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Tap chi Khoa hoc va Cong nghe biin T9 (2009) So Tr - NGUON LOI THAN MEM HAI MANH VO VUNG BIEN BINH THUAN TRONG MOI QUAN HE VOfI HIEN TlTONG N U c TROI VO SI TUAN, HlTA THAI TUYEN Tom tdt: Kit qud nghien cicu cua nhieu de tdi khdc trang thai ky 1990 - 2005 cha phep khdng dinh viing bien ven bd Binh Thudn la viing phdn bo vai mat cao cua nhiiu loai thdn mem hai mdnh sdng a viing dual trieu, diin hinh Id: Diep qugt (Chlamys nobilis), Sd ldng (Anadara antiquata), Ddm ndu (Modiolus phllippinarum), Nghiu lua (Paphia undulata) vd Bdn mai (Pinna sp.) Sic giau cd vdt chdt him ca ddng trdi mgnh vd hiiu img true tlip su phong phii thirc vdt phii du (vd cd thi cd qud trtnh chuyin ddi vdt chdt sau thai ky trdi mgnh) Id nhiing yiu to thudn lai cha su phdt trien thudn lai cita cdc dong vgt thdn mim hai mdnh an loc ndy Tiiy thudc vao dgc tinh sinh thdi qudn thi md muc dd lien quan den hieu ung sinh thdi cua viing trdi mgnh cd thi khdc giica cdc lodl Diep qugt la loai phu thudc nhiiu nhdt, sau Id Ddm ndu Sd long vd Nghiu lua cd mdi quan hi din cdc yiu td liin quan nuac troi vd vdt chdt lua dia tdi mua mua Cd thi cho rdng su thay ddi cuang dd vd vi tri tdm ciia viing trdi mgnh cd the chi phdi cdc qud trinh sinh hoc vd tic dd gdy nin su bien ddng sinh khdi ciia cdc qudn the thdn mim hai mdnh vd vung biin Binh Thudn I MOf DAU Binh Thuan la mdt tinh duyen hai Nam Trang bg cd chieu dai bd bien 192 km, dien tich mat nudc bien khoang 52.000 km^ Viing bien dugc coi la ngu tradng ldn cho nghe khai thac thuy san Dac biet, viing bien ven bd Binh Thuan la noi sinh s6ng ciia mgt s6 loai than mem hai manh vo co gia tri'kinh te cao nhu diep quat, sd ldng, ban mai, ngheu lua San lugng khai thac cac d6i tugng dat tit 20.000 - 40.000 tan m6i nam, gdp phan lam tang gia tri san xuat thuy san ciia tinh, giai quyet cdng an viec lam cho mgt so lugng ldn ngu dan ven bien, gdp phan tang thu nhap cho nhan dan va tang thu ngan sach cho dia phuang Cac nghien cim chung ve ngudn lgi than mem (Vd ST Tuan, 1997b; Nguyen Hilu Phung va cs, 2001) cho rang viing bien Binh Thuan la noi dac biet phong phii ciia than mem hai manh vd sdng d vimg dudi trieu De phuc vu cho quan ly khai thac ben vung ngudn lgi, nhieu de tai khoa hgc cap tinh da dugc tiln hanh va cung cip nhilu dan lieu vl phan bl, sinh san, sinh tradng va biln dgng nguIn lgi cdng nhu dl xuit cac giai phap khai thac hgp ly Tuy nhien, viec he thdng hda tu lieu nhim nit nhiing nhan dinh mang tinh 63 khoa hgc ve quan he giiia dieu kien mdi tradng va tinh dgc dao cua nguIn lgi than mem hai manh vd chi mdi dugc tien hanh gin day Mdt dilu cin phai luu y la viing giau co nguon lgi nam d khu vuc chiu anh hudng manh ciia hien tugng nudc trdi miia gid tay-nam Viec nghien ciiu quan he giiia dieu kien moi tradng ndi chung va anh hudng ciia hien tugng