ting ddy trong mdt giai dogn nhdt dinh trong vdng ddi hoac chi kilm dn d tang day Viec ddnh gid trii lugng ngudn lgi ca day can tdch bach giiia cd day thuc thu va cdc lodi, nhom lodi khdc
4. KET LUAN
Da thdng ke dugc 355 lodi cd ddy diln hinh thudc 196 gidng nam trong 98 hp, 21 bd khac nhau, viing biin Ddng Nam Bp cd sd lugng loai ca ddy phong phu nhat, vdi 128 lodi thupc 145 gidng ndm trong 87 hp; vimg blln Tdy Nam Bd chi bat gap 134 loai ca day thugc 81 gidng, 52 hp.
Bg ca Vugc (Perciformes) da dgng nhit vl thanh phan loai cd day. Bd cd mu lan (Scorpaeniformes), bd cd bon (Pleuronechformes), bd ca chinh (Anguilliformes), bd cd noc (Tetraodontiformes) la nhiing bg cd sd lugng hp/gidng/loai phong phii so vdi cac bg khac.
C6 5 bp chi bdt gap mot hp, mpt giong, mdt loai.
Hdi nghj Khoa hgc vd Cdng nghj bien todn qudc Idn thir V
Hg cd dii (Sciaenidae), hg ca bdng (Gobiidae) vd hg Platycephalidae phong phu nhdt vl sd lupng gidng, hp ca lugng (Nemipteridae), hg ca liet (Leiognathidae) va hg cd mii (Serranidae) phong phii nhit vl sd lugng lodi.
Thanh phin lodi cd day d cac vung bien khdc nhau ciing cd nhihig net ddc trung rieng.
6 vinh Bdc Bp cd 37 loai dac trung, khdng thdy bdt gap d cac vung bien khac. 6 vimg bien miln Trung cd 32 lodi, vung bien Ddng Nam Bp cd 54 loal va vung biin Tay Nam Bg chi cd cd 8 lodi ddc trung. Ben canh dd, da xac dinh dugc 78 loai ca day cd phgm vi phdn b6 rgng khdp, bdt gap d tit ca cdc viing bien, tir vinh Bdc Bp tdi vung bien Tdy Nam Bg.
Chi sd da dgng sinh hpc H'd cac viing bien cd sir bien dpng theo khdng gian va thdi , gian, cho thay su biin ddi trong npi tgi cdc qudn thi trong quin xa ca day. CJ vjnh Bdc Bp,
vimg biin dudi 20m nude cd tinh da dang sinh hpc cao nhdt. 6 vimg bien mien Trung, tinh da dang cao nhdt quan sdt dugc d ddi dp sau 100-200m nude. CJ vimg bien Ddng Nam Bp, tinh da dgng sinh hgc ciia cdc ddi dp sdu tuong duong nhau va vtmg biin Tdy Nam Bp, tinh da dang sinh hpc cao nhat thudc ve ddi do sau 20-30m nude.
Trii lugng ngudn Igi cd ddy d bien Vi?t Nam (khdng bao gdm vimg bien dudi 20m nude) nam 2004 udc tinh khodng 400 ngdn tan. Ndm 2005, ket qud dieu tra cho thdy trir lugng ngudn lgi cd ddy dd gidm khodng 30% so vdi nam 2004, udc tinh khodng 288 ngan tan. Trii lugng cd ddy se cao ban neu dugc udc tinh ddy dii cho ca vung bien ven bd.
TAI LI]pU THAM KHAO
1. Biii Dinh Chung & Trdn Dinh (2005). "Danh myc ban ddu cac loai cd bien Vi?t Nam."
Tuyen tap cdc cdng trinh nghien cuu nghe cd bien Tap 3: 200-210.
2. Dao Mgnh Son, Vii Viet Ha, Dang Vdn Thi, Nguyen Viet NghTa, Bach Van Hgnh &
Mai Cdng Nhudn (2009). Ngudn lgi hdi sdn biin Viet Nam giai dogn 2000-2005.
Tuyen tap Hpi nghi Khoa hpc toan qudc ve sinh hpc bien vd phdt trien ben vung, Nha xudt ban Khoa hpc tu nhien vd Cdng nghf.
3. Nguyin Hiiu Phung (1995). Danh myc cd bien Vi?t Nam, tap 3. Bg cd vupc (Perciformes), bp phu cd vugc (Percoidei) vd bp phy cd ep (Echeneoidei). Ha Ngi, Nha xudt bdn Khoa hpc vd Ky thuat.
4. Nguyen Hiiu Phyng (1997). Danh m\ic cd biin Viet Nam, Tap 4: Bp cd Vugc (Perciformes), tiep tir bd phu cd bdng chai (Labridae) den bp phy cd chim trdng (Stromateoidei), Nhd xuit ban Khoa hpc vd Ky thudt Ha Npi.
5. Nguyen Hiiu Phyng (1999). Danh myc ca biin Vigt Nam, tap 5. Bg ca mil lan (Scorpaeniformes), bg cd ban (Pleuronechformes), bp ca ndc (Tetraodontiformes), bp cd nhdi (Lophiiformes), bp cd cdc (Bahachoidiformes) vd bd ca rdng (Pegasifonnes).
Ha Npi, Nha xudt bdn Khoa hpc va Ky thudt.
6. Nguyin Hiiu Phung & Trin Hoai Lan (1994). Danh muc ca biin Vigt Nam, Tgp 1:
Ldp cd luang tiem (Amphioxi) vd ldp ca sun (Chondrichthyes), Nha xudt bdn Khoa hgc va Ky thugt Hd Ndi.
Tiiu ban Sinh hgc vd ngudn lgi sinh vdt Biin
7. Caipenter K. E & Niem V. H, Eds. (1999). FAO species identificahon guide for fisheries purpose. The living marine resources of the Western Central Pacific. Bony fish part 2 (Mugilidae to Carangidae). ROME, FAO.
8. Carpenter K.E & Niem V.H, Eds. (1999). FAO species identification guide for fishery purposes. The living marine resources of theWestem Central Pacific
9. Rome, FAO. 1999. pp. 1397-2068
10. Carpenter K.E & Niem V.H, Eds. (2001). FAO species identification guide for fishery purposes. The living marine resources of theWestem Central Pacific. Rome, FAO.
^ 1 . Compagno L.LV. (1984). FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of sharks species known to date.,ROME, FAO.
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www.fishbase.org. version (07/2009).."
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Rome, FAO.
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Bell System Technical Journal 21: 379-423 and 623-656.
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