KHOA HOC CONG NGHl
xiiVEiHIEIV CIJU AlXIH HLTOIXIG C U A PHUOIXIG P H A P K H A I T H A C OEIXI C H A T LUOIXIG CA IXIGU O A I DUOIXIG
O V I E T IXIAIVI
Trdn Diic Phiii T6MTAT
Ca ngii dai duong (ca ngir vay vang va ca ngir mat to) duoc khai thac bdng nghd cau tay k^t hgp anh sdng co chat lirgng thap hon ca ngir khai thac bdng cau vdng, ty Id ca dat Ioai A chidm 6,4%, loai B chidm 69,2% va B"
la 24,4%, tiong khi do, da sd ca cau vang dat chat lugng loai A (75,7%). Kdt qua nghien ciiu cbo thdy, chat lugng ca ngir cdu tay thap la do ca dirge keo len ngay khi cdn cau, nen c^ bi sg hai, vung vdy manh khi dua Idn tau, ddn ddn hien tuong sinh a xit trong co thit. Do ca vdn con sdng, ndn thuydn vien phai dung mdc d^
dua len tau va chay gd dap manh nhidu Idn dd gidt ca. Vi vay, ty Ie ca bi trdy xudc Ien den 14,5% va dgip thjt do chay g6 Id 8,6%. Kdt qud khao sat, phan tich, ddnh gia cho thay, ngu cu khai thic vd cudng do sang khdng anh hudng den chdt lugng ca ngir cau tay. Quy trinh so chd va bao quan ca ngir ciia nghd cdu tay vd cku vdng duoc thuc hien gidng nhau, nen day khong phai \k nguydn nhin Iim suy giam chdt Iugng ci ngir cau tay so vdi ca cau vang. Tuy nhien, su thidu thdn cac trang thiet bi sa che va bao quan da lam anh hudng ddn chdt lugng san pham. Ngu dan da diing true tiep nudc lam mit may tau de riia ci, cd khdng duoc ngam ha nhidt tnrdc khi dua vao bao quan va sir dung nudc di kb6ng dam bao ve sinh an toan thuc pham la nhflng nguydn nhan gop phan lam giam chdt lugng san pham. Bdn canh ket qua nghidn ciiu, trong bai bao cung dd xudt mgt sd giai phap vd quy trinh khai thac, so chd, bao quan va quan Iy dd cai thidn chdt Iuong ci ngir dai dirong cua ngh^ can tay.
Tli khda: Ca ngu ciu tay, ciu tay kdt hop anh sing, chit lmmg ca ngu, idiai thac ca ngir.
1. BAT VANH
Ca ngu dai dirong (cd ngir vdy va cd ngir mdt to) la mdt tiong nhirng mat hdng thuy sdn xuat khdu chii luc ciia Vidt Nam, xdp sau tdm vd ca tra, vdi tdng kim ngach xuat khau 526 tiidu dd la nam 2013 (VASEP, 2014). Ca ngir dai duong cung Id sd it loai hai san cd gid tri kinh td cao ma sdn lupng edn dudi miie cho phdp khai thdc. San lupng khai thdc nam 2013 Id 15.942 tdn (VASEP, 2014), hong khi san lupng cho phep khai tiidc khoang 21.000 tdn (Vidn NCHS, 2014). Tiem nang phdt trien nghd khai thac cd ngir dai duong trdn vimg bidn Viet Nam vdn cdn. Tuy nhidn, do chdt lupng ca ngir cau tay cdn thap, ndn gia tri xudt khau chua tuong ximg vdi tidm nang cua chiing.
Tir khi du nhdp vao Viet Nam tii nam 1994 ddn nay, cau vdng vdn la ngu eu chinh khai thac cd ngir dai duong. Cudi nam 2011, xuat hidn nghd khai tiidc ca ngir dai duong mdi, dd la nghd cau tay kdt hpp anh sang. Sau khi mgt sd ngu dan d huyen Hoai Nhpn tinh Binh Dinh lam nghe chup muc bdn tang gdng ket hop dnh sdng, ti-ong liie ranh rdi da su dung muc xa sdng lam mdi cau. Kdt qud rat bat ngd, trung binh mdi tdu cdu dugc 40 - 50 eon, san lugng binh qudn
dat 1,6 - 2 tdn/tdu/chuydn (Tran Due Phii, 2013).
Nghe nay da nhanh chdng phat trien ra edc tinh Phii Ydn va Khanh Hda la nhiing dia phuang vdn co truyen tiidng khai thdc ea ngir dai duong. Theo bao edo cua Chi cue Khai thac va Bao vd Ngudn lgi thuy san tinh Binh Dinh, Khanh Hda, Phii Ydn (2013), d^
eudi nam 2012 ea nudc (ehu yeu la khu vuc Nam Trung hg) cd khoang 3.500 tau khai thac ed ngir dai duong bang nghd cdu vdng va edu tay kdt hpp dnh sang. Tuy nhidn, tir nam 2013 den nay, ddi tdu khai i thdc ca ngir dai duong bang nghd can tay ket hgp anh sdng da da sut giam nhanh chdng do gid ca xudng rat thdp, ndn ngu dan da ehuydn sang nghe khdc hoae quay IEU nghe eau vang truydn thdng. Do qua tiinh phat hidn tu phat, ndn dat ra khdng it tiidch thiie cho eae co quan quan ly nhd nudc vd cdc nha hoach dinh chinh saeh.
