HQI NGHI KHOA HQC T O A N Q U O C V £ SINH THAI V A TAI N G U Y £ N SINH VAT LAN THLf BA
MQT SO DAC DIEM SINH H O C CUA LOAI CA NIEN QUANG NGAI ONYCHOSTOMA GERLACHI(Peters, 1880)
TRAN VAN TRQNG Trung tam Nhiet doi Viet- Nga Ca Nien (hay cdn gpi la ca Sinh)-Onychostoma gerlachi (Peters, 1880) la loai ca kinh te cua nude ta. Tai Quang Ngai va khu vyc mien Trung, loai ca nay cd gia tri nhu mgt loai hai dac san. Trong nhting nam gin day lugng ca Nien tai Quang Ngai bi khai thac mgt each qua miirc bang nhieu hinh thurc khac nhau. Chinh vi vay ma nguon Igi ty nhien tai day giam di mgt each dang ke. Tai lieu d nude ngoai va trong nude dl cap den ca Nien cdn rit ban che, mdi d khau md ta, phan loai.
D I gdp phin bao tdn quy gen va phyc hoi ngudn Igi ty nhien, viec nam vung cac dac diem sinh hgc cua chiing la mgt yeu ciu cip thilt. Trong bai viet nay, trinh bay nhting ket qua dieu tra, nghien curu mgt sd dac diem sinh hgc cua loai ca Nien Quang Ngai nam trong khudn khd cua d l tai: "Dilu tra danh gia ngudn Igi, nghien cuu thyc nghiem sinh san nhan tao va xay dyng md hinh nudi ca Nien Onychostoma gerlachi (Peters, 1880) tai Quang Ngai". Ca quan chu quan dl tai la Sd Khoa hgc va Cdng nghp Quang Ngai.
I. DOI T U Q N G V A P H U O N G P H A P NGHIEN ClTU 1. Thdi gian va dja diem nghien cihi
Thdi gian nghien curu tir thang 11 nam 2004 din thang 5 nam 2007. Dilu tra thu mau dugc thyc hipn tai 8 diem d thugng ngudn ba con sdng Idn d Quang Ngai la sdng Tra Khiic, sdng Tra Bdng va sdng Ve; nam tren dia ban cac huypn mien mii nhu Ba To gom 2 diem (thi tran Ba Ta va thj hi Ba Vi); San Ha 3 dilm (Son Ba; San Ha, San Thanh); San Tay 1 dilm (thj tran San Tay) va Tra Bdng 2 diem (Tra Xuan, Tra Thg).
2. Phuong phap nghien cuu
Tien hanh phan tich tren 300 mau ca cd kich thudc khac nhau, thu dugc tai cac diem nghien curu va thdi gian khac nhau. Cac phuang phap nghien curu thudng dugc su dyng trong nghe ca nhu: Ngu loai: theo Pravdin, 1973; Mai Dinh Yen, 1978, Nguyen Van Hao, 1993; Sinh truang:
theo Pravdin, 1973, Bagenal, 1978; Sinh san: theo Nikolski,1961; Pravdin, 1973; t l bao hgc theo David E. Hinton, 1990; Dinh duang theo Bagenal, 1978; Bouski,1972; Dieu tra sinh thdi moi truang, san luang vd phan bo: tryc tiep thu mau, theo ddi cac me danh ca va phdng van tryc tiep ngu dan, thu thap sd lipu qua cac chu thu gom mua ban ca. Nghien cuu cac dieu kien mdi trudng thuy ly, thiiy hda va thuy sinh theo giao trinh cua Trudng Dai hpc Nha Trang. Xir ly sd lieu bang phan mem Excel.
