Study On The Cultivation Biology Of Four Endemic Fishes In The Plateau

Influenced by natural and human factors, the resources of endemic fishes declined sharply, and some of endemic fishes were endangered in the plateau. Oxygymnocypris stewartii Lloyd, Schizothorax oconnori Lloyd, Schizothorax waltoni Regan and Brachymystax lenok tsinlingensis Li have significant regional representation and evolutionary characteristics. To investigate the cultivation biology of four endemic fishes in the plateau, artificial breeding, seeding cultivation, enhancement and releasing were researched in the Tibet and Shaanxi plateau region from June 2009 to December 2015, respectively. Also these were important and urgent methods to protect and recover resources of endemic fishes in the plateau. The related problems of food selection, feeding model, disease control, artificial breeding and cultivation etc. were studied on four endemic fishes in the plateau. The main results are as follows:1.The effects of three different diets on the growth and survival of three native fish larvae(Oxygymnocypris stewartii Lloyd, Schizothorax oconnori Lloyd and Schizothorax waltoni Regan) were conducted in Tibet. Artemia nauplii, the special diet for larvae, and fish meal were chosen for the diets of all the three fish larvae. The initial length of 13.29±0.52 mm for O. stewartii larvae, 12.29±0.44 mm for S. oconnori larvae, and 15.81±0.50 mm for S. waltoni larvae were chosen for the feeding experiment. The experiment periods for the three fish larvae were 25 d, 25 d and 15 d, respectively. The results showed that S. oconnori larvae and S. waltoni Regan larvae fed on the special diet for larvae had a significantly higher average and total length and survival rate, when compared with those fed on the other diets. O. stewartii larvae fed on the special diet for larvae had a significantly higher average and total length than those fed on the other diets, while O.stewartii larvae fed on Artemia nauplii had a significantly higher survival rate than those fed on the other diets.2.To investigate the effects of the different diets on growth and survival of the larva and juvenile stages of Brachymystax lenok tsinlingensis Li were recorded during their early development. Natural food, living food, combinative feed and mixed feed were used to feed the larvae and juveniles of B. lenok tsinlingensis for 65 days in the experiment. The results indicated that the highest specific growth rate(SGR) and weight growth rate(WGR) of combinative feed were 0.99 % and 487.82 % respectively. Fish fed with natural food showed highest survival rate(81.67 %) at the end of experiment; fish fed with living food showed lowest SGR, WGR and survival rate, while no significant difference was observed with mixed feed(P > 0.05), and it showed significant difference with combinative feed and natural food(P < 0.05). B. lenok tsinlingensis showed obvious preference to living food and natural food, fish fed with living food showed excellent growth and survival rate at the larva stage, moreover, stabilization growth and survival occurred in natural food groups during larva and juvenile stages. Therefore, phase and mix feeding is recommended for B. lenok tsinlingensis feeding in the early life stage.3.To evaluate the effects of starvation on the feeding, growth parameters and survival rate, the larvae of Schizothorax waltoni were exposed to different feeding schedules under laboratory conditions in the breeding farm of Schizothoracinae fishes in Tibet, China. S. waltoni larvae established first feeding 6 days after hatching(DAH) at 12°C. Starved larvae showed similar feeding rate as the fed larvae before 28 DAH, and reached the irreversible starvation age at 30 DAH. Normal development was observed in both the fed and starved groups before 17 DAH, and subsequently the starved larvae showed reverse growth. The high daily mortality occurred from 7 to 12 DAH in the fed group, while the high daily mortality was detected during 29~33 DAH in the starved group. Based on the irreversible starvation age and the first feeding time, initially of offering extermal food to S. waltoni larvae, the optimal time should be at 12~13 DAH. The relationship between total length and body weight of S. waltoni can be formulated In the round plastic basin group, the high daily mortality occurred from 20 to 25 d, while the high daily mortality(9 %) was detected at 20 d. Otherwise,the larvae in