KHOA HOC CONG NGH$
IVGHIEIM CIJIJ D A C D I E M SIINIH HOC 5 I I V H s A l V CIJA IXIGAO D A U [Meretrix meretrij^ D VLJIMG CIJA DIEIM
T H U A I M A I V , T H I J A THIEIM - H U E
Nguydn Van HuyS Trin Vinh Phmmg^, Phan Tlii Thu Hong^
T6MTAT
Nghidn cuu diroc ti^n hanh de xac dinh mgt sd dac diem sinh hoc sinh san quan trong cua ngao dau lam co sd cho viec san xuat giong va nuoi thuong pham. Miu ngao dau duoc thu hang thang 30-50 con b viing gan cira bien Thuan An, thuoc ddm pha Tam Giang, hnh Thira Thien - Hue. Ket qua cho thay qua trinh phat tn^n tuy^n sinh due aia ngao dau b dam pha Tam Giang trai qua 5 giai doan gom: giai doan nghi, giai doan phat trien, giai doan chin muoi, giai doan sinh san va giai doan thoai hoa. Miia vu sinh san ciia ngao b viing dam pha Tam Giang bat dau cudi thang 4 den thang 8, de ro vao thang 5, thang 6. Kich thuoc thanh thuc sinh due lan dau cua ngao dau vimg dam pha Tam Giang a kich thudc 40 mm; ty le duc/cai vao miia smh san dao dong 0,9 - 1,1. Dp beo cua ngao dau dat 10,44 -19,83%; do beo cua ngao tang dan ttr thang 2 den thang 6; giam dan tir thang 7 den thang 1. Ngao dau thanh thuc vdi kich thudc chi^u dai tuong iing 40-69 mm; sue sinh san tuyet ddi trung binh dat 1.253.667 Ining/ca the; sire smh san tuong ddi dat trung binh 25.231 trung/gam.
Tu khda: Ngao dau, smh hgc sinh san, dam pha Tam Giang.
1 . DAT VAN DE
Ngao dau (Meretrix meretrix) la loai co gia tri thuong mai rat quan trgng thudc Idp hai manh vd va hien tai dang chiu ap luc khai thac ngudn Ipi tu nhien phuc vu nhu cau cua con ngudi (Liu va cs. 2006).
Cimg vdi nhiing tien bd trong ky thuat san xuat gidng, ngao dau da trd tiianh mdt trong nhiing loai hai manh vd nudi chu yeu b cac vimg bai tneu cua Trung Qudc (Tang va cs. 2006). Ngao dau cd kich thudc Idn len den 91 mm chieu dai, dat khdi lupng CCT the 230 g. Thit ngao rat tdt cho siic khde con ngudi.
Vd cua ngao cdn duoc su dung lam thu cdng my nghe (Nugranad, 1999). Ngao dau la loai an Ipc, sdng day CT khu vuc cua sdng, viing trieu cd day hi cat cho den day biin; ngao dau cd kha nang xir ly d nhidm chat hiiu co trong nude va cai thien didu kien trdm tich day.
Ngao dau la mdt trong nhiing ngudn lgi thuy san vimg dam pha Tam Giang - Cau Hai cd gia tri kinh te cao. Nudi tiiuong pham ngao dang duoc phat trien manh h-en pham vi ca nude, nhu cau con gidng ddi hoi cang nhieu, trong khi hai de tu nhien cua ngao
ngay cang thu hep, khai thac can kiet ngudn ngao bd me phuc vu nhu cau thuc pham cho con ngudi, vide san xuat gidng nhan tao chua dap ling du nhu cau gay ap luc rat Ion cho ngudn loi tu nhien dang ngay cang suy giam (Nguydn Thi Xuan Thu, 2005). Do vay, de dap ling vdi yen cau cap thiet trong nghien cuu khoa hoc ciing nhu cd the la budc khdi dau cho smh san nhan tao ngao gidng, tir do mo ra CCT hdi cung img cho nhu cau thi trudng cua ngudi nudi, co SCT dir heu ve smh hpc sinh san ciia ddi tuong nay la rat quan trpng can duoc nghien ctru day du.
2 . VAT UEU VA PHUONG PHAP NGHIEN CUU 2.1. Dia di^m va vat li§u nghidn ciiu
''*"•»• ( 9> '--^
1
Chu Ihfch ' • " l ' ^ '
~ •®'
Hinh 1. Khu vuc thu mlu nghidn ciiu ven cua bifo Thuan An
' Khoa Thuy san, Tmdng Dai hpc Nong Lam, Dai Hoc Hul
' Vien Cong nghe Sinh hoc, Dai hoc Hue ' Chi cue Thuy san tinh Thiia Thien - Hue
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 4/2019 69
KHOA HOC CONG NGHl
Nghien cuu duoc tien hanh tii thang 10/2017 thu hang thang 30-50 con tr6n quan dan ngao khai den thang 9/2018 tai Ijhu vuc gin cua bien Thuan thac, dam bao ty le cac nhom kich thuoc. Mot so An, thuoc dim pha Tam Giang, tinh Thira ThiSn - dac diem tai khu vuc thu miu dupe rao ta trong Hue (Hinh 1); noi co su phan bo Idia nhieu ngao hinh 1 va bang 1.
dau theo thoi gian trong nam. Miu ngao diu duoc Diem
N2 N3 N4 N5 N6 N7 N8
Ban/?