Nghe cdu ca ngir dai duong bang cau tay kdt hop anh sang ed nhiing uu didm noi bat nhu sau: (1) vdn dau tu vd chi phi san xudt thap; (2) cdng nghd khai tilde don gian; (3) san lupng khai tiiac cao; (4) Al dang chuyen ddi nghd hoac khai thac kidm nghi Tuy nhidn, nghe nay ed han che rat ldn Id chdt lugng san phdm kem, ndn gia thdnh thap, din ddn vide lang phi ngudn loi do ton thdt ve gid tri san phara.
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Do gia thanh ca ngir dai duong dupc khai thac bang nghe cdu tay kdt hpp anh sdng chi bdng 1/2 so vdi ca ngir dupe khai thac bang nghe cdu vang, cd thdi didm gid cd ehi cdn 40.000 d/kg ndn xay nhidu tianh luan xung quanh van de ndy. Cdc nau vua cho rdng, do chat lupng cd giam ddn ddn gid thdnh cung gidm theo. Cd ngudi tiii cho rdng, do san lupng khai thac ldn ndn co sd thu mua cd tinh dp gid. Ngu dan thi nghi rang, do eudng do sang qua ldn ndn ldm chin thit cd ddn ddn chat lirgng giam. Cdc nha qudn ly vd nha khoa hpc ciing chua xac dinh dupc nguydn nhan thich dang cho van dd hdn.
Kdt qua nghidn ciiu dupc trinh bdy trong bai bdo nay nham gidi thich phan nao cho cau hdi lieu chat lupng cd ngir dai dirong khai thac bdng nghd cau tay kdt hpp anh sang cd thuc su gidm so vdi ed dupc khai thde bang nghd cdu vdng? Ndu chdt lupng thuc su giam thi nguydn nhan vi sao? vd cd nhiing giai phap gi de cai thidn?.
2. TAI UEU VA PHUUNG PHAP N G H C N C I I U
2.1. Hiu t h ^ sd lidu vd l^ra chpn tdu t h i ^ nghi&m
Dimg phidu didu h a dd thu mdu tai cae bdn cang, chu ndu vua va hdn tdu san xudt cua ngu ddn. Sd lidu tiiu thap lidn quan ddn gid thanh, chat lupng cdm Bang 1: Thang didm
quan, san lupng, chi sd ly hda (than nhidt, pH, dd cung CO thit), phan loai, kieh ed va khdi lupng cd.
Tren co sd phdn tieh cac ydu td hdn quan den van dd nghidn ciiu, nhdm nghien ciiu da lua chpn 01 tdu khai thac cd ngu dai duong bdng nghe cau tay kdt hpp anh sdng de thuc nghidm.
Tau thuc nghidm mang sd dang ky BD 95930 TS, cdng sudt 90 CV, do dng Nguydn Van Ddng Idm chu, dugc cap phep boat ddng nghe eau tay kdt hgp anh sang, sd luong thdg cdu gdm 4 theo (8 ludi cdu), dimg mue xa sdng lam mdi eau. Do didu kidn khdch quan ndn vide thue nghidm ciing chua ttiuc hidn dupc trdn nhidu tau, dd eung chinh Id han chd ciia kdt qud nghidn eiiu.
2.2. Phuong p h ^ ddnh gid cdm quan Vide ddnh gia cam quan dugc thuc hidn bdi cac ehuydn gia ddnh gia cam quan. Vide ddnh gid cdm quan dupc thuc hidn thep phuong phap cho diem cua Tdng cdng ty Thuy san Bidn Ddng (Nguydn Chinh Tdm, 2006). Cdc cd the cd dtrpc ddnh gia cam quan bdi 5 chuydn gia cam quan cd kinh nghidm trdn 15 ndm hong linh vuc danh gid cam quan thuy san. Cac chuydn gia ndy dtroc hudn luydn trudc khi danh gid chinh thiic. Thang didm ddnh gia cam quan dupc trinh bay d bang 1.
ddnh gid cdm quan Chi tidu
camquan
ll g
Mau sdc Didm
50
40
30
20
10
50
Chat lugng Rat tdt
Tdt
Trungbinh
Kem
Rdt kem
Rdt tdt
Mdtd
Khdng CO khuydt tdt (khdng rdch, hdy, hi khia vao, bam dap). Vdy nguydn ven, ea hdng nhu mdi vdt dudi nudc ldn. Mau ea sang, thit rat ehac, nhanh ddn hdi trd lai khi dn nhe ngdn tay vao. Khdng cd chd ndo mdm hdn minh ca.
