KHOA HOC CONG NGHl

KHOA HOC CONG NGHl

DAIMH G l A V A I T R D CLIA RDIMG BIEIM V A T H U C V A ^ THLIY S I M H TRDIXIG A D IXIUOI TDIVI QUAIXIG CAIMH

CAI TIEIM D H U Y $ I \ I D A M D D I , TilMH CA M A U

N g u y ^ Thi Ngpc Ahh\ Nguyen H o ^ Vinh^•^ Lam My Lan', Trin Ngoc H^'

T6MTAT

Khao sat duoc ti^n hanh bang cach phong van true Dep 90 hQ nuoi torn sii quang canh cai U^n ( Q t ^ I ) a huyen DAm Doi, linh Ca Mau nham danh gia vai tro va tac dong cua rong bi^n va thyc vgt thiiy -^mh (TVTS) d^n nang suat va loi nhuan ciia mo hinh. Cac hp nuoi tom QCCT dupc chpn phong van chia thanh 3 nhom vk tinh trang rong bi^n va TVTS xuat hien tu nhien trong ao. Nhom 1: ao nuoi t6m QCCT co su hi^n di^n tu nhien cua nhieu loai rong bi^n va TVTS nhung khong co rong cau (rong hfin h)^), nhom 2. ao nuoi tom QCCT CO rong cau xuat hi^n tu nhi^n uu th& hon cac loai rong bi^n va TVTS khac va nhbm 3: ao nuoi torn QCCT khong c6 su hien di^n ciia ronji bien va T \ T S nhung co su hi&n di^n ciia c&y AaOc ho^c cay mam chit^m 20-30% di^n lich ao. Ket qua khao sat tu y kien nong hO cho bi^t c6 4 loai rong bi^n (rong cau Gracilana. rong xanh Cladophoraceae. rong biin Enleromorpha va rong nhol Spirogyra) va 3 I091 TVTS (rong da Najas, rong duoi chon Ceratopbylluni va c6 nan Eleochans) thuong xuat hi<'n ti; iihi^n irong ao nu6i tom QCCT, trong do rong cau dirgrc ua thich duy tri trong ao nuoi nhicu nhat (35% so ho), Vi- den la rong da (23,3% s6 hfl), cac loai rong khac co ti le diap hon. Da so y ki^n nong hO OSl.7-91.7%) cho ring rong bi^n va TVTS co vai tro quan Irpng Irong ao nuoi torn QCCT nhu cai thi^n chat lirong mroc. lAm ihirc an true tifip, noi tni an cho tom, cua va lao ngudn thuc an lu nhien. B&n canh do. khi phat Inen qua muc chiing cung gay ra mot so tro ngai nhat dinh nhu lam nuoe ao rat trong, gay thoi nuoe khi lan lui. can tro hoal dpng song ciia torn, cua va lam giam nang sual torn nuoi. Nhom 2 dat nang suat tom sii va Igi nhu^n cao nhat (336,8+92.7 kg/ha/nflm va 70.2+26.4 tneu d o n g / h a / n a m ) , kei d^n la nhom 1 (282,1±122.2 kg/ha/nam va 57,8+29.0 In^u dong/ha/nam) va hai nhom nay cao hon co y nghia thdng kfi (p<0.05) so voi nh6m 3 (107,7±42 k g / h a / n a m va 39,0±17,1 tnfiu dong/ha/nSm). Ngoai ra, ao nuoi t6m QCCT duy In dO phii rong bi^n va TVTS <50% thu dupc nang suat lom sii va Igi nhuan cao hon nhi4u so voi ao co dO phu >50% va ao nuoi tdm QCCT khong co rong bi&n va TVTS.

Tli kh6a; Ao nuoi tdm quang canh cai den, rong bie'n. thuc vat thiiy smh, do pbu. nang su.it, Icn nbuan

1. BAT VAN BE ^^^ ^^^'^ nghin ha, d^c bi$t la h u y e n Dam Doi co . , h o n 62 nghin h a di^n tich nuoi trong thiiy san vol D o n g b a n g s o n g C u u Long ff)BSCL) co n h i e u ^ j ^ . . ^ ^ . ^^^ j ^ . ^ ^^^^ ^^^ tam-rim^. torn cong t h u a n Igi v e dieu kien t u n h i e n va tiem n a n g ve di^n ^^^.^^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^^^^^^^ ^ ^^ ^ . ^^^ ^^.^

tich nuoi t r o n g t h u y san. Ia viing nuoi torn n u o e Ig ^ . ^ ^^ ^ ^ ^ ^ ^ ^ ^ . ^ ^^^^ ^^^^ ^^^ ^^^ ^ t r o n g d i e m c u a ca niroc vol n h i e u h i n h t h u c nuoi c^a. j - .• i. •-. c u

'^ . 50% dien tich nuoi toan tmh.

k h a c n h a u . T r o n g do nuoi torn q u a n g c a n h cai h e n

(QCCT) c h i e m p h i n lon do chi phi t h i p , k y t h u a t RonR bien va t h u c vat t h u y s m h (TYTS) co vai d o n gian va p h i h p p vol di6u kien c a n h tac ciia n o n g l^" " t q u a n t r g n g ffong c a c h e sinh thai lp, man.

h o . d u o c x e m la m o h i n h nuoi b i n v u n g va t h a n thien C h i i n g la noi c u t n i , vuon u o m nuoi iu trung, sinh vol moi t r u o n g va dltoc nuoi p h o bien 6 cac tinh ven ^ ^ S va sinh san ciia rat n h i t a loai thiiy hii san, co bien D B S C L n h u Ca M a u . B a c Lieu. Ben T r e . . . > * * " ^ n g h a p thu m a n h cac c h a l dinh dirong trong ( T n n h T h l Long va D u o n g C o n g C h i n h , 2013; m « t™™K Smp dieu hoa va can b a n g he sinh thai N g u y e n T h a n h P h u a n g va ctv.. 2014). T h e o S o N o n g (B>nh T h . P h u o n g Anh va H o a n g Thi Ngoc H . ^ U , n g h i e p va PI-NT tinh C a M a u , dien tich nuoi t o m 201°; J a i k u m a r , et al., 2011; Hurd, « ^,_ 2014;