VI do 165604 165585 165631 165615 165601 105695 165570
1. s a c d i f a nfa day v4 mau mroc viiny nhan h6 neao Kinh do
1076305 1076311 1076281 1076253 1076231 1076199 1076357
Nen day Cat Cat Cat, it bim
Cat bim Cat bim Cat bim Cat bim
Due Due Due Vang xanh
Buc Xanh bien
Xanh 4u
Ghi chu Bai ngao Bai ngao Bai eitag, nhieu Bai Eiong, nliiiu Bai ngao, nhieu
Bai ngao Bai ngao 2.2. Phirong phap nghidn cuu
2.2.1. Phuong phap xac dhih cac giai doan phat trien tuyen sinh due
Nhiing ca the thanh thuc cd tuyen sinh due cang trdn va phat trien bao lay phan chan. Diing dao rach, tach tuyen sinh due va cd dinh trong dung dich formol 10% de cat miu md hpc, nhudm miu bang hematoxylm va eosin. Quan sat tidu ban bang kinh hien vi quang hoc 100-400 lan, md ta su phat trien cua tuydn sinh due, te bao sinh due theo thang 5 bac cua Braley (1988) va can cii vao tai Ueu cua (Hamh va cs. 2015) dd xac dinh giai doan phat trien cua tuyen sinh due ngao ddu.
2.2.2. Phuang phap xac dinh kich thudc thanh thuc sinh due lin ddu
Kich thudc thanh thuc sinh due lan dau dugc xac dinh cho nhdm ca the cd kich thudc nhd nhat ma trong dd 50% sd ca the ed tuyen sinh due b giai doan III, IV qua phuong phap dd thi (Nguydn Chinh, 1996). Mau ngao dugc chia thanh cac nhdm kich thuoc tuong ling nhu sau: 30-39 mm, 40-49 mm, 50- 59 mm, 60-69 mm, 70-79 mm.
2.2.3. Phuong phap xac dinh ca cau gidi tmh trong quan dan
Nhin vao hinh dang ben ngoai va kich thudc khdng xac dinh dugc gidi tinh cua ngao diu. Phan biet gidi tinh due, cai cua ngao dau bang each tidn hanh giai phau de quan sat tuyen sinh due. Xac dinh CO cau gidi tinh theo kich thudc dua tren sd luong ca the due va ca the cai, ca the khdng phan biet quan sat duoc thdng qua mlu ngau nhien b cac kich thudc tai cac lan thu man, phan chia theo nhdm kich thudc.
flieo chidu dai vd mdi nhdm each nhau 10 mm, thu mSu 30-40 ca the/nhdm.
2.2.4. Phuongphap xac dmh mua vu smh san Ddi vdi ngao, vao miia sinh san tuyen sinh due phat trien chen lap eae CCT quan ndi tang khac. Rat khd de cd the lay dupe toan bd tuyen sinh due cua ngao. Do vay da xac dinh miia vu sinh san cua ngao thdng qua su phat trien cua tuyen sinh due con due, eon cai, su bien thien dd beo va ty le thanh thuc theo thdigian.
Do heo eua ngao dugc xac dinh theo cdng thiie cua Quayle va Newkirt (1989):
% Do beo = X 100
Wfm
W W. khdi lugng toan than (ca vd).Whn. khdi luong than mem.
Ty le thanh thuc dugc xac dinh theo cdng thiic 5o ccm than/i t/iuc foioi doan /// iv\
Soconquansii
2.2.5 Phuongphap xac dinh sue sinh san tirong ddi, tiiydtddi
Cd 122 miu ngao ddu cd kich thudc chieu 40 mm vao miia smh san dupe thu dai tir
mSu va nghien cim; stEC sinh san tuyet ddi (SSSTD) la toan bo tning giai doan III, IV aia mdt ca thd. SSSTD dugc tinh cho timg nhdm kich thudc vao mua sinh san. Ba nhdm kich thudc dd xac dinh SSSTD tuong ung ig. 4(^40 mm, 50-59 mm, 60-69 mm.
Cach xac dinh SSSTD (Fa) nhu sau: Xac d' h tning CT giai doan III, IV can khdi lugng than r^' (Wfm), tach tnmg ra khdi phan ndi tang tron v
KHOA HOC CONG N G H £
(mL) nuoc bien loc sach, can lai phan than mdm dupe (Whnl). Dung dich chiia h-ung duoc hiit bd tap chat ICT lung, khuay deu rdi lay mau (1 mL). Dem tning bang buong dem ddng vat phii du (n) qua.