IL KET QUA NGHIEN ClTU 1. Dac diem hinh thai phan loai
Vj tri phan loai cua ca Nien Quang Ngai tucmg ty nhu vi tri phan loai ca Sinh cua cac tac gia Mai Dinh Yen (1987), Bd Thiiy san (cu) (1996) va Nguyin Van Hao (2001) da cdng bo, cy thi nhu sau: Nganh dgng vat cd xucmg sdng: Vertabrata
Ldp ca xuang : Oteiformes Bg ca Chep Cypriniformes
HQI NGHI KHOA HOC TO^N QUOC V£ SINH THAI VA TAI NGUY£N SINH VAT LAN THl> BA Hg ca Chep Cyprinidae
Hg phu ca Trdi Barbini
Gidng ca Sinh Onychostoma
Loai ca Sinh Onychostoma gerlachi (Peters, 1880)
Ten ggi: Quang Ngai ggi la ca Nien; Quang Nam gpi la ca Mac, ca Nien.
2. Dac diem hinh thai cau tao
Mau ca thu dugc cd chieu dai tir 8,1cm din 37,5cm va khoi lugng tir 6,5g din 450,0g. Phan tich ve hinh thai cau tao cho kit qua nhu sau: D = 4,8; A = 3,5; P = 1,14; V = 2,8.
Sd lugng vay dudng ben: Sq = 47 7 - 8 4 - 5 48.
Ve mau sac: Lung ca cd mau xam, bung mau tring bac. Khi ca bai nghieng minh dudi nude tim moi trong cac khe da rat de phat hien vi chiing lip lanh mau anh bac (hinh 1).
_ Ve khdi lugng: Theo ngu dan tai dia phuang cho biet ca cd khoi lugng to nhat ma hg da timg bit dugc la 2kg (khdng thu dugc mau).
Bdng 1
STT 1 2 3- 4 6 7 8 9 10 11
Mgt so chi tieu chii yeu ve hinh thai cau Chi tieu hinh thai
Chieu dai than L (cm) Chieu dai bo vay dudi L„ (cm) Khdi lugng than P (g) Chieu dai mom Ot (cm) Chieu dai dau T (cm) Chieu cao than H (cm) Chieu dai nipt (cm) Chieu dai rudt/Lo Tyl?:H/L„(%) Ty le: T/Lo (%)
TB 18,70 ±7,11 14,90 ±5,41 87,32±5,40
1,31± 0,40 2,75 ±0,82 5,02 ± 1,54 122,10±31,61
6,04± 0,77 29,20± 2,00 20,20 ± 3,23
tao Min 8,12 6,70 5,00 0,62 1,65 2,53 60,00
4,10 26,00 12,53
Max 37,51 27,00 400,00
2,52 5,00 8,53 180,00
7,00 37,51 27,11
Hinh 1: Hinh dang ben ngoki c4 Nien- Onychostoma gerlachi (Peters, 1880)
Tnprg luong (g) 450
y = 0.026ax""
R' = 0.9451
Hinh 2: Do thj bieu dien sy tu-omg quan giira chieu dai vi lihoi Iiryng
HOI NGHj KHOA HQC TOAN Q U 6 C Vg SINH THAI V A TAI N G U Y £ N SINH VAT LAN THLf BA
3. D5c diem ve sinh trudng va dinh dudng
3.1. TuoTig quan giira chieu dai \k khoi lugng: Dya vao so lieu phan tich cac mlu ca, chiing tdi xac dinh dugc phuang trinh tucmg quan giira chilu dai (L) va khdi lugng (P) ciia cA Nien Quang Ngai cd dang nhu sau:
Bdng 2 TuoTig quan giira tuoi, chieu dai va khoi lugng ciia ca Nien Quang Ngai
Chi tieu L(cm) P(g)
1 tuoi 17,5 54,6
2*tuoi 26,2 130,7
3*tu6i 31,6 235,7
4*tu6i 36,7 324,3
Qua hinh 2 va bang 2 thay sy tang trudng cua ca thdi ky dau tang nhanh vl chieu dai, khoi lugng tang khdng dang kl. Ca tang nhanh vl khoi lugng khi dat kich thudc tren 20cm, tren 2*tudi. Ca cang Idn tudl tang khoi lugng cang nhanh.