nudc trdi ndi rieng vdi ngudn lgi than mem chi mdi quan tam budc dau d6i vdi vai ddi tugng nhu Diep quat va Sd long (Vd ST Tuan, 1997a; Biii Hdng Long & Vd ST Tuin, 1997) H PHI/ONG PHAP NGHIEN CLTU Tong quan tai lieu thv cap Trong giai doan 1991 - 1994 mdt sd de tai nghien ciiu lien quan den ngu6n lgi than mim hai manh vd da dugc tien hanh d Binh Thuan, bao gdm "Nghien cim ve sinh hgc, kha nang khai thac, di gidng va bien phap sii dung ngudn lgi Diep Chlamys nobilis a vimg bien Thuan Hai", "Nghien cim mdt sd dac diem sinh hgc ciia Dom nau Modiolus philippinarum", "Dieu tra ngudn lgi va dac tinh sinh hgc cua Sd long Anadara antiquata" Trong khudn khd de tai cap Nha nudc KT 0305 PGS TS Vd Van Lanh lam chu nhiem (Vd Van Lanh, 1995), tac ddng sinh thai cua dong trdi manh ddi vdi nguIn lgi than mim hai manh vd d tinh Binh Thuan ciing da budc dau dugc xem xet Ket qua da cdng b6 lien quan den quan he ciia sinh vat ngudn lgi vdi dieu kien mdi tradng (Vd ST Tuin, 1997a, b; Biii Hdng Long & Vd ST Tuin, 1997; Pham Van Thom & Vd ST Tuin, 1998) khuon khd cac de tai ndi tren dugc sii dung cho viec he thdng hda tu lieu Nghien ciru bo sung Trong giai doan 2002 - 2004, de tai ""Nghien ciiu cac qui luat sinh hgc, phan b6, di chuyen va du bao bien dgng ngu6n lgi cua mgt s6 loai than mem hai manh vd tai virng bien Binh Thuan" da cho phep tien hanh khao sat ddng thdi tat ca cac ngudn Igi dgng vat than mem hai manh vd quan trgng, bao gdm Diep quat {Chlamys nobilis) So 16ng {Anadara antiquata), Ddm nau {Modiolus phllippinarum), Ngheu lua {Paphia undulata) va Ban mai {Pinna sp.) D I tai da tiln hanh ba chuyen khao sat vao cac thang va 10/ 2003 va thang 5/ 2004 Mau smh hgc va mdi tradng dugc thu thap tren 21 tram tit sau 25 m trd vao bd Ciing khudn khd de tai, cac th6ng tin v l biln dgng san lugng khai thac dugc thu thap qua tham vin vdi cac co quan chite nang ciia dia phuong va cdng ding Cac ket qua nghien cuu lien quan den phan bd, sinh trudng va mdi trudng song cua cac loai noi tren khudn kh6 de tai dugc phan tich nham tim hieu m6i quan he giiia sinh hgc ngudn lgi vdi cac dac tnmg mdi tradng vimg bien, chii trgng din hien tugng 64 nude trdi Ngoai ra, cac tac gia da tim hilu phan b l ciia cac loai tren nhiing khao sat thuoc cac dl tai khae thdi gian gin day III KET QUA VA THAO LUAN Thanh phan, phan bl Tdng hpp cac ket qua nghien cim cho phep khang dinh viing bien ven bd Binh Thuan la vung phan bd vdi mat dp eao eiia nhieu loai than mem hai manh s6ng d vimg dudi trieu Cac loai co y nghTa quan trpng ve san lugng va gia tri bao gdm: Diep quat {Chlamys nobilis), Sd 16ng {Anadara antiquata), Dom nau {Modiolus phllippinarum), Ngheu lua {Paphia undulata) va Ban mai {Pinna sp.) Dieu can luu y tat ca cac loai deu la sinh vat s6ng vui hoac bam tren nen day d vimg dudi trieu va co tap tinh an Igc thuc vat phii du d tang day va