tóm tắt luận án study on the biological characteristics and induced spawning of spotted scat

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tóm tắt luận án study on the biological characteristics and induced spawning of spotted scat

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MINISTRY OF EDUCATION AND TRAINING CAN THO UNIVERSITY LY VAN KHANH STUDY ON THE BIOLOGICAL CHARACTERISTICS AND INDUCED SPAWNING OF SPOTTED SCAT (Scatophagus argus Linnaeus, 1766) Specialization: Marine/Brackishwater Aquaculture Field of Study Code: 62 62 70 05 Dissertation of Doctor Degree in Aquaculture Can Tho, 2012 The study carried-out at: - Ngoc Hien and Nam Can district, Ca Mau province - College of Aquaculture and Fisheries, Can Tho University Supervisors: A/Prof Dr Nguyen Thanh Phuong A/Prof Dr Tran Thi Thanh Hien Examiner 1: A/Prof Dr Nguyen Tuong Anh Examiner 2: Dr Bui Minh Tam The dissertation will be defensed at the university committee in meeting room of College of Aquaculture and Fisheries, Can Tho University at time of: ….… hr ….… date …… month …… year 2012 The disseratation is available in Libraries:  Library Center of Can Tho University  College of Aquaculture, Can Tho University Introduction Background and problem statement Viet Nam has a great potential for marine/brackish-water aquaculture development Recently, marine/brackish-water aquaculture of Viet Nam is likely based on single species and its negative impacts on water environment and disease outbreak have occurred The diversification of farming species in the coastal areas is very important for sustainable development; and few brackish-water fish species has been introduced to farm at pilot scale However, the development of marine/brackish-water species has faced various difficulties, especially hatchery-reared seed supply, which is considered a basis requirement Spotted cat (Scatophagus argus) distributing along the coastal areas is the potential species for aquaculture especially in the Mekong delta However, there are short of seeds in both of wild and hatchery seeds for culture systems Therefore, the biological characteristics and induced spawning of spotted scat fish (Scatophagus argus Linnaeus, 1766) is needed to be studied for developing aquaculture production of this species The Objective of Study - General objective: to find out the biology characteristics to contribute the scientific information or development of artificial propagation of spotted cat; to diversify the aquaculture species and farming systems in the coastal areas; to archive the sustaining development of aquaculture in the Mekong Dleta and Vietnam - Specific objective: to determine the main biology including physiological characteristics, kinds of ganodotropic hormones/and chemicals corresponding with artificial propagation in Spotted cat hatchery; to develop the techniques in nursing Spotted scat from fry to fingerling stage The Contents of Study - The study on the main biology and physical characteristics relating to the reproduction of Spotted cat - The study on the investigation/and use of ganodotropic hormones and chemicals in the artificial propagation reproduction and hatching techniques of Spotted cat - The study on the development of digestive system (intestine) and feeding habits of fry of Spotted cat - The study on nursing Spotted cat from fry stage to small fingerling with different feeds; and nursing small fingerling to fingerling at different salinities The useful outcomes The findings of the research provide basic scientific information of reproductive and physiological biology of spotted cat; and induced spawning and larvae to fry and fry to fingerling rearing The above information will be utilized for the complete development of seed production techniques of the spotted cat, which is important for spotted cat grow-out activities, contribution to diversification of farming species and sustainable development of marine/brackishwater aquaculture in Viet Nam especially in the Mekong Delta New findings of the thesis - Spawning seasons, relative fecundity, egg diameter and embryo development of spotted cat were determined - Relationship between hematological parameters (red blood cell, white blood cell, hematocrit, ), phosphate protein (vitellogenin) concentration and maturation stages of spotted cat were established - Yolk sac size (length and width), larval month size, larval length, yolk sac absorption duration, and larval initial food selection and digestive tract development were found - More especially, technique for induced spawning was successfully found; initial food for newly hatched larvae up to 30 days was identified; and the suitable salinity for nursery of fish from 30 to 60 days was also chosen The above results indicated that the technique of artificial propagation and larval rearing of spotted cat were established and is able to produce mass seeds for grow-out