the aquarium group has no obvious peak of death, and cumulative mortality is 8.67 % throughout the experiment. Therefore, under the same density, the S. oconnori larvae have obvious cluster effect, fast growth and stable survival rate in cement pool.5.The larvae of two different Schizothorax species, S. oconnori Lloyd and S. waltoni Regan, were exposed to copper for 264 h in a series of static toxicity tests. The weight and length(Mean±SD) for S. oconnori and S. waltoni were 14.79±0.63 mg and 12.93±0.81 mm, and 17.89±0.31 mg and 13.53±0.45 mm, respectively. At a copper concentration of 3.2 mg/L, both species became uneasy and tried to avoid the toxic water by swimming fast. They dove into the bottom of the glass tank and then swam to the top trying to gulp the air, and repeated this movement. Ultimately, the fish were exhausted, and swam helically with jerky movements at the bottom of the tank after suffering from physical stimulation. After 8 h exposure, all fish of the two species died, which was characterized by morphological deformity, protruded egg yolks, and whitened body coloration. There were nodules of blue crystals on the surface of the body. However, as the copper exposures decreased, the morphological and avoidance responses also decreased. The mortality rates of these two species increased as the exposure concentrations increased and the exposure time was prolonged. Estimated 96 h median lethal concentration(LC50) values were 0.31 and 0.28 mg/L for the two species, respectively. The safe concentration(SC) value was significantly higher for S. oconnori(0.21 mg/L) than for S. waltoni(0.05 mg/L). These findings indicated that larvae of these species were sensitive to copper, and that both species may be suitable for use as a local biomonitors of copper pollution in the high altitude environment. However, copper drugs used carefully in aquaculture for therapeutic purposes.6.This study was conducted to investigate B. lenok tsinlingensis spermatozoa cell morphology and ultrastructure through scanning and transmission electron microscopy. Findings revealed that the spermatozoa can be differentiated into three major parts: a spherical head without an acrosome, a short mid-piece, and a long, cylindrical flagellum. The mean length of the spermatozoa was 36.11±2.84 μm, with a spherical head length of 2.78±0.31 μm. The mean anterior and posterior head widths were 2.20±0.42 μm and 2.55±0.53 μm, respectively. The nuclear fossa was positioned at the base of the nucleus that contained the anterior portion of flagellum and a centriolar complex(proximal and distal centrioles). The short mid-piece was located laterally to the nucleus and possessed just one spherical mitochondrion with a mean diameter of 0.65±0.14 μm. The spermatozoa flagellum was long and cylindrical, and could be separated into two parts: a long main-piece and a short end-piece. The main piece of the flagellum had short irregular side-fins. The axoneme composed the typical ?9+2? microtubular doublet structure and was enclosed by the cell membran e. This study confirmed that B. lenok tsinlingensis spermatozoa can be categorized as teleostean “Type I” spermatozoa; ?primitive? or ?ect-aquasperm type? spermatozoa.7.The present study was designed to evaluate the use of microsatellite markers to identify parentage in B. lenok tsinlingensis, an endangered species of fish. Computer simulations showed that when no parent information was available, or when information was only available from one parent, then the exclusion probability ranged from 23.6 % to 45.1 %, and from 25.9 % to 52.4 %, respectively; combined exclusion probability for the nine loci investigated were 98.48 % and 98.94 %, respectively. However, under real circumstances, a breeding experiment with known parental and filial information resulted in 91.28 % of individuals being exclusively assigned to their correct parent pair. The paternity test kit of B. lenok tsinlingensis was developed. Our data demonstrates that microsatellite-based parentage assignment approach established here can fully replace physical tags to retain information on genealogical relationships among individuals over multiple generations and avoid inbreeding in B. lenok tsinlingensis. The microsatellite-based parentage assignment is a reliable means with which to obtain information pertaining to genealogical relationships and could therefore be of benefit in the genetic conservation of this species.