Đặc điểm sinh học và nuôi dưỡng cá tỳ bà bướm (sewellia spp ) phân bố tại thừa thiên huế tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING CAN THO UNIVERSITY THE SUMMARY OF PHD THESIS Major: Aquaculture Major’s code: 62 62 03 01 VO DIEU BIOLOGICAL CHARACTERISTICS AND REARING LOACHES (Sewellia spp.) DISTRIBUTED IN THUA THIEN HUE Can Tho, 2020 THE THESIS HAS BEEN ACCOMPLISHED AT CAN THO UNIVERSITY Supervisor: Dr Tran Van Viet Assoc.Prof Tran Dac Dinh The thesis has been approved by the university’s committee Venue: ………………………………………………………………… Time:………date… month… year…… Fisrt reviewer: Second reviewer: Can refer the thesis at: The learning center, Can Tho university National library of Vietnam THE LIST OF PUBLICATIONS Vo Dieu, Tran Van Viet, Phan Do Da Thao, Vo Van Chi, 2019 Feeding habits of tiger hillstream loach (Sewellia lineolata) distributed in Thua Thien Hue province Science and Technology Journal of Agriculture and Rural Development Vo Dieu, Tran Van Viet, Phan Do Da Thao, Vo Van Chi, 2019 Population fluctuation of tiger hillstream loach Sewellia lineolata and spotted butterfly loach Sewellia albisuera distributed in Thua Thien Hue province Science and Technology Journal of Agriculture and Rural Development Vo Dieu, Tran Van Viet, Phan Do Da Thao, 2019 Reproductive biology of tiger hillstream loach (Sewellia lineolata) distributed in Thua Thien Hue province Hue University Journal of Science, 128(3A), 2019 Vo Dieu, Tran Van Viet, Phan Do Da Thao, 2019 Species composition of hillstream loach (Sewellia spp.) distributed in Thua Thien Hue province based on morphological characteristics and DNA barcode Hue University Journal of Science, 128(3C), 2019 CHAPTER INTRODUCTION 1.1 Introduction Vietnam is one of nations having advantages as favorable climate, abundant aquatic organism resource to develop the aquarium industry Lots of ornamental fish species are distributed in Vietnam such as Ctenops pumilus, Rasbora spp., Betta splendens, puffer Of which, species belonging to the genus Sewellia have been considered and collected to supply the domestic and foreign aquarium industry (Vu Cam Luong, 2008) Loaches are distributed with large number in central and highland region as Binh Dinh, Quang Ngai, Quang Nam, Kon Tum, Thua Thien Hue In Thua Thien Hue, species of genus Sewellia usually reside in headwater streams in Nam Dong, Phu Loc, Huong Tra, A Luoi district So far, loaches have been collected from the wild to supply the domestic and foreign aquarium industry Fishing and rearing these species are facing to obstacles as high mortality rate Despite being considered for ornamental purpose, these species have not been bred, reared yet and rarely studied Most of previous studies on these fish focused on classification and distribution There is no study about biological characteristics of hillstream loaches reported in Thua Thien Hue, Vietnam or in the world Therefore, the project “Biological characteristics and rearing loaches (Sewellia spp.) distributed in Thua Thien Hue” is necessary to build up the biological database and tend to accomplish the rearing process for species of this genus in future 1.2 Objectives and scopes Objectives: Examine biological characteristics of two species of Sewellia distributed in Thua Thien Hue; Experimentally breed and examine effects on some factors on these two species in rearing Scopes: The study was conducted on two species of loach distributed in Thua Thien Hue, Vietnam 1.3 Study contents - Examine species composition, morphological characteristic, distribution and habitat of species of genus Sewellia distributed in Thua Thien Hue province - Examine biological characteristics of two species of loach distributed in Thua Thien Hue province, including feeding, growth and reproduction - Experimentally breed and examine effects on some factors on these two species in rearing 1.4 New contributions of the thesis i Clearly defined scientific name of tiger hillstream loach (Sewellia lineolata) and spotted butterfly loach (Sewellia albisuera) in Vietnam ii Defined biological characteristics of tiger hillstream loach and spotted butterfly loach distributed in Thua Thien Hue, including