Q C C T lien t u c l a n g . tir n a m 2010 d e n n a m 2018 co V a h e e d a , va Simon 2014; O U a r e , et al. 2018). QI DBSCL, r o n g bien va T \ T S d u p c tim thay quanh n a m t r o n g cac thiiy vuc n u o e l p va ao nuoi torn ' Khoa Tliu> san. Trucmg Dai hoc c i n Tho Q C C T viVl sinh l u p n g 1cm (ITB-Vieliiam, 2011 ' Trung lam Khu\cn nong, Khuyen ngu Bac Lieu N g u y e n Thi Ngpc A n h , 201.5). T u y nhien, vai irn ' Email; ntnanh@clu.edu \ n

116 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 11/2019

KHOA HOC CONG N G H f

tac dpng cua rong bien va TVTS trong ao nuoi tom QC(-T khac nhau theo loai va muc do phat trien ciia chung (ITB-Vietnam, 2011; Jaikumar. et al., 2011;

Nguyen Thl Nggc Anh va ctv., 2017). Vi the, muc tieu cua nghien cuu la nham tim hieu vai tro cua cac loai rong bien va TVTS hien di?n tu nhien trong ao nuoi torn QCCr va anh huong cua chiing den hieu qua tai chinh ciia mo hinh nuoi a huy^n Dam Doi. tinh Ca Mau. K^t qua co the cung cap thong tin huu ich cho viec quan ly rong bien va TVTS trong ao nuoi thich

\\qp, gop phan phat trien mo hmh nuoi tom QCCT b^n vung tr DBSCL.

2 . PHUONG PHAP NGHBU CUU 2.1.'Hiu thap s6li§u

Danh gia vai tro va anh huong cua rong bien va TVTS trong ao nuoi torn QCCT duoc khao sat tai xa Thanh Tiing va xa Tan Duy('t thuoc huyen Dam Doi, linh Ca Mau tir thang 10/2018 den thang 4/2019. Cac ho nuoi torn QCCT duoc chon phong van chia thanh 3 nhom vc tinh tiang rong bien va TVTS xuat hien tu nhi^n trong ao gom (Nhom 1) ao nuoi tom QCCT co sir hi^n di^n tii nhien ciia nhieu loai rong bien va TVTS nhung khong co rong cau (rong h6n hgp), (Nhom 2) ao nuoi tom QCCT co rong cau xuait hien tu nhi^n uu the hon cac loai rong bi^n va TVTS khac va (Nhom 3) ao nuoi torn QCCT khong cd su hien di^n cua rong bien va TVTS nhung co su hicn dien cua cay duoc ho$c cay main chiem tir 20-30% dien tich ao.

Thong tin dugc thu thiip bang each phong van true tifip tir cac n6ng hp qua bang cau hoi soan san gom 90 nong hg nuoi torn QCCT, trong do 30 hg co rong cau. 30 ho co rong khac va 30 ho khong co rong. Cac bien chii yeu trong khao sat bao gom: (1) cac y^u t6 lien quan ky thuat nhu dien tich ao nuoi va muong bao. cham sdc quan ly, con giong, thudc, hoa ch^t; (2) cac tiiong tui lien quan den vai tro va tac dgng ciia rong bi^n va TVTS trong ao nuoi tom QCCl. miia vu xuat hien. phuang phap quan ly va loai rong mong muon dugc duy tri trong ao nuoi,...

(3) thong tin hieu qua tai chinh g6m chi phi, thu nhap, gia ban va loi nhu&n.

2.2.Xu!ysdUeu

So lieu thu thap dugc phan tich bang chuang trinh Excel va SPSS 16.0 va dugc trinh bay bang thong ke mo ta (trung binh ± do I?ch chuan). So sanh su khac biel v^ nang suat thu hoach, hieu qua

tai chinh giua cac nhom bang phan tich phuong sai mgt nhan to . \ . \ 0 \ A vdi phep thu Turkey (p<0.05).

3. KET QUA VA THAO LUAN

3.1. Thdng tin ky tfau^t trong ao nu6i t6m QCCT Cac thong sd ky thuat trong mo hinh nuoi tom QCCT a huyen Ddm Doi, tinh Ca Mau dugv trinh bay trong bang 1. Ket qua khao sat cho thjiy c:\u true ao nuoi tom QCCT ciia 3 nhom khong ch^nh lech nhieu. bao gom dien tich nuoi, chi^u rgng muong bao. ti Ie muong bao va ti le mat trang ao dao dgng lan luot la 2.0-2.9 ha, 2.5-2.8 m, 25,2-28,2% va 71.8- 74,8%. Do sau muong bao trung binh 1,25-1,34 m va muc nuac trang la 0,55-0,61 m.

Theo Tran Nggc Hai va Nguydn Thanh Phuang (2009), muong bao cd vai trd quan trong trong ao nuoi tom QCCT nhu la noi tni an cho torn, cua, ca trong ao nuoi. dac biet vao miia khd nhi^t dd tren mat trang ao tang cao vao giua tnra. ti 1? muong bao 25-30% la phii hop va muc nudc tren trang phai Idn han 50 cm nham tranh cac anh hudng bat Igi nhu bien ddng nhiet do ngay dem va han ch^ anh sang xam nhap den n^n day ao (Tran Nggc Hai va Nguyen Thanh Phuang, 2009). Qua dd cho thay cac ao nuoi tom QCCT dugc thiet k^ cd ti 1? di^n tich mat trang ao rdng va duy tn muc nudc thich hop la di^u ki?n thuan loi cho rong va TVTS phat tn^n Oaikumar, et al., 2011: Hurd et al., 2014; Nguyen Thi Nggc Anh, 2015).

Cac hg dugc khao sat d^u thuc hi^n cai tao ao 1 lan/nam va da s6 (70-90%) hd khong sii dung hda chat, sd cdn lai (3,3-20% nong hg) sir dung day thudc ca, voi. zeolite hoac phan vd co (NPK, DAP) trong cai tao ao. Mo hinh nudi torn QCCT, tat ca cac hg nuoi tom k^t hop vdi cua nham tan dung dien tich mat nudc va tAng thu nhap. trong dd tdm su la ddi tuong nuoi chinh. mat do tha tdm dao dgng 4,0-5,3 con/mVlan vdi sd lan tha la 8,0- 9.3 lan/nam. Cua bien dugc tha vdi mat dp 0,05-0,08 con/mVlan va sd lan tha trung binh 7,5+3.3 lan/nam.