activities, diversification of farming species, and farming models as well The thesis also indicates possibility to close the life cycle of the spotted cat in captive conditions The lay-out of dissertation The dissertation has 163 pages It consists of pages of introduction, literature review 30 pages, methodology 20 pages, results 57 pages, conclusion and recommendation pages, list publication pages, cited references 15 pages and 31 pages of indices Chapter 1: Literature review The literature review focused to investigation of main points following as: - The biology characyeristics of Spotted cat - The physiological characteristics of Spotted cat - The ganadotropic hormones and chemicals corresponding with spotted cat - The imformation relating to the techniques in hatchery of marine/brackish water fishes - Development of intestine system and feeding habits of spotted cat - Natural food and compound feeds used for rearing fry of fish - The issues studied on natural food/ compound feeds and salinity in the nursing marine fishes In the results of the previous studies, the biological characteristics of spotted cat are not studied completely; the hatchery seed production is not successful However, based on the information reviewed the new studies are established to determine the biology characteristics of Spotted cat and find the techniques of hatchery seed reproduction Chapter 2: METHODOLOGY 2.1 Location and time of the study The study was carried-out at Nam Can and Ngoc Hien districts, Ca Mau province; and the hatchery of College of Aquaculture and Fisheries, Can Tho University, from September 2006 to November 2010 2.2 Experiment setting 2.2.1 The sudy on reproductive biology characteristics Thirty spotted cats was collected monthly during 12 months to record the individual weight, sex ratio, the weight of gonad, maturation indexes, female and male ratios, phases of development of gonad and diameter of eggs The relationship among the development of gonads, maturation rate of fish and fat indexes of Fulton and Clark were investigated based on the fish samples collected The weight of fish, standard length, weight of fish without viscera, fat indexes of Fulton and Clark, sex ratios, weight of gonad and the development phases of gonad are monitored Mature broodstocks catched from wild were stimulated for spawning by using gonadotropic hormones and chemicals for recording the spawning capacity, diameter of eggs, development of embryos, size of egg yolk, size of mouths, length of fries 2.2.2 The study on physiological characteristics of spotted cat The collected samples of spotted cat were recorded as six phases of gonad development, weight of fishes, sex ratios, weight of gonads and maturation ratios The blood samples of fishes were collected from the dorsalis by using syringe The blood characteristics analalysed following as number of red blood cells, leukocyte, haemoglobin, ratio of haematocrit, volumm of red blood cell µm3 (MCV), the mean weight of haemoglobin in red blood cell (MHC), concentration of haemoglobin in red blood cell (MHCH), concentration of protein, phosphate in the plasma (Vitellogenin), concentration of protein in muscle and liver 2.2.3 The experiments of spawning stimulation and hatching eggs of spotted cat 2.2.3.1 Study on the maturation culture of spotted cat One-year-old broostocks from hatchery reared fish were grew-out in composite tanks (2 m3 tank) at 15‰ salinity during months The fish was fed twice a day by using 35% protein commercial feeds (Grobest Company) In the experiment, the parameters of water quality were determined such as total amonia nitrogen (TAN), nitrite (N-NO2-), weight of fish, weight of fish gonads, and development of gonad, indexes and matuarion of ratios 2.2.3.2 Study on the kinds and doses uses of gonadotropic hormones and chemicals corresponding with artificial reproduction The mature broodstocks collected from the wild were stimulated for artificial reproduction (Table 2.1) The female broodstocks were injected by times (preparatory and decisive injections), meanwhile the male is injected time at the same time as the decisive injection of female After decisive injection, the activities of the broodstocks were monitored; when the females were ovulating, testises of males were dissected and ground to get the sperms for fertilizing the eggs latter The eggs and sperms were mixed well and hatched in 30‰ salinity water Table 2.1: Kinds and doses of gonadotropic hormones and chemicals use Kind Dose Ovaprim (ml/kg) 0.5 1.0 LHRH-a (µg/kg)+Dom (5 mg/kg) 50 100 HCG (UI/kg) 1,000 1,500 1.5 150 2,000 The parameters were recorded such as the time of hormone responding, the time of oocyte development, ratios of fish ovulating, fertilizered egg, off-pring and heterophyte Gonadotropic hormone injection Spotted cat post-injected female ovulating Testises Sperms and eggs mixing Mature broodstock tank