habitat, feeding, growth and reproduction v Confirmed that RH-LHA3 can be used to stimulate spawning of tiger hillstream loach and spotted butterfly loach Heat shock can be used to stimulate spawning of tiger hillstream loach but not for spotted butterfly loach vi Confirmed that tiger hillstream loach and spotted butterfly loach cannot adapt to stationary water environment and temperature higher than 30 oC Powder industrial feed can be used to feed two studied fish species in rearing CHAPTER METHODOLOGY 2.1 Study period and site - Study period: From 01/2016 to 12/2018 - Study sites: + Collected samples and did field trips at rivers and streams in Thua Thien Hue province + Analysed samples at the laboratory of fisheries faculty, Hue university of Agriculture and forestry and some laboratories of Hue university of Medicine and Farmacy, Hue university of Science, Institute of Biotechnology, Hue university 2.2 Study subject Two species belonging to genus Sewellia distributed in streams and rivers in Thua Thien Hue province 2.3 Methods 2.3.1 Determine species composition, classification characteristic, distribution and habitat of loaches in Thua Thien Hue We investigated sites in Thua Thien Hue province, including Nam Dong, A Luoi, Phu Loc, Huong Tra, Phong Dien, Huong Thuy district and Hue city Fish species of genus Sewellia were collected and identified by comparing morphological charateristics according to method reported by Kottelat (1994) and Freyhof (2003) After classified by morphological method, fish were identified by using molecular genetic method according to Kumar et al (2007) Distribution of studied fish species was determined based on field surveys and GPS technique Water environmental parameters as current, DO, pH were examined by using professional equipments; alkalinity, amount of nitrogen, phosphor were determined at laboratory according to method described by Baird et al (2017); bed characteristic and light were visually assessed 2.3.2 Determine biological characteristics of two species of loach in Thua Thien Hue Biological characteristics of two species of loach include feeding, growth and reproduction Feeding of fish was examined based on samples collected in rivers and streams of Nam Dong district in Thua Thien Hue province After collecting, samples were preserved in formalin 10% to analyse in laboratory later Characteristics related to feeding of fish include digestive tract structure, relative length of the gut, fullness, natural food of fish Digestive tract characteristics including mouth, teeth, gill, esophagus, stomach and intestine were examined according to method described by Nikolsky (1963) The relative length of the gut was determined using method of Al-Hussaini (1949) Fullness of fish was assessed according to level scale described by Kock et al (1994); gastro-somatic index (Ga.SI) was calculated according to Desai (1970); Natural food of fish were analysed using numerical method of Hynes (1950), Pham Thanh Liem and Tran Dac Dinh (2004) Natural food of fish were identified using published documents of Ruppert and Barnes (1994), Thai Tran Bai (2008), Pham Hoang Ho (1972), Duong Duc Tien and Vo Hanh (1997), Wehr and Sheath (2003), and Bellinger and Sigee (2010) Growth characteristic and population fluctuation of two fish species were examined on 7258 individuals that included growth parameters, parameters related to population fluctuation and correlation between length and weight of fish The length and weight of fish were defined according to description of Pravdin (1973) The parameters as L, K, t0 were calculted according to description of Gayanilo and Pauly (1997) Population fluctuation parameters were calculated according to description of Pauly (1984) Correlation between length and weight of fish was analysed according to description of King (1995) The growth coefficient (K) was calculated according to method of King (1995) Based on b index above, it can be seen that length of fish body is bigger than horizontal of fish body for female and opposite for male However, this difference is not so much Based on b index we defined condition factor (CF) of studied fish The results showed that CF of