3.2. Dac diem ve dinh dudng: Ca Nien Quang Ngai bit moi nai ddng nude chay, chiing an thien vl thyc vat, rit it dpng vat. Chinh vi an thyc vat, nen rugt ciia chiing rat dai. Rugt thudng dai gip tir 5-6 lin chilu dai than. Chiing thudng ria cac loai rong tao bam tren da va hay xoay minh khi bit mdi trong cac ke da. Vao nhiJng ngay trdi nang, khi nude cd do trong Idn rat de nhin thiy ca Nien bit mdi. Chiing thudng di timg dan, liet minh lap lanh dudi mat nude.
Bdng 3 Thanh phan thuc an trong rupt ca Nien
Loai thirc Sn Tao khue (Baccillariophyta) Tao luc (Chlorophyta) Dpng vat day (Zoobenthot)
Mirc dp gap +++
+ +
Tan so gap (%) 100
30 30
Bdng 4 Th^nh phan loai tao gap trong ong tieu hda ciia ca Nien Quang Ngai
TT
1 2 3 4 5 6 7 8
Ten tao
Tao Khue : Bacillariophyta Cymbella ventricosa Kutz C tumida (Breb) V . H Gyrp/ionemaaaiminatunFAh G. elegans Grun Na^kuhcrypix^iakKitz.
N. placenta Erhb N. schoenfeldii Rust N. gibba gibba CI
Mirc dp gap
++
++
+
-H- 1 1 1 1 M I I
+++
++
TT 9 10 11 12 13 14 15
Ten tao
Nitzchia regulr Must A'; capitella Hust N. acicularis P.Smith Tao luc Cholorophyta Scen0desmusacuTmalus(]jog)Ox)d£i
S. quadriicauda (Turp) Breb Heterodendron sp.
Sprirogyra sp.
Mirc dp g3p ++-I- +-I- +++
-H-
+-f + ' +
Chii thich: +-H- + nhieu, +++ trung binh, ++ it, + rat it 4. Phan bo va mdi trudng song ciia ca Nien
Ca Nien Quang Ngai phan bo deu khap tai thugng nguon cdc con sdng Idn d Quang Ngai nhu sdng Ve, sdng Tra Khiic va sdng Tra Bdng. Ranh gidi cudi ciing ma chiing phan bd ve phia ha luu ddi vdi sdng V? la tai Long My (xa Binh Minh, huypn Binh Son); doi vdi sdng Tra Khiic la tai Son Thanh (huypn Son Ha); ddi vdi Sdng Vp la tai thj tran Ba Ta (huypn Ba Ta). Ca chu yeu tap trung sinh song tai cac ddng thac cd nude chay thudng xuyen vdi dg sau va tdc dg nude
HQI NGHI KHOA HQC T O A N Q U O C V £ SINH THAI VA TAI NGUY£N SINH VAT LAN THLT BA
chay khac nhau. Ddi vdi ca cd kich thudc be tir 8-12cm, thudng tap trung nai cd mirc nude can 0,5-1,Om, van toe nude 0,5-0,6m/giay. Ddi vdi ca Idn cd kich thudc tren 12cm, thudng tap trung nai cd do sau tren Im, van tdc nude 0,3 - 0,5m/giay hoac nai cd ddng nude quan xoay. Dieu kipn mdi trudng thich hgp cho ca sinh sdng va phat trien la: nhipt dp nude 22-27 C, pH 7,5; dxy hda tan 7-lOmg/lit; dp trong 0,6-1,0m; nIn day la da cd nhilu rong reu bam.