Tinh sd luong tning trong V (mL) dung dich bang cdng thiic sau:
Fa=ny.V
Trong dd: Fa la siic sinh san tuydt ddi, V la the tich chiia tning.
Sd lugng ngao diing de xac dinh SSSTD la 3 nhdm, mdi nhdm 10 eon.
Sue sinh san tuong ddi (Frg) la he qua eua Fa.
Cu the: Siic sinh san tuong ddi la ti sd giira sue sinh san tuyet ddi vdi khdi lugng toan than (Frgl) hoac khdi lugng than mem (Frg2). Cae edng thiie tinh siic sinh san tuong ddi la:
Frgl-- Frg2--
Wfyn Trong do: W^'khdi lugng ngao (cavd).
W6n: khdi luong phan than mem tham khd.
Do vay trude khi tinh Fa can can khdi lugng than m^m cho timg ea the.
3. KET QUA NGHBI CUU VA THAO LUAN
3.1. c a c giai do^in phat tri^n cua tuy^n smh due 3.1.1. Giai doan 0 (giai doan nghi)
Vd hinh thai ngoai, tuyen sinh due ed kich thudc nho, mau nau rat nhat, ehua cd te bao sinh san, tuyen sinh due chi la nhiing soi manh cua cac td chirc md lien ket, cac ehat can thiet cho qua trinh tao tning va tinh tiling. Rat khd de phan biet duoc due cai, cac te bao sinh due bi thoai hda van cd the nhin thay d mdt sd mlu. Hau het cae nang deu ti-dng rdng va mdt sd nang bi thoai hda (Hinh 2 a & b). Cac md hen ket chiia day lipid va glycogen.
3.1.2. Giai doan 1 (giai doan phat tiien) cae nang tiling ehiia day te hao tinh triing va te bao sinh tinh ddi vdi eon due; ddi vdi con cai tiii nang
tning chira day eae tui noan va noan bao. O giai doan phat hien sdm, eac md hen ket bat dau giam dan, khdng cd su hien dien cua cae tu trudng thanh, quan sat te bao sinh due thay rang tiling cd hinh da dien, meo md day dae, khdng ed su hien dien cua cac tu trudng thanh, ehua phan biet rd rang nhan, tinh trimg chi la nhiing cham nhd, khdng chuyen dgng. O giai doan phat trien mudn cd the phan biet duoc due cai dua vao cae nang trimg chiia trimg va tinh triing, cac md hen kdt bat dau giam dan (Hinh 2 c & d). Luc nay cac giao tu due (tinh triing) va cac giao tir cai (noan bao) rat nhieu, da nhan biet dugc mdt sd tinh triing va ti-iing trudng thanh. Cae nang tning trd ndn gon hon cd chira cac te bao sinh tinh, tinh tii va td bao tning. Su gia tang kich thuoc cae nang tning d giai doan nay eiing vdi su giam kich thudc cua md Men keL
3.1.3. Giai doan 2 (giai doan chin mudi) Tuyen sinh due da dupe lap day va nhd ggn vdi tmh tiling trudng thanh (due) va noan (cai). Tinh trimg dugc dinh hudng vd phia long cua nang trong tuyen smh due due (Hinh 2 0. Trong tuyen sinh due cai, cd the nhin thay nhan va tiii mam trong te bao trimg (Hinh 2 e). Kich thudc nang tang cd thd anh hudng lam giam kich thudc cac md Uen ket-
3.1.4. Giai doan 3 (giai doan sinh san) Nhin hinh thai ngoai tuydn sinh due ed dang cang trdn, kich thuoc tang len tdi da b cudi giai doan nay, san pham sinh due cd the chay ra khi an nhe vao phan than mem va ed the hda tan trong nude. Giao tu dugc tiet ra tir cae nang va budc vao giai doan hoat ddng. Sd lupng tinh triing va trung trong nang da giam, lam Id ra vimg trdng (Hinh 2 g
& h). Cac nang bat dau giam kich thudc va eac md lien ket ldng leo bat dau tang kich thudc. Thoai hda va phan giai te bao xay ra b mdt so giao tii chua duCTC biet den.
3.1.5. Giai doan 4 (giai doan thoai hda)
^SJ:^-^
i n r t V "
ir
^-
• ^'-.-..' _..; .
•-
-"•.'•^.f*ff;' f '-^ '-i^.-
^>¥^:'. m-
•J^i.^ ^"O ( b )
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 4/2019 71
KHOA HOC CONG N G H t
* # « . / • . - • : . . .- ^ ' ^ . . - ' ^
^ ^ ^ ^ '••: '---• s; . . . " © ^
" — 4 ;- ^
( f )
>t--f-Zf---
N^^;f»#V (h)
. " c * g S •
(j)
Hinh 2. Lat cat Beu ban cac giai doan phat trien tuy& sinh due ngao ddu (do phdng dji lOx) (a) (b): giai doan 0 (giai doan nghi): (c). (d): Ciai doan I: (e), (f): guu cfoan 11: (g), (h): gia, doan ill: (l), 0: giai doan fV.
