Studies On Reproductive Biology And Artificial Propagation Of Loach

The loach (Misgurnus anguilicaudatus), an autochthonous fish of china and other Asian countries, has reeently shown a great potential in the aquaculture of China because of overfish and environmental pollution, Natural loach resources declined rapidly after major natural disasters from 2006 to 2007 in chongqing area. Loach market demand is gradually increasing and loach breeding has entered into rapid development stage as people realize loach high nutritional value. However, loach larval appear large-scale death in the early life history,but the main reason is still not clear so far. Above all hinder the further development of loach breeding.On the basis of understanding loach reproductive biology, we have conducted the research to its reproductive biology, artificial reproductive technology and the key link of fry cultivation technologies. In order to establish the technology system of loach in artificial propagation, it provides theoretical basis for this system. 1. Loach fecundityThe individual absolute fecundity ranged from 1,000,0 to 2,000,0 eggs and ralative fecundity ranges from 450-600 eggs per gram in the weight of loach from 20 grams to 30 grams,the individual absolute fecundity of Paramisgumus dabryanus (Sauvage) was a little more than Misgurnus anguilicaudatus.2. Loach embryonic development observationFrom 16℃to 18℃, we observed the loach embryonic development process. The observation results showed that the loach eggs had normal development. The whole development process could be devided into 30 developmental periods. From fertilization to its incubation period, it needed 61.5 hours. We classified Loach larval growth into four times, lying stage, vertical movement stage, hangs stage and balance swimming stages.3. The effect of different injection hormone species, dose and ratio of HCG,LHRH-A2 and complex hormones H CG+LHRH-A2 on the spawning effect of loachThrough 27 times of contrast experiments and repeated experiments, we researched the effect of different injection hormone species, dose and ratio of hormone on the spawning effect of loach.The research results showed that:(1).Only injection LHRH-A2 or HCG both could achieve the purpose of Induced spawning; (2). The optimum injection dose of HCG for spawning effect of loach was 200 IU/tail; (3). The optimum injection dose of complex hormones HCG and LHRH-A2 for spawning effect of loach was 200 IU/tail and 2μg/tail; (4).injection of complex hormones had the best effect.4. The effect of environmental factors on inducted spawning of loachThrough different of Induced spawning contrast experiments, we researched the effect of environmental factors on inducted spawning of loach. The research results showed that:(1). The best hormone injection time is 6:00pm; (2). From 16℃to 18℃water, hormone injection can have better effect of Induced spawning, The best water temperature is from 24 to 28℃. It is closely related between Loach larval growth and temperature. Belowing the 20℃water temperature, Loach larval grew more slowly, but above 20℃, the growth rate has been obviously paced up.There were little change with the rising of water temperature. (3). The best spawning depth of water is 60cm and the best Incubation depth of water is 30cm..5. The effect of different hatch methods on incubationWe have studyed the effect of different hatch methods on hatching, including Static water cage hatch, running water cage hatch, aerating cage hatch, Static water cylinder hatch, running water cylinder hatch, aerating cylinder hatch.The research results showed that running water cage hatch and aerating cage hatch have better effect of incubation, the rate of hatch is the highest.6. Loach larval initial baits and the best feeding timeWe have studyed the effect of loach larval initial baits and the best feeding time on growth, the research results showed that:(1).the best loach larval initial baits was composite nutrition of plankton, such as plankton and egg yolk and so on; (2).the best feeding time was the third day after hatching.7. The effect of different culture methods on survival rateWe have studyed the effect of different culture methods on survival rate,including breeding barrels,hatch tank,cage,cement pond and pond. The research results showed that:(1). All the culture methods could obtain good effect In the suitable water quality conditions; (2). Breeding barrels and hatch tank culture methods had better effect in reasonable breeding density,and the survival rate reached above 60%;(3). Pond culture method had good effect In outdoor, and the survival rate reached about 55%.To solve the problem of insufficient supply of loach larval, The research conducted 27 times artificial propagation experiment, the induction rate reached above 90%, the hatching rate reached above 80% and the survival rate reached above 60%. It producted loach younger fish about 5,000,000,0 tails,and meeted the needs of the project that products 500kg rice and 1,000 yuan loach benefits in half.