Cd khuydt tdt nhe (cd vdi vdt rdch, bdm dap, khia vao, hdy da nhd).
Mat mdt sd vay, mau hoi xam mdt chiit. Thit chae, eham dan hdi h d lai khi dn nhe ngdn tay vao. Cd 1,2 ehd rat mdm rat nhd tren minh cd.
Cd khuyet tat rd (tdi da hai vet rdch, bdm gidp, khia vdo, tray da ed the anh hudng ddn lupng thit thu dugc). Mdt mdt vdi mang vay nhd.
Mau xam/den. Cd trieu chimg ngam nudc hoac bidn mau dd. Thit khdng chac, khdng dan hoi trd lai khi an ngdn tay vao. Cd mdt chd mdm nhd hen minh cd.
Cd hon hai vet rdch, bdm giap, khia vao, trdy da ed the anh hudng den lupng thit thu dupc. Mat timg mang ldn vay. Mau ca sdm. Bae mau bidn mau do rdt ro rang.
Mmh ea dap ndt, bidn dang nghiem hpng. Mdt rdt nhieu vay. Mau ca sdm. Bae mau bien mdu nghiem trgng. Thit rdt nhao, ra ra timg phdn, minh ea gay rdi. Thit da bdt ddu cd ky sinh trimg hoae bi bdnh.
Thit hong md, bdng. Mdu sang. Thdy rd md ldp ngoai.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 1/2015 105
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Ddn hdi
Miiivi 40 30 20 10 50 40 30 20 10 50 40 30 20 10
Tdt Tnmg binh
Kem Rdt kem
Rat tdt Tdt Trung binh
Kem Rat kem
Rdt tdt Tdt Trung binh
Kem Rdt kem
Thit trong md it va kem bdng, mdu kem sdng, md chi hoi thay d ldp ngodi.
Thit hong md va mdt dd bdng, mdu hoi xdm va nga nau; khdng cd md d ldp ngoai.
Thit hodn todn md due, khdng bdng, mau nga nau vd xam rd, khdng cd md d ldp ngodi.
Thit md due, mau nau, bac hang hoac xdm, khdng cd md d ldp ngodi.
San chde San ehac, ddn hdi h ddn hdi
Thit mdm nhao, khdng dan hdi Mem nhao, dinh
Mui rong bidn, nudc bidn, ngpt, man, kim loai, bo Miii trung tinh, khdng mid
Mui cd, thiing bia ciing (carton) udt, di nhe Mui chua nhe, mui oxy hda nhe Miii amoniac, miu thdi, miii phdn Sau khi tdng hpp didm sd cua timg ca thd, kdt
hpp vdi thuc td thu mua cua ede ehu nau, tien hdnh phan loai cd nhu sau: Loai A = 41-50 didm (dat tidu chuan hang di mdy bay); loai B = 31-40 didm (dat tidu chudn ldm hdng xdng CO cao cap); loai B" = 21-30 didm (dat tidu chudn ddng hop); loai C < 20 didm (tidu thu ndi dia).
2.3. Td chiic thuc nghidm xdc dinh nguydn nhan 2.3.1. Thu nghiem thay ddi tdc dd thu ciu Khi cd an cau, cho thuy Ihu cdt theo cdu cd ca vdo phao ndi. Thdi gian budc cd vao phao la 01 gid.
Giira phao ndi va tdu cd ddy Udn kdt vdi nhau dd theo ddi phao va hoat ddng cua ed. Muc dich cua phirong phdp nay la tao su ddng nhdt cdch thu cdu giiia nghe cdu vang truyen thdng vd cdu tay kdt hgp dnh sang.
Tiic Id h ^ ehd dupc Iuc keo cua ngudi ddi vdi cd va chi cdn luc keo cua ed ddi vdi vang cau. Nhu vay, cd khi an cdu se chay quanh phao khoang ttidi gian 45 - 60 phiit, khi dd ea da ydu ddn vd sau dd bat ddu kdo cd ldn tau mat Idioang 5 phiit.
2.3.2. Xa miu tiiet dd
Khi thay ea dn cdu, eho thiiy thu thu edu binh thudng. Sau Idii dua cd ldn tdu, tidn hdnh gidt chet ed, xa mdu, loai bd, rudt, mang vd lam saeh ed. Sau khi cd dtrpc ldm sach, quan sat vidn tien hdnh ghi sd mdu va ldm ddu trudc khi chp cd vap hdm bao qudn.
2.3.3. Thu nghidm thay ddi nguon sing Khi ed ca an cau, eho thuy thu thu cau nhu bmh thirdng, tidn hdnh tdt ngudn sang theo trinh tii nhu
+ Ban dau, cho thuydn trudng tat cdc ddn ed anh hudng true tidp den san phdm tiic Id cdc bdng ddn b gdn vi tri thu cdu.