(0: Nang trung (tinh): (Av): ming trung (tinh): (do): cic te bio tidng dang phat dien: (ct): mo lien kSt mo: cac te' bao tning dirdng thinh: dgs: cic te bio trung (tinh trung) thoii hda: gv: dii noan: m-nid co- n:
nhan: sz: dnh trimg: sd: tinh tii: s: khoang chua tmh
Day la giai doan sau de, tuyen sinh due gan het Ion cac giao tu dugc sit dung h-ong qua tri h inh cac san pham sinh due, chi con sot lai vai noan biio san, trong khi cac giao tu khong su fl„„ " ^ . giai doan chin, tuyen sinh due nhu co lai, m«m nhun, chong bi thoai hoa. Kich thuoc cua cac nj^g , " ™.
bi chia cat boi cac dang trong sudt dang rS cay. Phan hoa g,am dan, nhung mot sd nang vJi, jj^^ ^^. ,"'
KHOA HOC CONG NGHE dang. Cac md hen ket bat dau dugc lap day bang lipid
va glycogen. Tuy^n sinh due da sin sang cho giai doan nghi ngoi (Hinh 21 &j).
3.2. Mua vu sinh san
3.2.1. Suphat trien tuyen sinh due theo thdigian Tir bang 2 eho th^y su phat trien cua tuyen sinh due ngao dau thay ddi rd rdt theo cae thang nghidn ctru. Ty le ca th^ cd tuydn sinh due giai doan 0 cao nhat d thang 12 dat 42,2%, va giam thap tii thang 1
den thang 8, ti-ong dd thap nhat tii thang 5 den thang 7. Ben canh dd, ca the ngao cd tuyen sinh due giai doan I xuat hien CT tat ea cac thang, ti-ong dd tap hung vao nhiing thang tii thang 10 den thang 2. Cac ca thd ngao ed tiiyen sinh due giai doan III bat dau xuat hien vao eudi thang 3 (19,4%) va chiem da sd trong quan dan tie thang 4 ddn thang 6. Ket qua nay cho thay miia vu sinh san ngao d vimg dam pha Thira Thien - Hue bat dau hi cudi thang 4 va dau thang 5.
Thang 10 11 12 1 2 3 4 5 6 7 8 9
n 40 42 45 36 49 31 51 45 35 45 44 44
B ^ 2 Suph4t ri^nttiy in sinh due ngao diu aua cic thang trong nam Giai doan phat trien tuyen sinh due 0
(con) 6 11 19 13 15 2 2 0 1 1 6 8
Tyle
(%)
15,0 26,2 42,2 36,1 30,6 6,5 3,9 0,0 2,9 2,2 13,6 18,2
1 (con)
20 23 22 23 34 10 5 1 1 1 5 4
Tyle
(%)
50,0 54,8 48,9 63,9 69,4 32,3 9,8 2,2 2,9 2,2 11,4 9,1
11 (con)
7 4 4 0 0 13 6 1 2 4 8 10
Tyle
(%)
17,5 9,5 8,9 0,0 0,0 41,9 11,8 2,2 5,7 8,9 18,2 22,7
III (con)
2 0 0 0 0 6 30 16 11 15 10 13
Tyle
(%)
5,0 0,0 0,0 0,0 0,0 19,4 58,8 35,6 31,4 33,3 22,7 29,5
rv
(con) 5 4 0 0 0 0 8 27 20 24 15 9
Tyle
(%)
12,5 9,5 0,0 0,0 0,0 0,0 15,7 60,0 57,1 53,3 34,1 20,5 Ket qua nghien cuu mua vu smh san eua ngao
dau b nghien cim nay hoan toan phii hpp vdi nghien ciiu cua Jayabal va Kaiyani (1987) khi cho ring miia vu sinh san cua ngao dau keo dai hi thang 2 ddn thang 9 va cung gdn tuong duong vdi miia sinh san b Thai Lan (Nugranad 1999). O An Dd, Mane va Nagahluchanam (1987) eho biet ngao dau sinh san tap trung tii thang 10 - 11 hang nam. O Malaysia, Hamli va cs. (2015) eho biet, loai ngao trang (Meretrix lyrata) co the thanh thuc quanh nam va sinh san tap trung tir thang 7 den thang 9 hang nam.