spotted butterfly loach was highest in March and September while CF of tiger hillstream loach was high in February, March, July, August and September (Figure 3.12) Figure 3.12: Condition factor A Spotted butterfly loach, B Tiger hillstream loach Condition factor is one to assess weight increment level compared to length Quick weight increment may be due to weight increase of gonad in maturation stage or strong feeding of fish because of abundance of food in the environment (King, 1995) The strong increase of CF at times as seen in Figure 3.12 was consitent with fullness of fish recorded 3.2.3 Reproductive biology a) Sex and male:female ratio Two studied fish species can be identified sex based on morphological characteristics For tiger hillstream loach, the male had angular frontal head (like a trapezoid) (Figure 3.13C) while this part of female was round (Figure 3.13D) Seen from the dorsal surface, the designs of male was large that forms clear yellow-brown pieces, especially in the base of dorsal fin (Figure 3.13A) Meanwhile, the 21 designs of female was nearly round, small, darker and regularly distributed throughout the back (Figure 3.13B) Figure 3.13: Sex identification A, B - Designs on the back of male and female of tiger hillstream loach respectively; C, D - Head shape of male and female of tiger hillstream loach respectively; E, F - Head shape of female of spotted butterfly loach; G, H - Head shape of male of spotted butterfly loach For spotted butterfly loach, clearest character to identify male and female is shape of frontal head that was round for male (Figure 3.13G, 3.13H) and pointed and angular for female (Figure 3.13E and 3.13F) Analysing 3719 individuals of tiger hillstream loach and 3382 individuals of spotted butterfly loach showed that number of female was higher than that of male in population in study sites Specifically, ratio of male:female was 0,83 for spotted butterfly loach and 0.76 for tiger hillstream loach This ratio changed between months and size classes of fish For young fish class, number of female was higher than that of male but opposite for bigger fish class (size class of > 55mm for tiger hillstream loach and > 75 mm for spotted butterfly loach) 22 b) Fatness Clark fatness of tiger hillstream loach varied from 1.08 to 1.66 through months and Fulton fatness was from 1.48 to1.92 (Figure 3.14) Both Clark and Fulton fatness varied through months and focused on two periods Fatness of fish increased from January to March and dramatically decreased in April in first period For second period, fatness of fish strongly increased from June to August Thus, it can be said that tiger hillstream loach strongly absorbs nutrient in JanuaryMarch and July-August Figure 3.14: Monthly fatness variation of loaches A Tiger hillstream loach, B Spotted butterfly loach Fulton fatness of spotted butterfly loach varied from 1.56 to 2.00 and Clark fatness was from 1.37-1.68 Fatness of this fish was highest in March and September and nearly stable in other months Thus, it can be said that spotted butterfly loach strongly absorbs nutrient in March and September c) Development stages of gonad Examining 360 individuals of tiger hillstream loach and 320 individuals of spotted butterfly loach showed that gonad development of two species is similar We observed development stages of ovary and seminal vesicle (stage II, III, IV, VI) Development stages of ovary: The ovary of stage II was small, pink; eggs were small, with average diameter of 99.89±36.04 µm for tiger hillstream loach and 94.58±34.50 µm for spotted butterfly loach 23 The ovary of stage III clearly increased in size and weight, light yellow, and easy to visually discriminate from seminal vescle; average diameter 326.46±129.29 µm for tiger hillstream loach and 375.54±119.45 µm for spotted butterfly loach The ovary of stage IV occupied almost abdomen sinus; average diameter 495.43±79.09 µm for tiger hillstream loach and 513.38±83.51 µm for spotted butterfly loach The ovary of stage VI was small in size and wrinkled; there were mostly young eggs and some ripe eggs in ovary; traces of ovary follicle were seen under microscope Development stages of seminal