5. Hinh thirc, miia vu va san lugng khai thac
Ca Nien d Quang Ngai dugc khai thac tai cac ddng sdng, sudi cd dp sau tir_0,5-4,0m. Ngu cu khai thac la ludi re, quang chai, cham dien va danh min. Ca dugc khai thac gan nhu quanh nam nhung tap trung chii ylu vao cac thing miia khd (tir thang 1 din thang 9 duang lich). Cac thang miia mua, cd nude lu, san lugng khai thac khdng dang kl. Ca dugc tieu thu ngay tai cac chg dja phucmg va trong cac nha hang. Ca Idn nhit ma ngu dan da tirrig danh bat dugc la 2kg. Cdn ket qua dilu tra cho thiy ca cd kich thudc Idn nhit la 37,5cm, khdi lugng 450g va ca the nhd nhit cd kich thudc 8,1cm va khoi lugng 6,5g.
6. Dac diem ve sinh san
6.1 Phan bi|t ca dye, ca cai: Khi ca cdn nhd, sy phan bipt vl hinh thai ben ngoai giti-a ca dye va ca cai rit khd. Khi ca da thanh thyc, vao
miia sinh san cd sy khac bipt vl hinh thai gitira ca dye va ca cai. Ca dye thudng cd than hinh thon dai ban ca cai. Bung ca cai phinh to. Lo nieu ca cai cd mau hdng. Lo nipu ca dye cd mau trang nhat. Dac bipt din miia sinh san thi cacai cd hipn tugng lung gii cao len rat de nhan bilt ban ca dye. Ca cai thudng cd khoi lugng va tudi Idn ban (hinh 3)
Hinh 3: Mat byng ca cai va ca dye 6.2. Miia sinh san, tap tinh sinh san: Ca Nien Quang Ngai ngoai ty nhien sinh san moi nam mgt lin. Thdi gian sinh san tir thing 11 nam trudc din thing 4 nim sau, nhung tap trung nhit la tu thing 2 din thing 4 duang lich. Trong thdi gian niy tren 80% sd c i the cd tuyen sinh due d giai doan IV-V. Vao miia sinh sin, khi trdi mua phim, nhiet dp xuong thap tu 22,5 C- 24 5"C thi ci bit diu de. Thdi gian de tir nira dem trd ve sing. Ci di de theo dan. Khong bat cap timg ddi mgt. Tir nai sdng cd dp sau Idn, c i bit diu di cu ra viing cd dp sau thap de de. Nai de la cac ddng thic can, cd nIn diy di, dp sau tir 0,3-0,5m, nude chiy nhp cd van toe 0,5- 0 6m/giay, dp trong cao tren Im. Diu tien, ci dye bai ngugc ddng nude ep bung xuong day da va tudi tinh ra, sau dd c i cai theo sau de trung. Trimg de ra rai xudng day, dinh vao nen day da.
Tir dd nd ra c i con. C i bd mp sau khi de xong quay ve nai sdng cu. Sd dT ci chpn nai de trung cic dac dilm nhu vay cd thi trinh dugc dich hai, ting cudng kha nang thu tinh cho trung.
6.3. Hp s6 thanh thyc, sue sinh san: H? s6 thanh thyc d giai doan IV-Vcua ci cai^li: 13,23
± 2,15%, c L c i dye la 4,25 ± 0,01. Sue sinh san tuypt ddi la: 7.363 ± 2.752 t r ^ f ^ . ^ ^ e cai sue sinl^ san tuang ddi la: 26±2 trimg/g c i cii. Tudi thanh thyc nho nhat cua ' j ^ ^ f / f ^ tuo, c u a ^ due la rtudi. Kich thudc ca cai tham gia sinh sin trung binh 2.6,2cm va kho'l^dng trung bmh
130,7g. Ddi vdi ca dye, kich thudc trung bmh 19,3cm va khdi lugng trung bmh 55,5g.