Ket qua nghien ciiu eho thay ngao thanh thuc sinh due sdm hon so vdi nghien ciiu cua Dd Cdng Thung va Nguydn Dang Ngai (1997), miia smh san cua ngao dau bat dau tir thang 6 den thang 10 duong lich. Ngao thanh thue khdng ddng loat va de phan dpt la do tac ddng eua nhidt do den ngao khdng ddng deu. c a thd CT bai ndng (vimg tneu cao) hap thu duoc nhieu nhiet tir anh ndng mat trdi nen thanh thuc sdm
hon so vdi nhirng ea the sdng d viing sau (vimg trieu thap).
Nhu vay, trong eimg mdt loai, ngao sdng CT cac vimg dia ly khac nhau thi miia sinh san eung khac nhau, phu thudc chii yeu vao su thay doi nhiet do mdi trudng nude. Do vay mdi viing sinh thai khac nhau ddu can cd nhung nghien eiiu tim hidu de nam vimg duoc miia vu sinh san lam can cii chinh xac cho viec lap ke hoach san xuat gidng nhan tao ngao dau trong nam, ddng thdi lap ke hoach bao tdn va phat tnen ngudn lgi khi ngao vao miia sinh san chinh.
3.2.2. Bien thien sdca the thanh thuc Dong thdi vdi xac dinh cac giai doan phat tri^n eua tuyen sinh due ngao qua eac thang trong nam, nhdm nghien ciiu cung hen hanh khao sat ty le ca the thanh thuc theo thdi gian trong nam, ket qua eu the nhu bang 3.
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 4/2019 73
KHOA HOC CONG M S M t
Thang So mlu (con) Sd con thanh thuc
Tyle(%) 10 40 7 17,5
11 42 4 9,5
Bang 3. Bi^n thien sd ca th^ thanh thuc 12
45 0 0,0
1 36 0 0,0
2 49 0 0,0
3 31 6 19,4
4 51 38 74,5
5 45 43 95,5
6 35 31 88,6
7 45 39 _ § ! V L J
8 _ 1 4 _ 2 5 i
56,8 9 44 22 50,0 Qua sd heu bang 3 eho thay cac ea thi ngao dau
thanh thuc xuat hien a vimg ciia bien Tliuan An, dam pha Tam Giang tii thang 3 (19,4%) cho ddn thang 11 (9,5%), ti-ong dd ty le thanh thuc cao nhat vao thang 5 dat 95,5%, sau do bat dau giam dan. Ket qua nghien eiiu nay eao hon nghien eiiu ciia Thangavelu va es.
(2008) cho biet chi ed 60% CT miic dp chin mudi sinh due, con lai 40% cae te bao sinh due CT giai doan nghi va thoai hda.
3.2.3. Bidn thien do beo
Thang 10 11 12 1 2 3 4 5 6 7 8 9
n 40 42 45 36 49 31 51 45 35 45 44 44 Trung binh
Dd beo (%) 15,07 ±1,72 13,86 ±2,63 12,62 ± 1,68 10,44 ±2,04 13,52 ±2,76 15,74 + 2,32 19,61 ± 3,36 19,83 ±2,75 19,25 ±2,67 18,83 ±1,84 18.46 ± 2,06 17,42 ±3,15 16,22 + 3,14
Dd beo la mdt trong nhimg chi sd co lien quan mat thiet den sinh san cua ngao ndi rieng va sinh v|t thuy sinh ndi chung. NhSra tao co SCT viing chac cho viec du doan miia vu sinh san ciia ngao, nhdm nghien ciiu da xac dinh do beo ciia ngao qua cac thang nhu trong bang 4.
Qua sd heu bang 4 cho thay, do beo cua ngao dau CT viing dam pha Tam Giang tang dan tir thang 1 (10,44%) den thang 6 (19,25%) sau dd giam dan. Ngao dau cd do beo cao tir thang 4 (19,61%) den thang 6 (19,25%) va bat dau giam dan tii thang 7 (18,93%) den thang 1 nam sau (10,44%). Theo Nguydn Chinh, vao miia sinh san ddng vat than mem beo hon do tich luy vat chat eho qua trinh sinh san. Nhu vay, can eii vao do beo cua ngao dau budc dau cd the kdt luan r^g miia sinh san eua ngao ddu tai Thira Thidn - Hue bat dau tii thang 4 den thang 8 trong dd tap trung cao nhat vao thang 5,6 va thang 7.
Tir cae sd Ueu ve do beo, ty le thanh thuc, sy phat tiien hiyen sinh due theo thdi gian ed th^ k^t luan rang: Miia de eua ngao CT vimg dam pha Tam Giang bat dau cudi thang 4 den tiiang 8, de rd vao thang 5, thang 6 va thang 7.