Ve quan ly ao, cac ao nudi tdm QCCT dugc thay nudc 2 lan/thang vao cac ky tneu cuong, mdi dot thay tir 36.341,3%. Thdi gian bat dau thu tia tdm sau 3,84.2 thang nudi vdi kich ca tdm dao dgng 44,244,9 g/con (tnmg binh 43.7+11.0 g/con). Theo nhan dinh cua Tran Ngoc Hai va Nguyfin Thanh Phuang (2009). nuoi tdm theo hinh thuc QCCT la mo hmh nudi tdm d mat do thap dao ddng 1-5 con/m^ thuong khdng vuot qua 7 con/m^ ddi vdi tdm va khdng vugt NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 11/2019 ¹¹⁷

KHOA H p c CONG NGHE

qua 1 con/m- doi voi cua bien. Nhm chung, kfit qua Thoi Binh, tinh Ca Man cua \'o Nam Son va ( khao sal nay tuong ddng vai kfit qua khao sat dac (2018).

diem ky thuat cua md hinh nudi torn QCCT d huyfin

Chi tifiu Cau tnic ao nuoi Di^n tich ao (ha) Chieu rgng muong (m) Ty lfi muong bao (%) Ty lfi mat trang (%) Do sau muong bao (m) Muc nudx: trang (m) Thdng tin ky thuat Cai tao ao Oan/nam) Thudc, hda chat:

Day thudc ca (%) Zeolite (%) Voi (%) Phan NPK, DAP (%) Khong su dung (%) Mat dd tha tdm (con/m-/lan) Mat dd tha cua (con/mVldn) Sd lan tha tdm Oan/nam) So ian tha cua G&n/nam) Thay nudc G^/thang) Luong nuoe thay (%/lan) Thai gian bat dau thu tia tom (thang) Kich CO tdm sii thu hoach (g/con)

Rong h6n hop (Nhom 1)

2.3+0,,'i 2,7±0,6 25,2-i-7,0 74,tii7,0 1,26+0.27 0,55±O,25 1 0 0 10 0 90 4.1+2.1 0,05±0.n4 9.3+2,9 7,9±4.5 2 36.3+14,1 4,1+0,7 43,4±11,0

Rong cau (Nhom 2)

2,0+1,1 2.8+0,8 28,2+7,7 71,8±7,7 1,25+0,37 0,58+0,19 1 3,3 10 10 0 80 5,3±4.0 0.05+0,03 8,8±2,6 6,8±2,6 2 41.3±15,5 3,8±0,7 44,9+11,2

Khong rong bien vaTVTS (Nhom 3)

2,i>+l,2 2,5±i),.-i 27.7±5,2 72.3±5,2 l,:!l±l>.29 0,(;i±(l,37 1 0 10 20 6.7 70 4.0+2.4 0,08±0,05 8,0±2.7 7.6±2,2 2 37.7+17,4 4,2+0,7 42,9+10,7

Trung binh (n-M)

2.4±1.1 ' IW),7 l j n \ 0 ± ( i 8 _

73,0+6,8 _ U S ± a 3 1 _

1 1,1 ±1.9 6.7±5.8 13.3±5.8 2.2±3.9 80+10 3.9±1.5 0,06+0.04 8,7+2.7 7,5+3,3 2 38,4±15,7 4,0+0,7 43,7+11,0 3.2. Thdng tin v^ rong bi^n v^ TVTS hi^n di§n t}f

nhifin trong ao nudi tdm QCCT

Tiiong tin tir cac nong hd cho bifit co 4 loai rong bifin va 3 loai TVTS xuat hien tu nhifin quanh nam irong ao nuoi tom QCCT. Trong 4 loai rong bien cd 76.7% sd hg cho rang rong men Cladophoraceae (rong xanh). ke den la rong can Gracilana (65,0% so hg), rong biin Enteromorpha (43,3% sd hd) va rong nhdl Spirogyra (6,7% sd ho); 3 loai TVTS gdm rong da A.7/.7S- (30.0% so hd). rong duoi chdn Ceiatophyllum (15,0% so hg) va cd nan Eleocbaris (16.7%) thudng hien dien tu nhien trong ao nudi tdm QCCT (Bang 2). Tlieni vao do. co 48% so ho nhan thay trong ao nudi tdm QCCT thuong cd 3 loai rong/T\TS. 42% sd hd nhan thay cu hai loai rong/'lATS va 10% so hd cho rang thudng cd 4 loai rong/T\TS. Cac loai rong va T\TS cimg hifin difin

va phat trien df mot thoi diem hoac xuat hien luan phien nhau trong nam nhir rong xanh vm rong nhot, TVST (rong da), rong xanh voi rong cau va rong bun, rong bun, rong da vdi cd nan, rong duoi chdn, rong da, rong nhdt. Tuang tu, khao sat cua du an 1TB- Vietnam (2011) va Nguyfin Thi Ngoc Anh (2015) cho bifit cac loai rong bien va TVTS xuat hifin ddng thdi hoac chung phat trien xen ke ndi tiep nhau trong cac thuy vuc nudc Ig.

Tir ket qua khao sat cd 86,7% y kien cua nong hd cho bi^t rong xanh (rong men) phat tnen nhifiu nhat trong ao nuoi tdm QCCT tu thang 3 den thang 8 hang nam vdi khoang do man va mirc nuoe Uiich hop la 15-35%o va 0,1-0.4 m. Kr/ , au iihat tnen tdt nhat tir thang 8 den thang 4 nam sau i, do man 12-25%o va muc nudc 0,2-0,5 m (65,0% nong ho). Rong biin hien didn nhifiu nhat tir thang 11 dfin thang 3 nam sau 6

IIS NONG NGHIEP VA PHATTRIEN NONG THON - KY 1 -THANG II/2019

KHOA HOC CdNG NGHE

dg man 12-25'W va muc nuirt 0^-0.4 m (56,7% ndng hg).

Cac nong hg khac cho rang rong nhdt (55% ndng hd). rong da (63,3% nong hg), rong dudi chdn (51,7%

ndng hd) va cd nan (58.5% nong hg) xuat hien tu

B4ng 2. Y ki^n ndng hO vk cdc loM rong bi^n vd TVTS trong ao nudi tdm QCCT va d i ^ ki$n mdi trudng va miia vu thich hgp cho syi phat tri^n cua chiing (n = 60)

nhien va phat trifin nhieu nhat irong ao nudi lom QCCT tir thang 6 dfin thang 10 vai dd man dao dgng 2-10%o va miic nuoe 0,3-0,7 m. Do trong thich hgp cho cac loai rong va TA'l'S tir 0,3 m trd Ifin.