vesicle: Seminal vesicle of stage II was very small, white and difficult to find when dissecting fish; spermatogonia and producing spermatozoa were found when observed under microscope Seminal vesicle of stage III was light pink to ivory-white; when observed under microscope, we can see spermatids, a bit of spermatozoa, spermatogonia, spermatozoa of level I, II Seminal vesicle of stage IV was large, milky and easy to visually discriminate from ovary; when observed under microscope, we can see a lot of spermatozoa and spermatozoa of level I, II, bigger spermatogonia Seminal vesicle of stage VI was small, milky and difficult to discriminate from seminal vesicle of stage II; when observed under microscope, we can see the empty vesicles in which there is some spermatozoa and spermatids d) Temporal gonad development 1200 individuals of spotted butterfly loach (600 males 600 females) were examined and there was variation of maturation level of ovary and seminal vesicle throughout the year (Figure 3.15) 24 Figure 3.15: Monthly variation of ovary (A) and (B) development stages of spotted butterfly loach Ovary and seminal vesicle of stage IV of spotted butterfly loach were found in all months but peaked in two major periods For females, matured fish ratio was high from January to April (highest in February and March, with 42% and 44% in number of fish having ovary of stage IV, respectively) and August (with 24% in number of fish having ovary of stage IV) For males, matured fish ratio was high from January to May and from July to August Ovary and seminal vesicle of stage IV of tiger hillstream loach were also found in all months but peaked in two major periods For females, matured ovary ratio was high from October to January (highest in January, with 32%) and from April to June (highest in May, with 58%) (Figure 3.16) Figure 3.16: Monthly variation of ovary (A) and testis (B) development stages of tiger hillstream loach 25 For males, matured seminal vesicle ratio was high from October and from February and from April to June The presence of fish having matured gonads in all months indicates that two studied fish can spawn throughout the year, with the peak in January –April and August for spotted butterfly loach and December-January and April-June for tiger hillstream loach e) Gonado-somatic index (GSI) Because size of seminal vesicle is very small and difficult to weigh, so we only examine GSI of female fish (Figure 3.17 and 3.18) GSI (%) A 2 10 11 12 Month GSI (%) B 2 10 11 12 Month Figure 3.17: Gonado-somatic index of female loaches A Tiger hillstream loach, B Spotted butterfly loach GSI of studied fish clearly varied GSI of ovary of tiger hillstream loach was high in April-June (highest in May, with 7.18%) 26 and November-January (highest in January, with 4.87%) For spotted butterfly loach, GSI of ovary was high in January-April (highest in February-March) and July-August g) Fecundity To assess the fecundity of tiger hillstream loach, 28 individuals having total length from 40.24 mm to 64.33 mm were examined The fecundity of fish was defined according to description of Hunter et al (1992) (only counted ripe eggs - stage IV) (Table 3.5) Table 3.5: The fecundity of tiger hillstream loach Group Number of fish Total length (mm) Body weight (g) Absolute fecundity (eggs) Relative fecundity (eggs/g) 11 47,59±3,02 Average 10 28 53,20±2,09 62,07±1,72 53,21±6,22 2,22±0,34 227,91±92,27 101,04±30,90 2,98±0,30 4,41±0,22 3,03±0,92 354,60±117,35 380,14±210,27 311,21±149,41 117,67±33,30 85,00±43,73 102,97±36,24 Absolute fecundity of tiger hillstream loach was from 227.91 to 380.14 eggs and relative fecundity of fish was from 85.00 to117.67 eggs/g The relative fecundity of big fish class was lower than that of small fish class The relative fecundity was highest in size class of 53.21 mm The fecundity of spotted butterfly loach was higher than that of tiger hillstream loach Average absolute fecundity of spotted butterfly loach was 655.13 eggs and average relative fecundity was 116.90 eggs/g (Table 3.6) Table 3.6: The fecundity of spotted butterfly loach Number of fish Total length (mm) 56,79±1,56 14 68,14±0,51 80,21±2,39 Average 30 67,24±9,56 