3.3. Co c^u gidi tinh
Thang 10 11 12 1 2 3 4 5 6 7 8 9 Ghi chu: Ki
MSu(N) 40 42 45 36 49 31 51 45 35 45 44 44 ''B:Ngaodc
Bang 5. Su bi^n thien ty le dt KPB
17 20 28 19 20 5 6 4 2 3 2 3 u cd tuydn
Tyle
(%)
42,5 47,6 62,2 52,8 40,8 16,1 11,8 8,9 5,7 6,7 4,5 6,8 sinh duckt
Sdcon due
9 7 7 8 13 12 23 21 16 22 20 18 hdngphan
ic cii theo thdi ^an Tyle
(%)
22,5 16,7 15,6 2 2 ^ ^ 26,5 38,7 45,1 46,7 45,7 48,9 45,5 40,9 bietdutyc
Sd con cai 14 15 10 9 16 14 22 20 17 20 22 23 due, cii.
Tyle
(%)
^ 35,0 35,7 22,2 _ _ 2 5 j 0 _
45,2 43,1 44,4 48,6 44,4 50,0 52,3
Tyle
_ 0,9 0,9 _ _ 1 ^
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 THANG
KHOA HOC CONG N G H £
Co ciu gidi tinh la chi so quan trgng trong nghien ciiu sinh san eua ddng vat thuy sinh ndi ehung va ddng vat than mem ndi rieng. Trong pham vi ciia nghidn ciiu, da khao sat su bien ddng CCT eau gidi tinh theo thdi gian va theo nhdm kich thudc.
Bidn ddng CCT cau gidd tinh qua cac thang trong nam dugc th^ hien eu thd dbang 5.
Ngoai trir cac thang ngoai miia sinh san (tir 10 d^n 2), nhimg thang khae trong nam deu bat gap nhirng ea the gom eon due, eon cai va d ea giai doan khdng phan hiet (KPB) due cai. Vao miia sinh san (tir thang 4 den thang 8), ty le ca the khdng phan biet gidi tinh giam dan dang ke, thay vao dd b thdi ky nay ty le due cai cao nhat, cu the sd lugng ea the due cai
B^ng 6. Su bi^n thifen ty 1^ due cai theo nhdm Idch thudc
tap trung vao cac thang sinh san (thang 4-8) va ty Id due/cai vao miia sinh san dao ddng 0,9 - 1,1. Ty Id due cai eiia ngao dau CT dam pha Tam Giang la hoan toan phii hpp vdi ket qua cdng bd eua Jayabal va Kalyani (1986) khi bao cao ty le due cai cua ngao CT eiia sdng Vellar An Do la 1:0,98. Ket qua nay eao hon so vCTi cdng bd cua Nguydn Xuan Thanh (2013), Sawant va Mohite (2013) khi bao cao ty Id duc/cai cua ngao dau b vimg Maharashtra, An Dp la 0,78.
Dong thdi khao sat su bien ddng eiia eo eau gidi tinh tiieo thdi gian, nhdm nghien ciiu eiing da khao sat su bidn ddng eo cau gidi tinh ciia ngao dau theo nhdm kich thudc dugc md ta trong bang 6.
Kich thuoc (mm)
<40 40-50 51-60 61-70
>70
Mau(N) 34 170 102 42 30
Sd con due 15 81 49 20 13
Tyle(%) 44,1 47,6 48,0 47,6 43,3
So con cai 19 89 53 22 17
Tyle(%) 55,9 52,4 52,0 52,4 56,7
Tyle Duc/Cai
0,79 0,91 0,92 0,91 0,76 Ty Id con due ed xu hudng giam dan CT nhirng
nhdm cd kich thudc Idn. Trong khi dd ty le con cai cd ehieu hudng tang CT nhiing nhdm cd kich thudc Idn.
Ket qua nay phii hgp vdi nghien eiiu eua Hamh va cs.
(2015) khi nghien cuu ehu ky sinh san cua loai Meretrix lyrata b Malaysia. Mae dii, eon due trong quan dan thudng ehidm uu the so voi con eai, nhung thudng ty le due cai la can bang (Mohite, 2006).
3.4. Kich thudc thanh thuc sinh due Mn ddu Kich thudc thanh thuc lan dau duoc xac dinh eho nhdm ca the kich thudc nhd nhat cd tuyen sinh due phat trien CT giai doan III, IV chiem ty le 50%
trong sd ca thd eua nhdm. Kich thudc cua nhdm ea the khi chin smh due Idn ddu dugc xac dinh qua dd thi CT diem ma tai dd 50% sd ca the la chin mudi sinh due. Kich tiiudc thanh thue sinh due Idn dau dupe thd hidn qua bdng 7 va hinh 3.
Ket qua cho thay, ngao thanh thuc sinh due lan ddu b kich thudc 40 mm. Ket qua nay cung phii hpp vdi nghien eihi ctfa Nguydn Xuan Thanh (2013)_.khi cho rdng eua ngao dau (M. meretrhd phan bd vimg tneu Nam Dinh ed kich thudc thanh thuc lan ddu dat 40 mm, Idn hon loai ngheu ben tre (M. lyrata) cd kich thudc thanh thuc Idn dau dat 30 mm. Ket qua ngay la CO SCT khoa hoc quan trpng de d6 nghi vide sir
dung ngao bd me cho san xuat gidng nhan tao ngao dau, ndn lua chgn ngao bd me cd chieu dat Idn hon 40 mm va khdng nen khai thac ngao ed chieu dai nhd hon 40 mm, giiip chung ed dieu kien tham gia sinh san bo sung tai tao qudn dan nhdm bao tdn va phat trien ngudn Ipi ngao dau trong tu nhidn.