Logi rong bi^n va 'r\"I"S

V ki^n nong ho(9S)*

Do ni$n (%o) Miic nubc (m) Dg trong (m) Thang (dl) ron Thang 3-8 Thang 84 Thang 10-3 Thang 6-10

Rong bien ' Rong xanh

(Cladophoraceae,

76,7 15-35 0,1-0,4 0,4-0,6

Rong cau {Gracilana)

Rong biin {Enterom orpha)

Rong nhot {Spirogyra)

Rong da {Najas)

65,0 1 43,3 16.7 30.0 12-25 1 12-25

0,2-0,5 0,2-0,4 0,3^,5

3-10 , 2-10 0,30,5 0,3-0.6 0,3^.5 1 0,4-0,5 0.4O.6 g bicn va thuc vat thiiy sinh phat trien nhieu (% y kien nong ho)

86,7

75.0 56,7

55.0 63.3

Thuc vat thiiy smh Rong duoi chon (Ceratopli.vlluin)

15,0 2-10 0,3-0.6 0,4-0.6

51,7

Co nan {Eleochansi

18,3 2-10 0,3-0,7 0,4-0,6

58,5

" Ykien nong ho ve vf cac loai rong bien va Tl'TS Cac nghien cuu trudc bao cao rang su phat tri^n va phan bd cua rong bien va TVTS bi anh hudng bdi cac yeu td mdi trudng nhu cudng do anh sang, do trong, dd man. nhifit dd va chail dinh duong trong thiiy vuc. Trong dd nhie! dp va dd man la hai nhan td chinh anh hudng den sinh tnidng, hinh tliai ciia rong bifin. phan bo dia ly, sir thay ddi sinh trudng theo miia vu, su bifin ddng ciia cjiu true quan xa rong bien theo miia vu va mdi loai rong bicn va TVTS cd khoiing dp man va nhiet dd tdi iru cho sinh trudng va phat tnfin Oaikumar, et al, 2011; Mukund, et al., 2012; Hurd et al, 2014. Vaheeda va Thara. 2014:

O'Hare, e^a/.20ia).

Khao sat cua Nguyfin Thi Ngoc Anh (2015) da tim thay rong luc {Enteromorpha spp. va Cladophoraceae) va thuc vat thiiy sinh {.\ajas spp.) a ao nuoi thiiy san QCCT va thiiy vuc tu nhifin ciia tinh Bac Ueu va Sdc Trang cd sinh luong kha cao va bien ddng lon trong thdi gian khao sat. Nhifit dd va do man la hai nhan td chinh anh hudng nhifiu den sinh lugng va phat tnen cua rong luc va thuc vat ihuy

tiiudnghien difn tu nhifn trong ao nuoi torn QCCT sinh. Rong biin it xuat hifin vao miia nang ndng khi nhiel do cao hon 35''C. cac loai rong men thuoc hg Cladophoraceae xuat hien gdn nhu quanh nam va phat trien tot d difiu kifin nhifit dd va do man cao.

Thuc vat thuy smh {Najasspp) phat tnen manh vao miia mua d thiiy vuc cd do man thap va dd trong cao.

Tuong tu, nghien cim gan day cho biet cac loai rong xanh thudc ho Cladophoraceae phat tnen cai quan vao cac loai rong khac: Enteromorpha spp. (rong biin), Spyrogyra Ionia (rong nhdt), Gracilana sp.

(rong cau), Chara baltica (rong hoi) trong cac thiiy vuc nuac la a tinh Bac Dfiu va Ca Mau. Bifin ddng cac loai rong nay phu Ihudc vao do man, rong xanh thudng phan bd chii yfiu d cac thiiy vuc cd dd man tu 5 den SO^x., xuat hifin nhifiu loai rong xanh nhir Cladophora crispula, Chaelomorpha linum, Phizoclonmin kemeri, Rhlzoclonium kochianum. Khi cac thiiy vuc cd dd man giam xudng l-2%o do mua nhieu thi sinh khdi rong xanh giam chi con mdt vai loai. ddng thdi xuat hien cac loai rong khac nhu rong bun. rong Iam va rong hdi (Nguyfin Thi NJ^CJC Anh va (•n..2018).

NONG NGHIEP VA PHATTRIEN NONG THON - KY 1 - THANG 11/2019 ¹¹⁹

KHOA HQC C 6 N G N 0 H »

3.3. Thdng tin v^ vai trd, tdc h^i va quan Iy rong bi^n vA TVTS trong ao nudi tdm QCCT

3.3.1. V;iI tro cua rong bidn va TMS Da sd nong hd duoc khao sal cho rang rong bifin va TVTS giiip cai thien chat luong nuoe trong ao nudi torn QCCT (91.7% sd hd). ddng thoi lam thiic an true tiep cho ca, tdm va cua (85.0% so ho) va la noi tni an cho ca, tdm va cua (81,7% sd hd), hoac tao ngudn thiic an tu nhien cho ca, tdm va cua (53,3% sd hd), mdt sd it hp (3,3% sd hp) sii dung rong bien va TVTS lam thirc an bd sung cho gia sue nhu heo. ga, vit

(Bang 3). Y kifin cua ndng hd phii hgp voi kfil qua cua cac nghifin cim trudc, rong bifin v.i HT^ '^^

nhifiu vai hd rat quan trong trong ^--u limy ^"^^ ''^' man nhu mn cu tni. tao ngudn thue an tu nhien phong phu, vudn ucmi nudi au triing va smh san cho ddng vat thuy san. cd kha nang hap thu manh cac chat dinh duong trong mdi trudng giiip cai thien chat lugmg nmJc va can bang hfi sinh Uiai (Dnih Thi Phuong Anh va Hoang Thi N.t:<ic Hifiu, 2010;

Jaikumar, eA a/.. 2011; Hurd, e/a/, 2014. Vaheeda. va Simon 2014; O'Hare. et al., 2018)

B ^ 1. Vai trd Y klfin ndng hd (%) 2. Tac hgi

Y kifin ndng hp (%)