Group Absolute fecundity (eggs) 319,56±144,09 Relative fecundity (eggs/g) 105,08±36,01 5,44±0,56 641,00±228,00 118,82±41,42 8,38±1,88 1056,50±590,36 126,82±59,28 5,48±2,27 655,13±431,48 Body weight (g) 2,99±0,53 27 116,90±44,48 Proportion mature Proportion mature The relative fecundity of big fish class of spotted butterfly loach was higher than that of small fish class Size class of 80.21 mm total length had the highest relative fecundity (126.82 eggs/g) 4.6.7 The size at first maturation of fish (Lm) Analysing the gonad of 227 males and 183 females showed that the size at first maturation of male and female tiger hillstream loach was 45.04 mm and 44.39 mm, respectively (Figure 3.18) (A) (B) Total length (mm) Total length (mm) Figure 3.18: The size at first maturation of tiger hillstream loach A - Male tiger hillstream loach; B - Female tiger hillstream loach Proportion mature Proportion mature Similarly, we analysed 514 males and 368 females of spotted butterfly loach to define the size at first maturation (Figure 3.19) (A) Total length (mm) (B) Total length (mm) Figure 3.19: The size at first maturation of spotted butterfly loach A - Male spotted butterfly loach; B - Female spotted butterfly loach 28 As seen in the Figure 3.19, the size at first maturation of male and female spotted butterfly loach was 55.88 mm and 54.78 mm, respectively Thus, it can be seen that the size at first maturation of spotted butterfly loach was bigger than that of tiger hillstream loach 3.4 The experimental breeding and rearing 3.4.1 The experimental breeding a) Stimulate fish to spawn by using hormone LH-RHA3 Based on studies about breeding of freshwater fish of researchers as Ly Van Khanh et al (2013), Nguyen Tuan Hiep and Pham Anh Tuan (2014), Pham Thanh Liem et al (2015), we used different doses of LH-RHA3 (50 µg/kg body weight, 100 µg/kg body weight, 150 µg/kg body weight and 200 µg/kg body weight) combined with 10 mg DOM to stimulate spawning of spotted butterfly loach and tiger hillstream loach There were 30 males and 30 females for each treatment Table 3.7: Experimental breeding of tiger hillstream loach using hormone LH-RHA3 Treatment ĐC Dose (µg Number of Affecting LRHA3/kg female alive after time body weight) injected (fish) (hour) 20 Spawning Fertilization Hatching rate female rate rate (%) (%) (%) 0 NT1 50 18 0 0 NT2 100 20 7,83 25,00±5,00 49,30±1,22 39,41±3,23 NT3 150 18 7,83 44,44±5,56 49,37±4,42 39,26±3,06 NT4 200 19 7,17 56,14±8,04 46,50±3,42 39,10±3,99 There was clear difference of spawning ratio of fish between treatments (p < 0.05) Tiger hillstream loach did not spawn in control treatment and treatment (dose of 50 µg/kg body weight) For all doses of 100 µg/kg body weight, 150 µg/kg body weight and 200 µg/kg body weight, there were females spawning, with the highest spawning ratio of fish in treatment of dose of 200 µg/kg body weight (56.14%) Fertilization rate and hatching rate were also different between treatments but not significant (p > 0.05) Affecting time of hormone 29 was 7,17-7,83 hours and shortest in treatment of 200 µg/kg body weight (7.17 hours) For spotted butterfly loach, just dose of 150 µg/kg body weight and 200 µg/kg body weight was effective for spawning of fish Fertilization rate and hatching rate were not different between these two treatments Table 3.8: Experimental breeding of spotted butterfly loach using hormone LH-RHA3 Treatment ĐC NT1 NT2 NT3 NT4 No of Dose (µg female Affecting Spawning LRHA3/kg alive Fertilization Hatching rate time female rate body after rate (%) (%) (hour) (%) weight) injected (fish) 30 0 0 50 28 0 0 100 22 0 0 150 20 8,08 16,67±7,64 44,05±1,23 39,31±2,52 200 20 7,58 18,33±2,89 43,74±3,31 38,84±3,97 b) Stimulate fish to spawn by using heat shock Initial water temperature was 23 ºC and it was increased to 26 ºC (within 40 minutes) and 29 ºC (within 60 minutes) Bảng 3.9: Experimental breeding of tiger hillstream loach using heat shock Tr eat me nt tbđ (ºC ) tsốc (ºC ) 𝒯sốc (minute ) No of fish Affecting time (hour) Spawning female rate (%) Fertilization rate (%) Hatching rate (%) 23 23 - 20 - - - 23 26 40 20 16,20 36,67±7,64 52,22±2,40 48,62±4.22 23 29 60 20 16,00 