+ Sau khi thu cau dirge 1/2 ddy eau, tidn hdnh cho thuydn tnrdng tat cdc den cdn lai cd anh hiroiig ddn san pham tnrdc khi dtra ldn tau.
-1- Cac den khdng true tidp anh hudng ddn san pham dirpc giii nguydn dd khdng anh hudng ddn qui trinh khai thae.
Sau khi ca dupc dua ldn tdu, tidn hdnh gidt ch^t ca. Sau khi so chd xpng, quan sat vidn tidn hdnh ghi sd mdu va lam ddu trudc khi cho ea vdo hdm bao quan.
2.3.4. Liy miu, cd dinh miu phin tich cic chi tidu cam quan, hda ly
Ddi vdi ldy mdu danh gia cam quan: Ddnh gia true tiep hen timg cd thd ed, dua vao cdc dae tinh bdn ngoai kdt hpp vdi xdm thit ca khi mdi eau dua ldn tdu cflng nhu khi tdu cap bdn.
Ddi vdi ldy mau phan tich cae ehi tidu hda ly:
Mdu dupc lay d ba vi tri dau, giua va dudi, sau d6 dirge hpn lai va ddng nhdt bdng may xay tiiit (Super Blender, MX - T2GN, Matsushita Electiic Industtial Co., Ltd, Japan). Mdi eon ed dupc chia ldm 4 loin (thit than), ldy mdu phdn tich hda \y dupc thuc hidn if phdn loin bung. Qud trinh ldy mdu nay dugc thyc hidn ngay khi tau vd cang ea. Phuong phdp phdn tich mdu thu dupc bang mdy phan tich cdc chi sd hda, ly....dirge thuc hidn 6 phdng thi nghidm.
2.4. Ky fliu^t xtr 1^ sd lidu
Sd lieu duoe xu ly bang phdn mem tiidng kd 106
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SPSS 14.0 (SPSS hie., Chicago, IL, USA). Cdc tiiue nghidm dugc thuc hidn vdi do lap Iai it nhat ba lan dd tidn hdnh phan tich ANOVA Kidm dinh Tukey dirge ttiuc hidn de danh gid su khdc bidt cd y nghia thdng kd giua cae kdt qua vdi miic y nghia p < 0,05.
XKHQUiiNGHBICUU
3.1. Thuc trgng ch^t lupng cd ngu dai duong cau tay kdt hpp dnh sdng dupc thu mua tai cdng
Kdt qua danh gia chat lupng cam quan ca ngir khai thac bang cau vang vd cau tay ket hgp dnh sdng dtrpc thu thap tai cang cd cho thay: chdt lugng ca ngir cau vdng tdt hon nhieu so vdi cd ngir cau tay kdt hpp anh sang (do thi 1).
90
sa
60
^
•<m
HO
10
± •
• 1
• 1 1,
A
1 I
• 1
J • im
B
1 m
M
B . a . a,T C Xep loai Dd thi 1: Anh hirdng ciia phuang phdp ddnh bdt ddn
chdt lugng cam quan cd ng^ khai thdc Dd thi 1 eho thay, ca ngir khai thdc bang eau vang cd ty Id dat loai A cao hon gap nhidu ldn (75,7%) so vdi ea ngu eau tay, ehi dat 6,4% (vdi p < 0,05).
Ngupc lai, ty le ea ngir khai thac bang cdu tay kdt hpp anh sdng xep loai B va B" cao hon so vdi cd ngir cdu vdng, ty Id tirong ung cua chiing la 69,3% vd 23,4%
so vdi 22,4% va 1,9% (vdi p < 0,05).
Vdi ly Id ea xd'p loai B va B" rat eao (khoang 92,7%), do dd gia ca ngir dai duong cdu tay kdt hgp aiih sang ludn thdp hon cau vang. Day la ket qua danh gid cam quan eua nhimg ngirdi thu mua, tuy nhidn chat luong that su cd khae bidt Idn nhu vay khdng thi cdn phai nghidn ciiu, ddnh gia chinh xde va khoa hpc hon.
3.2. Anh hudng ciia phuong phdp ddnh bdt ddn chdt lugng cd ngir dai duong
Cau tao eiia ngu cu diing de khai thac cd ngir dai duong la hd thdng cau. Bao gdm hai bd ph§n chinh la ludi cau (chii J hoac chii C) vd theo cau, cimg vdi Ihidt hi phu trg khdc nhu ma ni, dng lot, phao, chi, edn cau... Quy trinh khai thdc eung hdt siic don gian.
Mdi cau (muc xa sdng) duge mde vdo ludi cdu va thd xudng do sdu 50 - 80 m, ngam eau ddn khi nao ea can cau thi keo ldn. Trong qua trinh ngdm cau thi ngu dan bat hd thdng den cao dp dd du cd (khoang 15 kW). Vi vdy ngu dan gpi day la nghe cau tay ea ngir dai duong ket hgp anh sang.