vat chat hUu co tram tich hoac d tang sat day Ket qua nghien cim ciia de tai KT 0308 ve cac loai dac san ciia viing bien ven bd Viet Nam da nhan dinh rang cac dgng vat than mem hai manh dac biet phong phu d viing bien tir Binh Thuan den Vdng Tau cae loai dgng vat than mem hai manh s6ng d vimg trieu lai phan bd tap trung d vimg ven bien mien Bac va Nam bd (Nguyen Hiru Phung & cs, 2001) Nghien ciiu cua Pham Van Thom & Vo ST Tuan (1998) da budc dau khang dinh ty le C/N (hiiu co) tram tfch la yeu td tao nen su khac biet cua viing bien ven bd Binh Thuan Ty le C/N trung binh nghien ciiu d Binh Thuan vao nam 1993 cd gia tri xap xi 11, phan anh mdt hdn hgp ciia thuc vat phii du (cd ti sd C/N vao khoang 7) va vat chat hiru co co ngudn gdc luc nguyen (ti so C/N rat ldn) Dac diem tram tich cua viing bien Binh Thuan khac biet vdi tram tich cua vimg cita s6ng Me K6ng noi uu the ciia vat chat CO ngudn gdc luc nguyen (ti s6 C/N eiia 33 mau phan tich d Tra Vinh len den 22,31 s6 lieu chua c6ng b6 ciia de tai KT 0308) va phong phii cac than mem hai manh vimg trieu nhu Ngheu {Meretrix lyrata) va Sd huyet {Anadara granosa) Vdi phan tich tren cd the cho rang phan b6 ciia eac than mem hai manh vo d vimg bien Binh Thuan lien quan chat che den ngudn thiic an la thuc vat phii du ma su phong phii ciia chiing lien quan chat che den hieu ilng sinh thai ciia hien tugng nudc tr6i Khao sat ve thuc vat phu du khu6n khd de tai KT 0305 (Nguyen Nggc Lam 1997), da ket luan sinh lugng ciia thuc vat phii du d viing tam nudc trdi tuong ddi thap, nhung kha cao d vimg phia Nam tam nudc trdi, vdi dinh cao nhat vao thang 7, trimg vdi thdi ky cd dong tr6i manh nhat So phan bd xay dung bdi nghien ciiu tren cho thay vimg ven bien Binh Thuan la khu vuc cd mat cua thuc vat phu du rat cao, dac biet viing ven biln huyen Tuy Phong cd gia tri mat Ien tren 10x10^ tl bao/m^ hoac thi tich 30ml/ml Nhu vay, co thi 65 cho ring sinh kh6i thuc vat phii du tao tir hieu ling nudc trdi la mdt yeu to quan trgng dii vdi su giau cd cua ngu6n lgi than mem mem hai manh vo d viing bien Binh Thuan Cac nghien cim nhilu nam qua cho phep xay dung so d6 phan b6 chi tiet ciia cac loai nhu dugc thi hien tren cac hinh 1, 2, 3, va sau day Cac so khang dinh tinh phan bl tap trang ciia cac loai d vimg bien ven bd Binh Thuan d6ng thdi cdng chi dac dilm rieng vl phan bd cua cac loai su khac ve dac diem sinh thai ciia sinh vat, va tinh khdng ddng nhit va biln dgng vl dieu kien mdi tradng Quan he giira phan b6 va moi tradng la vin dl phiic tap va ddi hdi nhiing nghien ciiu chuyen sau Cac nghien cim eho den chi cho phep neu len mgt s6 nhan dinh ve quan he giiia phan b6 va dieu kien m6i tradng, chu trgng den hieu img ciia hien tugng nude trdi \^ Hinh 1: So phan b6 cua Diep quat (theo Vd ST Tuan, 1997b; viing dam la viing phan b6 tap trang) 66 N ll.-l- 11.^- • : • Phan R (f PbtiKtJ' f