Bang 7. Kich thudc thdnh Qiuc smh due Idn ddu Nhdm
(mm) 30-39 40-49 50-59 60-69 70-90
Khdi luong (g)
13,2 23,5 53,1 79,7 149,3
Tdng sd
34 170 102 42 30
Con thanh thuc
4 96 84 36 25
%
11,8 56,5 82,4 85,7 83,3
30-.19 JCl-49 ?0-.S9 60-69 "0-"<J N h n m kich thuiVc
Hmh 3. Kich thudc thdnh thue sinh due lan dau
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 4/2019 75
KHOA HOC C d N G NGHE
3.5. Suc^inh san tuong ddi, tuyet ddi Bang 8 cho thay, ngao ddu co kich thudc cang Idn thi sue sinh san cang cao va ngupc lai. Ngao ddu thanh thuc vdi kich thudc chi6u dai tucmg ung 40-69 mm, sue smh siin tuyet doi (Fa) trung bmh dat 1.253.667 himg/ca the, dao dong 330.000-2.820.000 tning/ca the. Sue sinh san tuong ddi tinh theo khdi
luong toan than (Frg 1) dat trung binh 25.231 tning/gam, dao dong 12.791-41.461 trung/gsm. Sue smh san tuong ddi tinh theo khdi luang than mem (Frg 2) dat trung binh 165.268 tning/gani. dao dong 48.571-307.453 ming/gam. So sanh voi sue smh san cua ngao dau, ket qua t e n hoan toan phii hop vcri nghien cuu cua Nguyen Xuan Thanh, 2013.
Nhdm kich thuoc (mm) 40-49 50-59 60-69
Bang 8. Sire sinh san Sue sinh san tuyet ddi
(trung/ca the) 758.000 ±231.699 1.039.000 ±185.799 1.964.000 ±438.487 Trung binh 1.253.667 ± 601.369
s.w- sinh <;ai, tirnnff ddi (tning/g) F r g l
24.845 •<- 6.591 21.170 + 3.443 29.678 ± 6.970 25.231 ± 6693
Frg 2 180.601 ± 92.813 191.423*27.273 191.423 ±42.758 165.268 ±66.197 4 . KET LUAN VA BE NGHI
4.1. K ^ luan
Qua trinh phat trien tuyen sinh due cua ngao ddu CT ddm pha Tam Giang trai qua 5 giai doan gom: nghi, phat trien, chin mudi, sinh san va thoai hda.
Miia vu sinh san ciia ngao CT vimg ddm pha Tam Giang bdt ddu cudi thang 4 den thang 8, de rd vao thang 5, 6 va 7. Kich thudc thanh thue sinh due lan ddu a i a ngao ddu vimg dam pha Tam Giang CT kich thudc 40 mm; ty le duc/cai vao miia sinh san dao ddng 0,91 -1,05.
Dp beo cua ngao ddu dat 10,44 -19,83%; do beo cua ngao tang ddn tii thang 2 den tiiang 6; giam ddn tir thang 7 den thang 1 nam sau.
Ngao ddu thanh thuc vdi kich thudc chieu dai tuong ling 40-69 mm; sire sinh san tuyet ddi (Fa) trung binh dat 1.253.667 tning/ca the; siie sinh san tuong doi tinh theo khdi lugng toan than (Frg 1) dat trung binh 25.231 Qiing/gam; siic sinh san tuong ddi tmh theo khdi lugng tiian mdm (Frg 2) dat tiimg binh 165.268 tning/gam.
4.2. D^ nghi
Tiep tijc nghien ciiu bo sung cae thang cdn thieu ve dac diem smh hgc ngao ddu de ed CCT sd khuyen cao miia vu sinh san ciia ngao phii hgp vdi didu kien Thira Thien Hue.
TAJ UBJ THAM KHAO
1. Braley, R (1988). Reproductive Condition and Season of the Giant Clam Tridacna gigas and T, derasa utihsmg a Gonad Biopsy Technique. Giant
Clam in Asia and the paeihc, Austi-aiian Centi-e For International Agricultural Reasearch.
2. Dd Cdng Thung va Nguydn Dang Ngai (1997).
Birdc ddu tim hieu dae diem sinh hgc va mdt sd bien phap ky thuat nudi ngao M. meretrix b vimg bi^n Tidn Hai - Thai Binh. Phan vidn Hai duong hoc Hai Phdng 27.