Kdt qua nghidn ciiu cho thay, qua trinh tha, thu cdu khdng cd ydu td Idm tdn hai co hgc ddi vdi ca.
Thdng thudng ludi cau mde vao mep eua cd, day la phan xuong (Hirtii 1) ndn khdng lam tdn hai den eo thitca.
Hinh 1: Cd mdc vdo luoi can Tuy nhidn, cdch thiic dua cd Idn tdu tidm am
nhieu yeu td cd the lam giam chat lugng ea ngir eau tay so vdi cdu vang. Kdt qua khao sat eho thay, 100%
cd dua ldn tau cdn sdng. Do dd, khi keo ldn den mat nuoc, ca giay giua rdt manh, thuydn vidn phai dimg mdc nhieu ldn mdi dua dupc ea ldn tau. Vi vay ty Id cd
bi hay xudc Id kha cao (14,5%). Sau dd, thuyen vien dimg chay gd dap nhidu ldn vdo dau vd lung dd gidt ca ndn lam tdn hai den thit cd. Do dd, cd ddn 8,6% thit ca hi dap do bi chdy dap. Ngupc Iai khdng cd trudng hpp ndo cd bi hay xudc do ludd eau gay ra. Sd lieu eu the dupc thdng kd d bang 2.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 1/2015 107
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Bang 2: Tinh tnmg cdkfai dua len tiu Tinh trang
Tyle (it)
Ca van con song khi dua len tau
100
Cdtrayxuocdo moc keo
14,5
C i bi tray xuoc do luGicau
Ca dap thit do chay dap (%) Ket qua nghien cuu cho thay, qua trinh dua ca
ten tau va gift ca la mot trong nhung nguyen nhan lam giam chat luong ca ngir dai dttong khai thac bang ngh4 cau tay ket hop anh sang.
3.3. Anh huong dia tdc dO thu c4u Sin chiit lugng cd ngit dai duang
Theo auv trinh khai thac thong thuong cua ngir
dan, thoi gian til liic ca cin cau den khi dtra ca ten tau dita ra rat nhanh, trung binh khoang 2 phut 40 giSy (TrSn Due Phli, 2013). Theo gia thuyA dat ra, sau khi ci cin cau, ti& hanh tha phao ngam ca du4i nuoc 45 - 60 phiit de ca giam so' hai, yfa ddn vi giiy dua giam roi mdi keo Ita tau.
Hinh 2. Tha phao d6 ngdm c^u khi cd an c ^
Bang 3. Su thay d6i cdc chi s6 h6a hoc ddi v6i m l u thii D g h i ^ vd mdu d6i chucng Chi so
Dp Cling ciia co thit (g) Do dinh cua ca thit (gf.cm) Ham luong t6ng axit bay hcd (%) Ham luong axit lactic (%) Ham lirong dam t^ng s6 (g/lOOg) Ham lupng NHs (g/lOOg) Chi so peroxit (nmol/lOOg) Chi so TBABS (mg MAD/lOOg) Ham lupng histamin Di^m cam quan trung bmh
Mdu thuc nghiem Thu cdu ngay lap tire khi ca
cin cdu (mlu d6i chiing) 5.602 -61,4 1,231 1,077 21,27 24,58 34,62 0,045 35,0 31
Ngdm cau 1 gia sau khi cd can cau (mdu thu nghigm)
5.822 -74,5 1,023 0,920 23,50 18,09 22,74 0,030 24,3 40 Kdt qua phdn tich hdn cho thdy, tat ca eae ehi sd
hda hoe va cam quan cua mdu thir nghidm ddu tdt hon mdu ddi chiing. Dac bidt la ham lupng axit tdng va axit lactic giam xudng dang kd tir 1,231% va 1,077%
xudng cdn 1,023% va 0,920%. Dieu ndy cd y nghia d^c bidt, vi chinh hdm lupng axit tdng va axit lactic gdy ra vi ehua cua ea va lam cho chdt lupng ca suy giam.
Ngodi ra, diem cam quan tiimg binh dugc cai thidn ddng kd tir 31 didm ldn 40 didm. Ddi vdi co sd thu mua chi dua vdo ciii sd ndy dd quydt dinh gia thdnh sdn phdm. Didm cam quan cang eao thi chdt lugng ea
cdng tdt vd gid thdnh eang cao.