3. Bifin phap quan ly Y ki^n ndng ho (%) 4. Loai rong ua thich Y kien nong hd (%)

3. Vai trd, tic hai Cai thifin chat

lugng nuoe 91,7 Lam nuoe ao rat

trong 45,0 Cai tao ao+ miic nude sau +gay

mau nudc 71.7 Rong cau

35,0

ir^ quin ty rong bi&i vd TVTS trong ao nudi tdm QCCT Thirc an true tifip

cho ca. tdm, cua 85,0 Gay thdi nuac khi

tan lui 56,7

Nm tni an cho ca.

torn, cua 81,7 Can trd hoat ddng sdng ciia

tdm, cua 58,3 Dinhkyvotbd ,.. , , , , .•

. , ,, 1 Sudung hoa chat mgt phan

91,7 Rong biin

16,7

53,3 Rong xanh

6,7

Tao ngudn thiie an tu nhifin cho ca, lom, cua

:')3.3 Giam tang trudng va nSng

suait tom 73,3 Tha ca an thuc

vat 35,0 Rong da

23,3

Thiic an bo sung cho gia

siic 3,3 Khdng gay hai

21,7

Khdng tac ddng 8,3 Cdnan

18,3 khac nhan thay rong bifin cimg vdi thuc vat thiiy sinh deu cd vai trd tich cue trong thiiy vuc, tuy nhifin khi chiing phat tri^n cue dai se gay thifiu oxy vc dem va mdi trudng ao nudi bien ddng ldn. Khi chiing tan lui gay ra nhifiu tac hai nhu d nhifim ao nuoi, phdng thich ra nhieu khi ddc (H^S, .N'Hi...) gay hat cho tdm, ca trong ao nudi hoac cd the dan dfin chfit hang loat (Durborowe/a/.,2007).

3.3.3. Bien phap guan ly rong bien va TVTS De han chfi rong bi^n va TVTS phal trien qua miic trong ao nudi tdm QCCT, 71,7% so hd cho biet hang nam cai tao ao ky ket hop gay mau nuoe va giu miic nudc trang sau (>0,5 m). Da sd hp (91.7%) chon bien phap dinh ky vdt bd mgt phan rong bi^n va TVTS khi chiing phat tnen khoang •tfi-TiCfH, mat h-ang ao. su dung hda chat (thudc difit lao, BKC...) djet rong (53,3% sd hd). Tuy nhifin. mpt sd it ho (83%) c6 y kifin la khdng tac ddng khi rong bien va TVTS phat tnen nhi^u do cac hd nay chi cd rong cau va rong da NONG NGHIEP VA PHATTRIEN NONG THON - KY 1 -THANG n/2019 3.3.2. Tac hai ciia rong bien vaTlTS

Khi rong bi^n va TVTS phat trien qua miic, chung gay ra mot sd tac hai cho ao nudi tdm QCCT nhu lam nudc ao rat trong (45.0% sd ho), gay thdi nudc vao thdi diem tan lui (56,7% sd hd), han che khdng gian sdng va can trd hoat ddng ciia tom. cua (58,3% sd hd). Tir dd lam giam tang trudng va nang su;il tom nudi (73,3% so hd). Tuy nhien, cd 21,7% sd hp cho rang rong bien va T\TS khdng gay hai cho ao nudi tdm QCCT (Bang 3). Theo bao cao cua du an ITB-Vietnam (2011) cho biet. rong bien va TVTS trong ao nudi torn QCCT dong vai trd la ngudn thiic an tu nhifin cho tdm cung nhu dn dinh su bifin ddng ciia nhifit dd vao miia khd. Tuy nhifin khi chiing phat trifin qua miic co the se lam giam difin tich cho dong vat day phat tnen, han chfi anh sang va canh tranh sir dung cac mudi dinh dudng vdi phifiu sinh vat phu du, dac bifit la tao trong ao nudi, dieu nay cd the dua dfin su thifiu hut thiic an tu nhifin trong ao. Nghifin ciiu 120

KHOA HOC CONG NGHE

xuat hifin luan phien trong nSm khdng gay anh hudng xau dfin ao nudi (Bang 3). Nghien cuu su ki^m soat thue vat thiiy smh, rong soi va tao trong ao nudi thiiy san cua Durborow, et al. (2007) cho rang quan ly rong soi, tao va T \ T S trong ao nudi thuy san vdi chi phi hop ly va than thifin vdi mdi trudng phu thudc vao rat nhifiu yeu td nhu loai thuc vat, miic dd phat tnen, loai va giai doan phat tnen ciia ca hay giap xac trong ao, chat lugng nudc, thoi gian trong nam va thcri ti^t. Hi^u dugc su tuang tac cac yeu td nay can cd kinh nghifim thuc tifin de ap dung cac bien phap khac nhau trong ki^m soat su phat tri^n TVTS, rong tao trong ao. Bifin phap hda hoc la each nhanh nhat, tuy nhifin, chat lugng nude ao nuoi trd nfin xau di do xac rong tao chet phan htiy. Hon niia, mdt sd loai hda chat cd the tdn luu d day ao gay ddc trong thdi gian dai va mdi loai hda ch^t cd hifiu qua cho timg loai thuc vat. Vi the, phdng ngira la bifin phap thich hap hon doi vdi quan ly TVTS. Thfim vao dd, nhdm nghifin ciiu chi ra rang kiem soat su phat tnen ciia TVTS va cac loai rong sgi trong ao thuy san nfin ket hgp nhifiu bifin phap: bifin phap vat ly (thu dgn bd rong ra khdi ao nudi. phoi day ao va kfi tiep dang cao miic nude); hoac bifin phap sinh hgc: gay mau nudc nham tao dieu kifin thuan loi cho vi tao phat trien sfi uc che cac loai rong sgi va TVTS phat trien hoac nuoi kfit hgp vdi cac loai ca an thuc vat (ca trim cd, ca tai tugng, ca chep...). bien phap hda hpc duge khuyen cao chi thuc hien d khau cai tao ao.