'd 4 C^u true tu6i va ty I? dye cai: Qua phan tich cac mlu thu dugc cho thiy ca NiSna Quang Ngai cd ciu t l thanh 4 nhdm tul^ s6 lugng ca thi trong cac nhdm tudi khdng giong nhau (hmh 4 ).
HOI NGHI KHOA HOC T O A N Q U O C V £ SINH THAI V A TAI N G U Y £ N SINH VAT LAN THLf BA
• a due
• a cii
TU{5L 1 + 2+ 3+ 4+ Tu6i
Hinh 4: Bilu do ve thinh phan cac nhom tuoi trong quan dan c4 Nien
Hinh 5: Bieu do ty 1? giira ca dye v^ ca cai theo cac nhom tuoi
Nhdm ca tir 0^ tudi den T tudi chilm ty Ip cao nhit trong dan ca khai thic: 72,5%. Nhdm ci 2* tudi chilm ty le cao thu nhi: 18,3%. Nhdm c i 3'' tudi chiem ty Ip thu ba: 5,5%.. Nhdm c i 4*
tudi chilm ty le thip nhit: 3,7%. Nhu vay, ca cd tudi cao nhit la 4* tudi, khong bit gap ci cd tudi cao han. C i cd nhdm tudi cang cao chiem ty le cang thap. Dieu dd cd the do muc dp khai thic dinh bit qui Idn, nen nhung c i thi Idn ngay cang it di. Cd ci khai thac danh bit chii yeu hien nay nim trong dp tudi tir 0* tudi den 2* tudi.
Kit qua khao sit vl ty Ip giira ca dye va ca cai trong quan dan cho thay cd sy khic nhau trong cac nhdm tudi (hinh 5).- Nhdm ca 1* tudi: Con dye chilm 60,3%, khdng xac dinh dugc gidi tinh 39,7%;
Nhdm ca 2* tudi: Con dye chilm 55,1%, con cii chilm 44,3%; Nhdm c i 3* tudi: Con dye chiem 31,4%), con cai chilm 68,6%).; Nhdm c i 4* tudi: Con dye chilm 24,1%), con cii chiem 15,9%.
6.5. D3c diem to chuc hpc tuyen sinh dye ca Nien Quang Ngai: Cac giai doan phat hien ciia budng trung (noan sao) va tl bao trung (noan bao) cua ca Nien Quang Ngai cung giong nhu mgt so loai trong hg ci Chep (buong triing chia thanh 6 giai doan va te bao trumg chia thanh 5 thdi ky).
Bdng 5 Tom tat thdi gian phat trien phdi ciia ca Nien Quang Ngai (Onychostoma gerlachi)
Nhipt dp nude: 24,5-25,5^; pH: 7,6-7,8; oxy hda tan: 7,4-8,5mg/lit TT
1 2 3 4 5 6 7 8 9 10 11
Cac giai doan phat trien Trimg sau khi thu tinh
Giai doan phan cat 2 te bao Giai doan phan cit 4 te bao Giai doan phan cit 8 te bao Giai doan phan cat nhieu te bao Giai doan phdi nang
Giai doan phdi vi Giai doan phdi than kinh Giai doan bpc mit, mam dudi Hinh thanh hp mach mau, tim dap nhp Ca nd, 6m noan hoang
Thdi gian sau thy tinh (Gid:Phut) 00:00
00:30 01:45 03:37 06:25 10:19 16:45 25:40 33:10 42:50 48:10
HOI NGHI KHOA HOC T O A N Q U O C V& SINH THAI VA TAI NGUYEN SINH VAT LAN THLf BA
thoi ky V , Giai doan V Hinh 6: Buong triing
giai doan V Then ky IV,
Gidi doan IV
r r ii
't
Hmh 7: Tinh s^o giai doan V
^'
Hinh PTriing 10 x 40
1 Ciid] d<.kin III »
Hinh 8: Buong trirng 10 x 40
Hinh 10: Tinh sio 10 x 40
Hinh 11: Giai doan phoi vj (10 x 40)
Hinh 12: Giai doan hinh th^nh bpc rait, mam duoi (10x40)
HOI NGHj KHOA HOC TOAN Q U O C Vfe SINH THAI VA TAI NGUYEN SINH VAT LAN THLf BA
6.6. Cac giai doan phat trien phdi: Khi vira de ra, tning cd nhieu dich nhay lam cho trimg cd tinh dinh. Sau khi de 5-10 phiit, neu bi lay lac manh thi trung se rdi nhau ra va mat tinh dinh.