Nhu vdy, chdt lugng cua ed ngir duge cai tiiidn dang kd ndu ngdm ca dudi nude mdt thdi gian dd c^
giam su sp hai vd vimg vdy, ydu ddn rdi mdi dua ldn tau. Dieu nay hodn todn phu hgp vdi thue td. Chdt lupng ea ngir eau vang duoc ddnh gia tdt hon la do tdc do thu cdu cham, ca it phan khdng, it vung vdy, khi ea kdo ldn tdu Id da yeu rdi. Trong khi cd cdu tay cd su phan khdng vd van ddng nhidu hon, ndng dO pH bidn ddi nhidu hon ndn chdt lupng cd thd hi bidn ddi xdu hon ca eau vdng. Bdi vi vd mat cam quan vd 108
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cdng nghd thi dp pH cua cd du bidn ddi rdt nhd nhung cd tam quan ti-png rdt ldn (Huss,1995), pH sau khi cd chdt la ydu td quan hgng nhdt cd anh hirdng ddn eau tnie cua thit ea vd miie dg ran nut cua md Hdn kdt, gay diit gay md Hdn kdt, thdm chi nhirng bien ddi rdt nhd cua pH cung tac dOng rdt m ^ h ddn cae thudc tinh cua md Hdn kdt. Dp pH cua ea sau khi chdt ed Hdn quan ddn sir van ddng cua md co va eae phan ling sinh hda hpe xdy ra khi vdn dpng.
Tir cdc kdt qua phan tich trdn, cd thd kdt ludn rdng: tdc dp thu cdu cd anh hirdng rdt ldn den chdt lupng ca ngir dai dirong. Cd dugc ngam dudi bidn sau khi cdn cau mdt thdi gian rdi mdi dua ldn tau cd chat
lugng tdt hon ea dugc kep len ngay l^p tiic khi can cau.
3.4. Anh hudng ciia cudng dO sdng ddn chdt lupng cd ngir d ^ dirong
Vdi gia tiiuydt dat ra Id eudng dO sdng qua manh da Idm cho cd bi sdc, chin thit va la nguydn nhdn ldm giam chdt lupng ea ngir dai duong khai thde bang nghe cau tay kdt hpp dnh sang. Nhdm nghidn ciiu da tidn hanh do nhidt do nudc bidn d do sau 1 m, nhidt do khdng khi trdn boong tdu dudi bdng den 1,5 m, nhidt dp khdng khi hen boong tdu khi tat den va nhidt dp be mat da cd. Kdt qua duoe the hidn qua do tili 2.
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Dd thi 2: Nhidt dO ciia nudc bidn, Ididng khi trdn boong tdu vd cua bd m$t da cd Kdt qua khao sat va thue nghidm cho thdy, nhidt
do trung binh cua nudc bidn 24,92'*C, cua khdng khi khi ed den 23,58''C, khi khdng ed den Id 23,50''C, cua bd mat da cd 24,47*'C, thdn nhidt ca d dp sdu 10 em la 27,25"C, dieu nay chung tb anh sdng cua den khdng lam tang than nhidt ciia ca.
Vi vay, ed the khang dinh, den khdng phai la nguydn nhan gdy sdc, tang nhidt dp vd gdy cang
thdng, lam giam chat lupng va ldm cho ttiit ed nhanh bi hu hdng hon khi bdo qudn.
3.5. Anh hudng cua phuong p h ^ so chd vd bao quan ddn chdt Iupng cd ngu d ^ duong
Kdt qua khdo sdt cho thdy quy trinh so che va bdo quan ea ngir dai duong bdng nghe cau tay kdt hpp anh sang va edu vang duge ngu dan ttiuc hidn hoan todn gidng nhau, cd thd tdm tat bdng so dd sau;
Gilt c& cat v^y Bd nOi tang Riia sacli Dua xuong ham bao quan So dd 1: Quy trinh so chd vd bao quan
Do quy trinh so chd va bao quan cd ngir dai duong ciia hai nghd khai thae gidng nhau ndn ed the kdt ludn chdt lupng cd ngir dai duong bang nghd cdu tay kdt hgp anh sang thap hon ca ngir cdu vdng khdng phai do quy trinh so che va bao quan san phdm gay ra.
Kdt qua nghien ciiu, khao sat eho thdy quy trinh vd trang thidt bi dimg dd so ehd va bdo quan cd ngir dai duong tidm an nhieu ydu td anh hudng ddn chdt lugng ca ngir dai dirong. Dung cu so chd gdm cd chay gidt cd, cua cat vdy va dao cat mang, ndi tang.
cd ngir dai duong trdn tdu khai thdc
Ham bao quan thi khdng dam bao chdt lupng va giii nhiet tdt.
Khi dua Idn tau, ca khdng dupe giet chdt nhanh bang phuong phdp chpc tiiy sdng (Pham Ngpc Hde, 2006) md dimg chay de giet ca ndn cd giay giua, va dap rdt manh vao san tau. Ngoai ra, hdu het cae tdu cau tay ket hgp anh sdng khdng dimg dem Idt (chi 1,45% hang bi) khi dua cd ldn tau nen khi gap sdng to, gid ldn, cd bi va dap cdng nhidu.