3.3.4. Loai rong bifn va TVTS duoc ua tiiich nhat Theo y kien cua 60 ndng hg duoc khao sat, trong sd cac loai rong bien va TVTS hien difin tu nhien trong ao nudi tdm QCCT. rong cau duoc cac ndng hd mudn duy tri trong ao nudi tdm QCCT chifim ti Ifi cao nhat (35% so hd), kfi dfin la rong da (23.3% sd ho), cd nan (18,3% sd ho), rong bun (16.7%

sd hd) va rong xanh chi cd 6.7% sd hd muon duy tri Irong ao nudi. Tuong tu, kfit qua khao sat ao nudi tdm QCCT cua ndng hd d- DBSCL cua du an ITB- Viehiam (2011) cho thay mdt so loai rong bifin va TVTS nhu rong bun, rong xanh, rong da, cd nan la ngudn thiic an tu nhien tdt cho tdm va cai thien chat lupng nudc trong ao nudi, gdp phdn lam tang nang suat va thu nhap cho ndng hd. Rifing rong xanh sinh trudng nhanh va khd kiem soat su phat trien qua miic cua chung (Nguyfin Thi Ngoc Anh va ctw.

2017) nen rat it dugc ndng hd thich duy hi trong ao nudi. Rong cau la loai rong kinh le, la ngudn nguyen li^u de chifit xuat agar duge iing dung trong nhieu N O N G NGHIEP VA PHAT TRIEN NONG THON

Unh vuc, dac bifit rong cau co kha nang hap thu cac muoi dinh duong nhanh va vugrt nhu cau cho hoat ddng sdng (Lfi Nhu Hau va Nguyfin HCru Dai, 2010) va dugc sir dung nudi ket hgp hay luan canh giup giam chl phi thiic an va cai thifin moi trudng trong cac mo hinh nudi trdng thuy san bfin vung (Yang et al., 2015; Andayani, et al, 2016, Fourooghifard, et al., 2018; Nguyen Thi Ngoc Anh etal., 2018). \'i the rong cau dugc nhieu nong hd ua thich duy tri trong ao nuoi tom QCCT.

3.4. Cac y^u td tAi chinh cua md hinh nudi tdm s u Q C C r

Nang suat Ket qua khao sat cho thay, ao nudi tdm QCCT d- nhdm 2 cd rong cau dat nang suat tdm su trung binh 336.8 kg/ha/nam. cao ban nhdm 1 (rong hdn hop khong cd rong cau 282,1 kg/ha/nam) nhung khong khac bifit thdng ke (p>0.05). ca hai nhdm nay cd gia tri cao hon cd y nghia thdng kfi (p<0,05) so vdi nhdm 3 (ao khdng cd rong bi^n va TVTS) vdi nang sual 107,7 kg/ha/nam. Tuy nhifin, nang suat tdm tu nhien (28,5 va 24,7 kg/ha/nam) va cua bien (56,7 va 42.4 kg/ha/nam) d nhdm 1 va nhdm 2 thu dugc thap han cd y nghia thdng kfi (p<0,05) so vdi nhdm 3 (97,0 va 114,6 kg/ha/nam), theo thiitu (Bang 5).

Gia ban: Bang 4 cho thay gia ban tdm su trung binh d nhdm 2 cao nhat (230,0 ngan ddng/kg), kfi den la nhdm 1 ( 220,7 ngan dong/kg) va thap nhal la nhdm 3 (217,3 ngan ddng/kg). Tdm tu nhifin dba nhdm cd gia ban trung binh 52,7-62,3 ngan dong/kg. Cua bien cd gia ban 221.7-241,0 ngan ddng/kg. Theo thong tin ndng ho cho biet gia ban tdm, cua khac nhau theo kich ca, tom va cua cd khdi luang lon thi cd gia cao han va phu thugc vao gia thl trudng d timg thdi diem, cua gach cd gia cao hon g£Lp 2 lan cua thil,

Tdng chi, tong thu va lpi nhuan: Nhdm 1 va 2 cd tong chi tuong tu nhau (p>0,05), trung binh 18,7-18,9 trifiu ddng/ha/nam, cao hon cd y nghia thdng kfi (p<0,05) so vdi nhdm 1 (15,2 trifiu ddng/ha/nSm).

Nhdm 2 cd tdng thu va Igi nhuan tuong iing la 89,1 va 70,2 trifiu ddng/ha/nam, cao han nhdm 1 (76,7 va 57,8 trifiu ddng/ha/nam), tuy nhifin su khac bi^t khdng cd y nghia thdng kfi (p>0,05). Nhdm 3 cd tdng thu va lpi nhuan (54,1 va 39,0 trifiu ddng/ha/nam) thap hon co y nghia thdng ke (p<0,05) so vcri hai nhdm cdn Iai. Ket qua khao sat nay, cac nong hg dat tdng thu va Igi nhuan tu ao nudi tdm QCCT thap hon cac ndng hd dupc khao sat bdi Vo Nam Scm va ctv.

- K Y I - T H A N G l l / 2 0 1 9 121

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(2018), tdng thu va lpi nhuan trung binh Ian luot la QCCT d huyfin Thoi Bmh, tinh Ca Mau 107,1 va 93,8 trifiu ddng/ha/nam ddi voi ao nudi tdm

uQCCT

Chi U«u Rong h6n hop

(Nhom 1. n=30)

Rong cau (Nhom 2. n-30)

Khong rong bi^n vaTVTS (Nhdm

3. n=30)

Trung bmh (n.90) Nang suat san pham thu hoach (kg/ha/nam)

Tom sii Tom hr nhien

282.i±i::.2' 28.5±8.9' Cua bi^n \ 56,7±23.9' Gia ban (1000 d6ng/kg)

Tom sii Tom tu nhien Cua bien

!3(i.S+92.7"

24.7±I3,5"

42.4+10.7'

220.7±39.2 52.7±8.3 235.8±38.5

2.10.0+34.5 62.2+11.6 241.0+34.6

I07.7tt2' 97.0+16,S"

I14.6±49.5'

2I7.3±33.6 62..1±S 5 221.7+36.6

:4:.:±i33.7 511+40 6 'I.:±44.S

, A m7+1\S

.59.1+10,5 2.12.8+17.1 Hieu qua tai chinh (dneu d6ng/ha/nani)

Chi phi CO dinh Chi phi bi^n doi Tong chi Tong thu L<n nhuan

4,8±1.3 14.l±:..?