Trung ca Nien thugc dang bim day. Sau khi thy tinh, phdi bit diu phat trien. Phat triln lien tyc qua nhieu giai doan de cudi cimg cho ra ca the hoan chinh.
Ca Nien Quang Ngai sinh san vao miia xuan, sinh sdng d cic sdng suoi mien niii, vao miia sinh sin nhipt dg nude thudng xudng thap. Cd the day la mgt die diem thich nghi ve sinh sin cua chiing.
m . KET LUAN VA KIEN NGHJ
- Phuang trinh tuang quan giira chilu dai va khdi lugng cua ci Nien dugc xac dinh cd dang:
P = 0 . 0 2 8 8 . L " ' "
- Mdi trudng sdng thich hgp cua c i Nien la nai cd ddng thac chiy thudng xuyen, cd nhiet dp nude tir 22-26°C, pH 7,5, dxy hda tan 7-lOmg/l, chat day la nen da, cat. Thurc an cua chiing la cac loai rong tao bim tren nen diy di.
- Tudi thanh thuc lin dau ciia ca cii khi 2* tudi. Ca dye thanh thuc sdm ban khi 1* tudi. Kich thudc va khdi lugng trung binh nhd nhat khi tham gia sinh san cua ca cai la 26,2cm, tuang ung vdi khdi lugng la 130,7g. Doi vdi ca dye, thanh thuc nhd nhat trung binh la 19,3cm, tuang ung vdi 55,5g.
- Quan dan ci Nien Quang Ngai khai thac ty nhien tai dau ngudn cac con sdng cd cau tnic thanh 4 nhdm tudi. Nhieu nhat tir 0* tudi den T tudi, chiem 90,8%). Nhdm tudi tir 3* tudi den 4*
chiem ty Ip rit thip: 9,2%o. Nhu vay, ca tudi cang cao chiem ty Ip cang thap.Ty le dye cii gitra cac nhdm tudi ciing khdng giong nhau: Ca 1* tudi, con dye chiem 60,3%o, khdng xic dinh dugc gidi tinh 39,7%. Ci 2* tudi, con dye chiem 55,7%o, con cii chiem 44,3%). Ca 3* tudi, con dye chilm 31,4%), con cii chilm 68,6%. Ca 4* tudi, con dye chilm 24,1%, con cai chilm 75,9%. d dg tudi nhd, ty Ip ca dye Idn ban ca cii, cang Idn, tudi ty Ip c i dye cang giim.
- Ci Nien Quang Ngai sinh san mgt Ian trong nim. Miia sinh sin tir thing 11 den thing 4 ducmg lich bing nim. Tap trung chii ylu tir thing 2 den thing 4. He so thanh thuc d giai doan IV-V cua ci cii la: 13,23 ± 2,15%; ciia c i dye la 4,25 ± 0,01. Sure sinh san tuypt doi la:7.363 ± 2.752 trumg/ci the cai; sure sinh san tucmg ddi la: 26±2 trung/g ci cai. Ca Nien Quang Ngai sinh san trong dieu kipn mdi trudng thich hgp la: Nhipt dp nude 22,5-23,5°C, pH 7,6-7,8, dxy hda tan: 7,4-8,5mg/lit'. Trung ci Nien thugc loai trimg dinh khdng hoan toan va chim day.. Kich thudc khi truang nude la 1,5-1,8mm. Thdi gian phit trien phdi tren 48 gid.