Sau khi loai bd vay, mang va ndi tang, ngu dan dimg nudc lam mat may de riia cd. Nudc lam mat NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 1/2015 109
KHOA HOC C 6 N G N G H l
may khdng dam bao vd sinh, nhidt dp cao hon than nhidt cua cd (SCC so vdi 27°C), ddn den lam tang nhidt dd be mat cua ea. Do dd, thdi gian ldm Ianh ca se lau hon khi dua vdo ham bdo qudn. Thdi gian ldm lanh cdng ldu thi chat lupng ed cdng giam (Huss, 1995).
vat Hdu cdch nhiet cua hdm bao qudn Id xdp ghep dupc bpc vdn gd bdn ngodi ndn khd ndng giii nhidt khdng cao. Trong khi chuydn bien 1 5 - 2 0 ngdy ndn ngu ddn phdi bd sung da hang ngdy, nhung nudc dd khdng dupc kidm soat vd sirdi - an todn thuc pham. Nudc da khdng kidm sodt dupe ngudn gde, ve sinh vd an toan thuc pham gdy ra mdi nguy vd vi sinh vd hda chat dpe hai. Bdn eanh dd, nudc da non khdng dii dp lanh la mdi nguy gay ra hidn tupng du lugng nhung khdng du lanh ldm cho san pham khdng dam bao chat lugng, tang nguy co gdy tdn thdt sau thu hoach cho cac tau ca xa bd.
Cd khdng dugc ngdm ha nhidt trudc khi dua vao bdo quan cung Id nguydn nhdn ddn den giam chat Iupng cd ngir dai dirong. Theo Pham Ngpe Hde (2006) khi ngdm ha nhidt trudc khi dira vdo bdo quan se ldm cho cd lanh ddu va nhanh hon, chat lupng dugc duy tri tdt hon.
Nhu vdy dung cu thd so, cd khdng dugc gidt chdt nhanh, khdng xa mdu tridt de, ngam ha nhidt trudc khi bdo quan da anh hudng rat ldn ddn chat lupng ca ngir dai dirong. Do dd edn nit ngan thdi gian so che, ngam ha nhidt tnrdc khi dua vdo bdo quan se gdp phdn cai thidn dugc chat lugng cd ngir dai duong.
4. NET LUM Vli K ^ NGHI 4.1. Kdt luan
Chat Iupng ea ngir dai duong khai thde bang nghd cdu tay kdt hgp dnh sdng thdp didm vd cam quan hon so vdi cd khai thae bang nghd cau vang.
Khoang 92,7% ca cdu tay dupc xdp Ioai B va B", trong khi dd ty Id cd dat Ioai A ehi chidm 6,4%. Ngugc Iai, 75,7% ca cdu vang dat loai A Dd la nguydn nhan ddn ddn gid cd ngir cdu tay thdp hon cd can vang.
Nguydn nhdn chinh ddn ddn chat lupng ed ngir cdu tay giam so vdi cdu vdng dugc xdc dinh Id do tdc do tiiu cdu qud nhanh ddn den ca phan khang manh hdt lam can kiet edc chat gidu nang lupng (glycogen va ATP) Idm tich luy a xit, ttiit ca bi ehua vd chat lupng nhanh chdng bi xudng cap.
Cdng nghd khai thdc vd eudng dd sdng khdng anh hudng den chdt lupng ca ngir cdu tay. Tuy nhidn.
qud tirinh dua ca ldn tau va gidt cd tidm an nhidu y^
td cd thd anh hudng den chat lupng ca ngir nhu hau hdt edc tdu ddu khdng su dung ddm Idt, cd hi tiiy xudc do mdc, dung chdy gd dd gidt ca,...
Qud trinh so chd va bao quan hdn tau tidm an nhieu nguy eo lam anh hudng ddn chat lupng ca ngft d^ duong.
4.2. Kidn nghi
- Ve qui trinh khai thac, cdn nghidn ciiu phuong phdp ldm td Hdt ca dd tranh sir phan khdng ciia ca tnrdc khi keo ca ldn tau.
- Vd phuong phap so chd tnrdc khi bao qudn san phdm, can tdp trung ldm tdt hon mdt sd vide nhu sau;
(1) Trang bi dung eu giet nhanh dd trdnh cd vung vdy, va dap nhidu trudc khi chdt; (2) hang hi du phuong tidn, dung cu chuydn dimg cho nghd cdu ca ngir dai duong dd han che tdi da su va ddp giiia cd voi tau; (3) tuan thii diing quy trinh xu ly-xa mdu-bo mang vd ndi tang-rua sach trudc khi bao quan; (4) dimg nudc bidn sach, Ididng dimg nudc lam mdt may dd rita cd; (5) nhu ydu phdm cdn dd ridng khdng de chung vdi san phdm hong qua trinh bao quan, dd xay va bd sung dd xay cdn bd tri hpp ly tranh ddng mo ndp hdm nhidu ldn; (6) sii dung nudc dd sach va lanh du dp, khdng dting nude da bdn, nudc da non khdng du dd lanh; (7) ddu tu thidt hi ngdm ha nhidt tiuoc khi dua san phdm di bao quan.
- Ve cdng nghd bao quan san pham, cdn nang cap hdm bag quan hdn tau khai thdc cd ngir dai duong bang vat Hdu each nhidt tdt PU, hdn tdi lap dat hdm cdp ddng hoac dp dung he thdng tudn hoan nudc bien lanh dd lam lanh nhanh sdn phdm.