18,7*2.6"

76,7+29,1' 57.8+29.0"

3.7±1.3 15.2+3.5 18.9+3.7' 89.1*25.2' 70.2+26.4'

3.1+0.9 I2,l±3.1 i5.2±^.y 54.1 + 17.6' 39.0±17.l'

3.9±1.2 13.8+3.0 17.7±3.1 7.1..1+33.4 55.7+31.5 Cac gia tid (TB±DLC) ti-ong ciing mot hang co chu cai khac nhau thi khac biet co y nghia thdng kf (p<0,05)

Do phli rong bien va TVTS 0%*

< 50% (38.5+10.6%)

> 50% ((59.7±10.5%) S6miu

(n) n = 30 n - 3 4 n = 26

Nang Tom sii

107.7+42.0"

346.9+96.9' 284.4+114.0'

suat (kg/ha/nam) Tom tu nhien

97.0+36.8' 28.3+14.5"

25.4+9.0'

Cua bien 114.6±49.5'

44.6±14.8' 52.8+22.0'

Loi nhuan (tneu d/ha/nam)

39,0+17. 1' 72,68±28.3I"

58,28+26.98' 'Ao nudi tdm QCCT khong cd rong vi TVTS xuit hien ttr nhien, chi cd su hien dien ciia cay dudc hoac cay mdm trong ao nudi duoc xem la do phu 0%.

Cac gia tii (TB±DLC) tivng cung mot cot cd chu cai khac nhau thi khac biet cdy nghia Uidngke (p<0,05) Ket qua tren cho thJy ao nuoi tom Q.C.CY co chinh thong vcri bien chiia luong phii sa lon chay rong bien va TVTS hien dien trong ao nuoi thu duoc true hep vao ao QCCT nen nuoe riit due, nuoe moi nang suat va loa nhuan cao hon nhiiu so vcri ao lay vao ao co do b'ong rat diap (khoang 10-15 cm) khong CO rong Difu nay khang dinh vai tro tich arc nen chiing khong the phat trien va ton tai. Ddi voi ciia rong biin va TATS hien dien trong ao nuoi tom rong bien (Hurd, et al, 2014) va thuc vat thuy sinh QCCT giup nang cao nang suat va thu nhap ciia Oaikumar, et al, 2011), do trong thich hop cho nong ho da duoc ik cap 6 muc 3.3. Ngoai ra, qua chiing phat trien Ki 30 cm uir liin, neu thiiy vuc co khao sat thuc te va thong tm tir nong hp duoc biet do trong nho hon 20 cm ,. ' ,;i du- su quang hop ao nuoi tom QCCT khong CO rong bien va TVTS ciia rong bien va duy tn trong ihin gian dai rong phat men ty nhien la do nhiing ao nay thuoc khu bien va TVTS se bi tan lui, Thay vao do cac nong ho vuc gan bien, nuoe duoc lay vao ao QCCT qua kenh trong thim cay duoc va cay mam tao nguon thiic an 122 N O N G NGHIEP VA PHAT TRIEN N O N G THON - KY 1 - THANG 11/2019

KHOA HOC CdNG N G H t

tu nhifin va Iam nen cu tni cho tdm va cua. Cac difiu klfin nay phii hgp cho su phat trien cua tdm tu nhifin va cua bifin nhung co the la difiu kifin khdng tdi uu cho tdm su tha nudi cd ngudn gdc tir san xuat gidng nhan tao dan dein nang suat tdm thap hon ao cd rong bifin va TVTS. Ddi vdi ao nudi tdm QCCT, tdm su la ddi tugng nudi chinh nhung nang suat tdm su dat thap dan den Igi nhuan hi giam.

Bang 5 cho thay ti Ifi dp phu cua rong bien va TVTS trong ao nuoi tdm QCCT anh hudng rat lon den nang suat va Igi nhuan cua ndng hd. Nang suat tdm su trung binh b do phu tir <50% dat cao nhat (346,9 kg/ha/nam) kfi ddn la do phu >50% (284,4 kg/ha/nam) va do phu 0% dat thap nhat (113,5 kg/ha/nSm) va khac biet cd y nghia thdng kfi (p<0,05) giiira ba ti Ifi dp phii. Tuy nhifin. nang suat tdm tu nhien va cua bien d hai dd phu <50% va >50%

tuong tu nhau (p>0,05), dao dong ldn Iuat la 25.4-28,3 kg/ha/nam va 44,6-52,8 kg/ha/nam, thap hon cd y nghia thdng kfi (p<0,05) so vdi nhdm do phu 0% (tdm tu nhien: 99,6 kg/ha/nam va cua bifin 115,4 kg/ha/nam). Lgi nhuan khac nhau cd y nghia thdng ke (p<0,05) giira ba ti le dd phii, trong dd ao nudi tom QCCT cd ti lfi dp phu <50% la cao nhat (72,68 tneu d/ha/nam), kfi tifip la do phu >50% (58,28 tneu d/ha/nam) va th^p nhat la dd phii 0% (39,68 trifiu d/ha/nam).

K^t qua dieu tra ve su xuat hifin va tac ddng ciia cac loai rong bien trong ao nudi tdm QCCT d cac tinh ven bifin DBSCL ciia du an ITB-Vietnam (2011), hau hfit cac ho dan cd nhan dinh tuong tu, khi rong bien va TVTS xuat hifin vdi dd phu khoang 30-50%

difin tich ao nudi tdm QCCT thi cd lgi cho ao nudi va mdi trudng dn dinh. Nguoc lai, khi rong bien va TVTS phat trifin nhieu hon lam giam khdng gian sdng, gay bifin ddng mdi trudng ngay dem va d nhifim ngudn nuoe khi chung tan lui dkn den sinh trudng va nang suat tdm bi giam. Nghifin cuu cua Nguyfin Thi Ngoc Anh va ctv. (2017) nhan thay khi ao nudi tdm QCCT cd dd phu rong <50% giiip dn dinh mdi tnrdng va nang cao nang suat tdm nudi. Tuy nhien khi do phu rong >50%, ham luong oxy hda tan va pH bifin ddng Idn trong ngay va dd trong cao, khi rong tan lui, ham luong TAN. NO., H.S tang len rgit cao va thudng gay hai tdm nudi dan dfin nang suat va thu nhap cua ndng hd bi giam. Tuong hr. khao sat cua Vo Nam Son va ctv. (2018), ti le difin tich thuc vat trong ao nudi tdm QCCT <4ri% dat nang suat tdm cao hon so vdi nhdm cd ti lfi thuc vat >45% va cac nhdm

cd ti lfi thuc vat <60% cho lpi nhuan cao hon co y nghia so voi nhom cd ti lfi thuc vat >60%.