41,67±5,77 45,78±5,03 45,10±2,30 Note: tbđ: initial temperature; tsốc: shock heat; 𝒯sốc: time of heat shock; n: number of female The results showed that both levels of heat shock were effective for spawning of tiger hillstream loach Affecting time of treatment (26 ºC) and treatment (29 ºC) was 16.2 hours and 16 hours, respectively 30 Spawning rate of fish in treatment was higher than that in treatment 2, however, fertilization rate of treatment was higher than that of treatment The similar experiment was also conducted on spotted butterfly loach but there was not any effectiveness for spawning of this fish species c) Characteristics of egg and embryo development of tiger hillstream loach After spawning, eggs were hatched in spawning tanks with DO amount of 6.37±0.44 mg/L, pH of 7.38±0.2, temperature of 27.40±0.6 and sand-gravel bed Observing the spawning of fish showed that fish eggs were usually sticked on 3-10cm gravels that were smooth, not angled The eggs began segmenting after 30 minutes from spawning; blastula was formed after hours and gastrula was formed after hours; eggs were hatched after 26 hours and yolk was completely absorbed after 52-58 hours from hatching The fries were very difficult to see because of its small size and transparent white color They had the big yolk sack at abdomen bottom and the back after head had black spots when observed under microscope d) Experimental rearing of 10-60 day old fish Because the bed of hatching tanks is sand and gravel and size of fries is very small, so fish can be only collected at 10th day after hatching to conduct the experiment At this time, fish body was light black and easy to distinguish from the bed Thus, the rearing experiment is only carried out when fish are 10 days old Food used in the experiment were dry Spirulina and industrial powder feed Absolute and relative growth rate of length of spotted butterfly loach gradually decreased from 10 to 60 days of rearing while absolute and relative growth rate of weight of fish gradually increased to 60 days of rearing Different from spotted butterfly loach, absolute and relative growth rate of length of tiger hillstream loach strongly increased from day 10 to day 30 of rearing and decreased from day 30 to day 60 31 Similarly, absolute and relative growth rate of weight of this fish species also increased from day 20 to day 30 and reduced from day 30 to day 60 3.4.2 Experimental rearing Rearing tiger hillstream loach and spotted butterfly loach in aquarium is not easy for culturists because in nature they usually inhabit in areas having strong water currents, high dissolve oxygen, low temperature and they are stick algae eater Therefore, to support acclimation and aquarium rearing, factors as food, temperature and dissolve oxygen amount were selected to the experiments Other factors, in general, are suitable for growth and development of fish a) Effects of food on fish Dry Spirulina and industrial powder feed were used in the experimental rearing After weeks of rearing, survival rate of fish was 100% for all treatments This indicates that fish can adapt well to new food although their natural food is stick algae Therefore, culturists can use dry algae and industrial powder feed to feed these fish species in aquarium rearing Besides of examining survival of fish, color variation and swimming activity of fish were also observed but there was no difference between treatments b) Effects of temperature on fish Three levels of temperature (26 ºC, 29 ºC 32 ºC) were examined for two studied fish species After weeks of rearing, survival of fish at 26 ºC was highest (100% for tiger hillstream loach and 98,89% for spotted butterfly loach) At 29 oC, survival of fish was 98.89% for tiger hillstream loach and 97.78% for spotted butterfly loach However, at 32 oC, there was no fish alive after days of rearing for both studied species We found that at 29 oC just some fish died in the first week of rearing and they survive well after that but at 32 oC body color of fish became light and fish lost mucus and died after one day of rearing There was no difference of body color and activity of fish between 26 oC and 29 32 o C during