- Ve giai phdp vd quan I^ nha nudc, cdn t^p trung lam tdt cdc cdng vide sau; (1) nghidn ciiu cdn bdng sfl lugng tau thuyen tham gia nghd eau tay ca ngir dai duong vdi cac nghd khae, h-anh tmh hang qua tai nghd dnh hudng ddn ngudn lgi vd gia ban san pham;
(2) cd nhimg bidn phdp dn dinh gia ban vd tim ki6n thdm nhieu Ihi tnrdng cho ddu ra eua san phdm ca ngir dai duong; (3) dau tu nghidn ciiu thdm vd chat lugng san phdm cua nghe cau tay va nhiing giai phap khoa hgc-cdng nghd cu tiid, td chiic thuc hidn c6 hidu qua hon; (4) dau tu, hd trg vd thudng xuydn to chiic cdc ldp tap huan cho ngu dan nghd cdu tay.
TAI UEU THAM MttO
1. Chi cue Khai thac va Bao vd Ngudn Ipi Thiiy san tinh Binh Dinh, 2013. Bdp cao tiiudng nidn tdng ket hoat ddng khai thac thiiy sdn.
110
KHOA HOC C 6 N G NGHl
2. Chi cue Khai thdc va Bao vd Ngudn lpi Thuy xuat giai phdp". Du an Bd Ndng nghidp va Phat trien san tinh Khanh Hda, 2013. Bdo cao thirdng rudn tdng Ndng ttidn, ndm 2012 - 2013.
kdt hoat ddng khai ttiac tiiuy san. 6 Nguyen Chinh Tam (2006), Kf ttiuat khai ttiac 3. Chi cue Khai thdc va Bao vd Ngudn Igi Thiiy cd ngir dai dirong d tdng edng ty hai san Bidn Ddng- san tinh Phii Ydn, 2013. Bao cao thirdng nidn tdng Tdng kdt nghe eau cd ngir dai dirong. Nha xudt ban ket hoat ddng khai thac thuy san. Ndng nghidp.
4. Pham Nggc Hde, 2006. Ky thuat bao quan sau 7. VASEP, 2014. Bdo cao xudt nhap khau thuy thu hoach, che bien cd ngir trdn tau va tai nha may, sdn Viet Nam nam 2013.
dich vu hau edn phue v^ cho ddi tdu khai tiiac cd ngu g yign Nghidn ciiu Hai san (Vidn NCHS), 2014.
tai Tmdng Sa- Tdng kdt nghe edu ed ngir dai duong Hidn trang ngudn loi hai san d bidn Vidt Nam giai (2006). Nhd xuat ban Ndng nghidp. ^ ^ ^ 2011 - 2013. Tap chi Thdng tin Thiiy san, sd
5. Tran Diic Phu vd cgng tde vidn, 2013. Bao cao 1/2014.
tdng kdt du an "Didu h a ttiuc trang bao quan sau tiiu g HUSS H. H . , 1995. QuaHty and quaHty changes hoach sdn phdm khai tiiac hdn tdu ca xa bd vd dd ^ ^^^^ ^^-^ P^O^ ^^^^^ 1995
RESEARCH ON INFLUENCES OF FISHING METHODS ON VIETNAM'S TUNA QUALTIY Tran Due Phu Summary
Quality of tuna caught by handline with artificial Hght was worse than that of longline. The rates of tuna caught hanline witii Hght ranked B and B" grade were 69.356 and 23.4% respectively, while tuna rannked A grade accounted only for 6.4%. By contiast, the rate of tuna caught by longline was ranked A grade by 75.7%.
The reason of low quality of tuna was quick speed of hauling. Luie hauling was conducted inmediatiy when hooking, led to fiight and struggle offish. Acid was bom during violent struggle stage of tuna, and therefore fish meat would be sour. The research defined that hooks and high light power were not effect on tuna quality, but handing fish up and kiUmg processes have impacted fish quality. The process of pre-processing and fish handling technology of handline and longUne were similar. However, lack of handling equipment onboard have impacted tuna quality. 14.5% and 8.6% tunas were scratched all over and broken because of fish caught tools and hammer. Also, fishers have not carried out fish icing before convervabon and used dirty water and ice, which leaded to low quaHty. In addition, the paper puted forward the solutions to improve fish quaHty, including fishing technologies, pre-processing, fish handling and management measures.
K^ words: Tuma canght by handbne, caught by handhne with artiScinl hght, quahty of tuna, tuna explanation.
Ngudi phan bi^n: TS. Chu Tidn Vinh Ngdy nhdn bdi: 18/8/2014 Ngdy thdng qua phan bidn: 18/9/2014 Ngdy duy^t dang; 25/9/2014
NONG NGHIEP VA PHATTRIEN NONGTHON - KY 1 - THANG 1/2015