Kien nghj
- Nen khai thac ca ca dudi 130g. Vi ca tren 130g thudng la c i da thanh thuc tham gia sinh sin lin dau. Vao miia sinh sin, ban che viec khai thic dinh bat ca bo me tai cac bai de
- Can thanh lap khu vyc bao ton ngudn Igi ci Nien tai khu vyc tir sdng Re thugc thi tu Ba Vi, huyen Ba Ta chay qua huypn San Ha de ci cd dieu kien sinh san va tang ngudn Igi ty nhien.
- Tiep tuc nghien curu de cho ra quy trinh san xuit gidng loai ci Nien Quang Ngai, cd nhu vay mdi chu dgng con gidng cho vipc nudi thuang pham va bd sung nguon Igi ty nhien.
- Tien hanh nghien cuu nudi thuang pham ddi tugng nay trong ao nude chiy d cac khu vyc mien nui.
HOI NGH! KHOA HQC TOAN Q U O C V £ SINH THAI VA TAI NGUY£N SINH VAT LAN THLf BA
TAI L l f U THAM KHAO
1. Nguyen Tudng Anh, 2004: Ky thuat san xuat gidng mpt sd loai ci nudi. NXB. Ndng nghipp, Ha Npi.
2. Bagenal T.B., 1978: Method for assesement of fish production in fresh water. Oxford.
3. Chung Lan, 1969: Dac diem sinh hgc va sinh sin nhan tao cic loai ca nudi. NXB. Khoa hgc va Ky thuat. Ha Ngi.
4. Chu Xinluo, Chen Yinrui, 1989, 1990: Thefish of Yunnan, China.
5. Laurence W. et al., 1990: Reproduction Methods for fish Biology, American Fisheries Society.
6. Naca Technical Manual 7, 1989: Integrated fish farming in China, Bangkok, Thailand.
7. Nikolski G.V., 1961: Sinh thai hgc ca. NXB. Dai hpc va Trung hpc chuyen nghipp.
8. Pravdin I.F. 1963: Hudng dan nghien curu ci. NXB. Khoa hpc va Ky thuat. Ha Npi.
9. Rainboth W.J., 1969: Fish of the Cambodian Mekong- FAO.
lO.Xakun C , N. A Baskaia, 1968: Xic dinh cic giai doan phat due va nghien cim chu ky sinh due ciia ca. NXB. Ndng nghipp. Ha Ngi.
1 I.Mai Dinh Yen, 1978: Djnh loai ci nude nggt cic tinh phia Bic Viet Nam. NXB. Khoa hgc va Ky thuat, Ha Npi.
B I O L O G I C A L C H A R A C T E R I S T I C S O F T H E FISH
ONYCHOSTOMA GERLACHI {PETERS, 1880) IN QUANG NGAI PROVINCE TRAN VAN TRONG SUMMARY
Fishes was colleted on head-water of various rivers of Quang Ngai, from November in 2004 to May in 2007, including Ve, Tra Khue and Tra Bong river.
Every month fish samples were colleted to analysis of physiognomy, size, weight, habitat, length of bowels, ingredient of feed, age groups, male and female rate, reproductive characteristic, process of gonad development, time of embryo development.
The research results show that this species lives at flowing waters from up streams, high transparency, high disollved oxygen, hard bottom is stone. The mam food of fish is many species of mosses attached on bottom stones.
Coefficient of gonad development in stage IV-V of the female: 13.23 ±2.15% and the male:
4 25 ± 0 01%. The female absolute reproduction: 7.363 ± 2.752 eggs/female, the female relative reproduction: 26±2 eggs/g. The age of the first spawning female is 2 years ° d ; the average siz offish is 26.2cm length and 130.7g weight. The age of the fist spawnmg male is 1 year old, the average size offish is 19.3cm length and 55.5g weight.