3. Hamh, H., M. H. Idns, A. Rajaee and A H.
Kama! (2015). Reproductive Cycle of Hard Clam, Meretrix lyrata Sowerby, 1851 (Bivaivia: Veneridae) h-om Sarawak, Malaysia.
4. Jayabal, R. and M. Kalyani (1986). Age and growth of the estuarin elam (Meretnx meretrix) inhabiting Vellar estijary. Mahasaga - Bulletin of the National institute Oceanography V^, (2): 141 - 145.
5. Jayabal, R. and M. Kalyani (1987). Seasonal variations in biochemical constituents of different body components of Meretrix meretrix (L).
6. Liu, B. Z., B. Dong and B. J. Tang (2006).
Effect of stocking density on growth, settlement and survival of clam larvae, Meretiix meretrix Aguacultin-e 25S: 344-349.
7. Mane, U. H. and R. Nagahluchanam (1987).
Reproductive m edible bivalve shellfishes of Ratnagmi coast National seminar shellhshes resources and fanning. 167-178.
8. Mohite, S. A. (2006). Biology, ecology and culture of Paphia malabarica. Ph. D. thesis D Balasaheb Sawant Konkan Krishi Vidyane th (Agricultiiral University). Dapoh, hidia.
9. Nguydn Chinh (1996). Mdt sdloai ddng vat than mem (MoUusca) cd gia tri kmh te d biSn v v Nam. NXB Khoa hgc Ky thuat Ha Ndi. '
KHOA HOC CONG NGHE
10. Nguyen Thi Xuan Thu (2005). Tdng quan ve 13. Quayle, D. B. and G. F. Newkirt (1989).
tinh hinh nghita cilu san xuat gidng va nudi dong vat Farming Bivalve Molluscs: Methods for Study and than mem d Viet Nam - Dmh hudng phat trien. Hdi Development The World Aquaculture Society.
thao toan qude ve nghien cilu va ling dung khoa hpc ^^ gawant, P. P. and S. Mohite (2013).
" ° i " £ t ? l ° " ' ^ ™ . ™ ' ' ™ ' ^ * r ' ' " ' ' ^ ^ " ° ™ Reproducdve development in estiiarine clam, Mmh. NXB Ndng nghiep, TP, Hd Chi Minh. ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ „ „ ^ ^le south west coast of
11. Nguyfa Xuan Thanh (2013). Dac diem sinh Maharashtra, India.
hoc sinh san cua ngao ddu (Meretrix meretrix) tai 15. Tang, B., B. Liu, Q. Wang, T Zhang and J.
vimg Wen ven bien tinh Nam Dinh. Tap ehi Khoa x,ang (2006). Effects of various algal diets and hoc va Cdng nghe Bien 13, (4): 357-364. starvation on larval growth and survival of Meretrix
12. Nugranad, J. (1999). Breeding of the oriental mereWx.^(7i/ac«//ure 245: 526-533.
hard Clam (M./-e&K/nereM^.Proceedmgs of the ig Thangavelu, R., P. Poovannan and N.
10th Congress and Workshop Tropical Marine Rudramurthy (2008). Distribution of Bivalve Mollusc Programe, Phuket Marine Biological Center resources in Kandeleru Estuary, Krishnapatnam Special pubUcation. .g^^^^^ Nellore Distnct, Andhra Pradesh. Mar. Fish.
Info. Ser TandESerWS: 8-12.
STUDY ON REPRODUCTIVE BIOLOGY OF ASIATIC HARD CLAM Meretrix meretrix (Linnaeus, 1758) OFTHUAN AN INLET, THUA THIEN - HUE PROVINCE
Nguyen Van Huy, Tran Vinh Phuong, Phan Thi Thu Hong Summary
The present study was conducted to determine the reproductive biology of Asiatic Hard Clam (Meretrix meretrix Linnaeus, 1758) for seed producUon and grow-out. A 30-50 clam samples were collected monthly at surounding Thuan An inlet, belong to the Tam Giang lagoon Tliua Thien - Hue province. The results showed that the gonad development of the clam was devlded into five stages: rest stage; developmental stage; mature stage; spawning stage; and spent stage. The spawning season of the clam started irom april to august. Peak spawnmg was between may and June. The size at which Meretrix meretrix reached its iiret maturity was 40 mm in length; Annual sex ratio male: female ranged irom 0.9 to 1.1. The condition factor (index) of Meretrix meretrix ranged from 10.4 tol9.8%; increasing from februaiy to June and decreasmg irom July to januaiy. The absolute and relative fecundity of Meretnx meretnx at the size from 40-69 mm was 1.253.667 eggs/individual and 165.268 eggs/g, repectively.
Keywords: Meretrix meretrix, reproducnve biology, Tam Giang lagoon.
Ngudi phan bita: PGS.TS. H6 Thanh Ha Ngiy nhan b4i: 7/12/2018
Ngay thdng qua phan bita: 8/01/2019 Ng4y duyet dang: 15/01/2019
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 4/2019 77