weeks of rearing The results showed that two studied fish can be cultured at 26-29 oC c) The experiment of rearing type There are three types of rearing freshwater ornamental fish that includes rearing in tanks with strong water current and filter, rearing in tanks with slight water current and filter, and rearing in tanks with stationary water In this study, two studied fish were experimentally cultured in all these types of rearing The results showed that survival rate of both species was highest (100%) in tanks with strong water current and filter (DO from 6.787.39 mg/L) In tanks with slight water current and filter (DO from 3.84-4.55 mg/L), survival rate of fish was 97.78% for tiger hillstream loach and 96.67% for spotted butterfly loach In the tanks with stationary water, spotted butterfly loach completely died after days of rearing while tiger hillstream loach still survived 8% after rearing weeks There was not any difference of body color and swimming activity between two types of flowing water rearing Fish in these treatments still kept natural color and normal activities Thus, it can be seen that both tiger hillstream loach and spotted butterfly loach can be raised in tanks with water current and filter (DO from 3.84-7.39 mg/L) 33 CHAPTER CONCLUSION AND SUGGESTION 5.1 Conclusion i There are two species of loach in streams in Thua Thien Hue province that are tiger hillstream loach (Sewellia lineolata) and spotted butterfly loach (Sewellia albisuera) ii Tiger hillstream loach and spotted butterfly loach are distributed in headwater streams where have strong water currents, sand-gravel bed, high amount of dissolve oxygen, neutral pH, low total amount of alkalinity, nitrogen and phosphor, iii Tiger hillstream loach and spotted butterfly loach are gnawers and their major food are microalgae, of which Bacillariophyta is dominant iv The reproductive activities of two studied fish species occurs throughout the year The major spawning season focuses in AprilJune and November-January for tiger hillstream loach and in JanuaryApril and August for spotted butterfly loach v Hormone LH-RHA3 can be used to stimulate spawning of tiger hillstream loach (with dose of 100, 150 200 µg/kg body weight) and spotted butterfly loach (with dose of 150 200 µg/kg body weight) Heat shock can be used to stimulate spawning of tiger hillstream loach but not for spotted butterfly loach vi Industrial feed can be used to feed tiger hillstream loach and spotted butterfly loach in aquarium rearing Both studied fish species can be cultured in tanks with water current, filter and temperature ≤29 ºC 34 5.2 Suggestion i Study to build and accomplish breeding process of tiger hillstream loach and spotted butterfly loach to supply the domestic and foreign aquarium industry ii Study to build rearing process of broodstock of tiger hillstream loach and spotted butterfly loach to ensure source of broodstock for breeding 5.3 Recommendation Industrial feed can be used to feed tiger hillstream loach and spotted butterfly loach in aquarium rearing Temperature suitable for tiger hillstream loach and spotted butterfly loach in aquarium rearing is ≤ 29 oC Rearing tanks with flowing water and aeration are suitable for tiger hillstream loach and spotted butterfly loach LH-RHA3 with dose of 100, 150 200 µg/kg body weight and with dose of 150 200 µg/kg body weight, combined 10mg DOM can be used to stimulate spawning of tiger hillstream loach and spotted butterfly loach, respectively Heat shock can be used to stimulate spawning of tiger hillstream loach 35 ... hillstream loach (Sewellia lineolata Valenciennes, 184 6) and spotted butterfly loach (Sewellia albisuera Freyhof, 200 3) According to Vu Cam Luong (200 8), tiger hillstream loach and spotted butterfly loach... females of spotted butterfly loach to define the size at first maturation (Figure 3.1 9) (A) Total length (mm) (B) Total length (mm) Figure 3.19: The size at first maturation of spotted butterfly loach... hillstream loach (Sewellia lineolata) and spotted butterfly loach (Sewellia albisuera) in Vietnam ii Defined biological characteristics of tiger hillstream loach and spotted butterfly loach distributed