4 . KFT LUAN VA KEN NGHI

Rong bien va thuc vat thuy sinh dong vai trd quan trong trong ao nudi tdm QCCT nhu cai thifin chat luang mroc. cung cap thuc an true tiep, lam noi tru an va tao ngudn thirc an tu nhifin cho tdm, cua, ca. Ben canh dd, chung ciing gay ra mdt sd trd ngai nhat dinh nhu lam nudc qua trong, gay thdi nuoe khi tan lui, can trd hoat ddng sdng cua tdm, cua va lain giam nang suat tdm nudi khi chung phat tri^n qua miic.

Trong cac loai rong bien va thuc vat thuy sinh thi rong cau dugc nhieu ndng hg ua thich (35,0%). k^

den la rong da (23,3%), cd nan (18,3%), rong bun (16,7%) va rong xanh (6,7%).

Ao nuoi tdm QCCT cd rong cau hifin difin uu thfi hon cac loai rong bien va TVTS khac dat nang suat torn su (336,8 kg/ha/nam) va lgi nhuan (70,2 tnfiu ddng/ha/nam) cao nhat, ke den la ao cd rong hdn hgp va TVTS dat 282,1 kg/ha/nam va 57,8 trieu/ha/nam va thap nhat la ao khdng cd rong bi^n va TVTS chi thu duoc 107,7 kg/ha/nam va 39,0 trifiu/ha/nam

Ao nudi tdm QCCT duy tri dd phu rong bi^n va TVTS <50% thu dugc nang suat tdm sii va loi nhuan cao hon ao cd dd phu >50% va ao khdng cd rong biln vaT\TS

Nghien cuu nudi trdng rong cau trong ao nudi tdm QCCT lajn co scr khoa hgc va thuc tifin dfi khuyfin khich phat trien nudi trdng va iing dung loai rong nay d ddng bang sdng Ciiu Long.

LOI CAM ON

De tai nay thuoc Chuong trinh Cong nghe Nuoi trdng Thtiy san xanh "Green Technology Inovation for Aquaculture" F-2-0DA dugc tai tra bdi Du an Nang cap Tnrong Dai hgc Can Thu IN 14-P6 bang nguon vdn vay ODA tii Chinh phu Nhat Ban. Nhom tac gia .xm chan thanh cam on cac nong ho a tinh Ca Mau da sdn long cung cap thong tin thuc te vf ao nuoi torn su quang canh cai tien. Xm cam on em Dinh Thanh Hong va NguySn Thi Van Thi da hd tru trong thai gian thuc hien khao sat.

TAI LEU THAM KHAO

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KHOA HOC C 6 M « NGHt

verucosa) to increase production of \'annamei shnmp in traditional pond district Bangil-Pasuruan.

Research Journal of Life Science 3,16-22.

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B. I. Onder. R. J. and Minis. S. D., 2007. Aquatic weed control in ponds. Kentucky State University Kentucky State Umversity Aquaculture Program, a KSUL and Grant Program, 24 pp.

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NONG NGHIEP VA PHATTRIEN NONG THON - KY 1 -THANG 11/2019

KHOA HOC CONG NGHE

INVESTIGATING THE ROLE OF SEAWEEDS AND AQUATIC PLANTS IN THE IMPROVED - EXTENSIVE SHRIMP FARMS FROM DAM DOI DISTOICT, CA MAU PROVINCE

Nguyen TTii Ngoc Anh, Nguyen Hoang \^nh, Lam My Lan, Tran Ngoc Hai Summary

The survey was conducted by interviewing directly 90 farmers cultunng the tiger shnmp in ihe improved extensive farms QESF) from Dam Doi distnct, Ca Mau provuicc to assess their roles and impacts to the producbon and profit of this model. The householders who were selected for interviewing divided mto three groups depending on the existence status of seaweeds and aquatic plants m the lESF. Group 1: the lESF having natural occurrence of different seaweeds and aquaQc plants but absence of red seaweed (mixed macroalgae), group 2: the lESF having aatural occurrence of red seaweed, which dominates over the mixed macroalgae, and group 3: the lESF have no natural occurrence of seaweeds and aquatic plants but presence of the mangrove and Avicennia trees occupy about 20-30% of farm area. The surveyed results from the ideas of householders showed that there were 4 types of seaweeds (red seaweed Gracilana, green seaweed Cladophoraceae, gut weed Enteromorpha and sticky weed Spirogyra) and 3 types of aquaUc plants (slone weed Najas, foxtail weed Ceratophyllum and spike rushes EleochacR) developed naturally in the lESF.

Among them red seaweed has been most preferable (35.0% householder), followed by stone weed (23.3%

householder) and the remaining has been less desirable to maintain in the lESF. Most the ideas of the householders (81.7-91.7%) slated that seaweed and aquaUc plants play important roles in the lESF such as improvement of water quality, direct food, creaUng natural food and shelters for aquaUc organisms. Besides thai there was some negative effects namely clear water or water polluUon when they die off, hindenng the movement of shrimps and crabs which caused reduction of productivity in the farms (33 3-70.0%

householders). Croup 2 achieved the highest tiger shnmp production and profit (336.8±92.7 kg/ha/year and 70.2±26.4 million/ha/year), followed by group 1 (282.1+122 2 kg/ha/year and 57.8±29.0 million/ha/year). Tlie values of these two groups were significantly higher (p<0.05) than those in group 3 (107,7±42.0 kg/ha/year and 39 0±17.1 miUion/ha/year). Moreover, the lESF having coverage percentage of <50% obtained higher shnmp yield and profit compared to the one with coverage percentage of >50% and the lESF without the presence of seaweeds and aquatic plants.

Keywords: Improved- extensive shnmp farm, seaweeds, aquatic plants, coverage percentage, producUon, prodl.

Ngudi phAn bi^n: PGS.TS. Nguyen XuSn Ly Ngdy nh|nb^: 7/6/2019

Ngiy thdng qua p h ^ bi^n: 9/7/2019 Ngiy duyet dang: 16/7/2019

N O N G NGHIEP VA PHATTRIEN N O N G THON - KY 1 - THANG 11/2019 125