Hatching and larvae nursing tank Fig 2.2: The procedure deneating the artificial reproduction of Spotted cat 2.2.3.3 The effects of salinities on hatching rates The wild mature spotted cat injected ovaprime with dose of mL/kg (see types and doses used in section 2.2.3.2) The eggs and sperms were mixed well and incubated in treatments with 0, 5, 10, 15, 20, 25 and 30‰ of salinities using 15-liter tanks aerated The incubating density was 100 eggs per liter The temperature, pH and hatching rates were recorded 2.2.4 Study on the development of digestion system and feeding habit of fry The newly hatched fries were nursed in the m3 cement tanks with salinity of 25‰; density of 50 fries per liter and aerated condition The fries were fed natural foods with twice a day The natural foods were collected from water of extensive shrimp ponds using phytophankton scope net 2.2.4.1 Study on the development of digestion system of spotted cat From the tanks mentioned above, the fry samples were collected at 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25 and 30-day-old to analyse histology for determining devlopment of enteron system 2.2.4.2 Study on the food selection and consumption of spotted cat The water sample of the tanks metioned above, were taken at 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25 and 30-day-old of fry to determine the quantity and quality of phytoplankton and zooplankton Based on the frequency of occurrence of each species of planktons in the samples to clarify the food section and the consumption of spotted cat 2.2.5 Nursing fry to small fingerling (1-month-old) 2.2.5.1 The nursing fry to 15-day-old fingerling using different feeds The 2-day-old fries were reared in 15-liter tanks at the salinity of 25‰; 50 fries per liter density with treatments of different types of feeds including (i) Chlorella sp.+Rotifer; (ii) Chlorella sp.+Rotifer+ Compound feed (TACB); (iii) Chlorella sp+TACB; (iv) Rotifer; (v) Rotifer+TACB; and (vi) TACB During 15 days of rearing, the fries were fed times daily The water temperature and pH, length, the growth/and specific growth of fish length, and the survival rates of fries were determined 2.2.5.2 The nursing 15 to 30-day-old fingerling using different feeds The 15-day-old fingerlings were grew-out in the 10-liter tanks with 25‰ salinity The experiment has treatments with feeding by different feed stuffs including (i) Rotifer; (ii) Artemia; (iii) Compound feed (TACB); (iv) Rotifer+TACB and (v) Artemia+TACB The fingerlings were fed times per day during 15 days (15-30 day-old) The water quality and the growth of fish were verified by temperature, length, the growth /and specific growth of fish length, and the survival rates 2.2.6 Nursing the fingerling 30 to 60-day-old at different salinities The experiment has seven treatments including 0, 5, 10, 15, 20, 25 and 30‰ salinity Twenty-five fingerlings were nursed in the 50-liter tanks and fed by commercial feeds at the frequency of times per day During 30 days nursing, the water temperature and pH, weight, the growth /and specific growth of fish, survival rates and size distribution of fish were recorded 2.3 Data analysis The collected data were analysed in the differences of means among the treatments using the one-way ANOVA with DUNCAN test (using Excel 2003 and SPSS version 13.00) Table 3.16: Temperature variation in the tanks during eggs incubation process by different salinity levels testing At the Experiment beginning hours hours 12 hours 16 hours 20 hours plots (‰) point 25.5±0.06 25.6±0.00 25.6±0.12 26.7±0.06 26.5±0.06 26.5±0.10 26.1±0.00 26.0±0.06 26.2±0.00 27.4±0.00 27.2±0.00 27.0±0.00 10 25.7±0.00 25.7±0.23 25.7±0.00 26.5±0.06 26.4±0.06 26.4±0.00 15 26.2±0.00 26.1±0.06 26.4±0.06 27.6±0.10 27.3±0.06 27.0±0.06 20 25.7±0.00 25.7±0.06 25.8±0.06 26.6±0.06 26.4±0.00 26.5±0.00 25 26.0±0.06 26.1±0.06 26.4±0.00 27.3±0.36 27.3±0.06 27.1±0.00 30 26.1±0.06 25.8±0.10 25.9±0.00 26.8±0.06 27.2±0.06 26.4±0.12 Table 3.17: pH variation in the tanks during eggs incubation process by different salinity levels testing At the Experiment beginning hours hours 12 hours 16 hours 20 hours plots (‰) point 8.43±0.12 8.27±0.15 8.33±0.25 8.30±0.17 8.30±0.10 8.43±0.21 8.43±0.06 8.30±0.00 8.33±0.06 8.40±0.00 8.23±0.06 8.30±0.00 10 8.20±0.00 8.13±0.15 8.07±0.06 8.07±0.06 8.10±0.00 8.07±0.06 15 8.33±0.06 8.30±0.00 8.30±0.00 8.30±0.00 8.23±0.12 8.30±0.00 20 8.10±0.00 8.13±0.06 8.13±0.06 8.17±0.06 8.23±0.06 8.17±0.06 25 8.30±0.00 8.30±0.00 8.27±0.06 8.30±0.00 8.27±0.06 8.30±0.00 30 8.23±0.06 8.30±0.00 8.23±0.06 8.27±0.06 8.30±0.00 8.23±0.06 3.3.3.2 Results on eggs incubation at the different salinity levels testing The peak of eggs hatching rate reached at 43.3% in the experiment plot with 30‰ of water salinity used, and the hatching rate of this salinity level is significant difference statistically (p

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