| To set up an efficient ecological rice(Oryza sativa) planting mode combined with finless eel(Monopterus albus)and crayfish(Procambarus clarkii)farming, we investgated the effects of different proportions of rice, crayfish, and finless eel,water spinach(Ipomoea aquatica Forsk), Bacillus subtilis, on water quality, the production in this mode, the ecological framing of finless eel and the toxic effects of common pesticides on finless eel. The results indicated that the best ecological model of rice-crayfish-finless eel: finless eel of 1200 individual each mu(25-50 g each individual) 、 crayfish of 3000 individual each mu(5-10 g each individual), surface coverage rate of spinach of 10%, Bacillus subtilis of 100 g each mu. The water eutrophication score of the best model was 70.5, the lowest infall groups. The rice production was 314.0kg each mu, finless eel was 139.6kg each mu, crayfish was 58.1kg each mu, water spinach was 20.3 kg each mu, the output value was 14910.5yuan each mu, the profit was6713.4 yuan, the maximum in all groups. The weight of finless eel which were pregnant was 1.2-1.9liang which was about 67.5% of all finless eel, such size was suitable as female parents When finless eel weighed 3.6 liang or more, the proportion of male finless eel was 87%,which were suitable as male parents. The results showed that the root of water spinach I was the suitable place for finless eel breeding, Both pond and net cage were suitable place for finless eel breeding. 3:3ratio of male and female was the best in the 60 mesh reticulated boxes.The results of acute toxicity of four common non-pyrethroid pesticides in finless eel showed that, the safe concentrations of four pesticides was Avermectin 0.35ul/L, Jinggangmycin 0.282ul/L,Isoprocarb chlorpyrifos 5.534ul/L, Glyphosate ammonium 423.9ul/L.However, it should be avoided using pesticides during raising finless eel.1. The effects of different stocking density of finless eel on water quality and the production benefit in rice-crayfish-finless eel mode;To evaluate the water quality and benefit in different rice-shrimp-eel mode, we raised crayfisha(3000 individual each mu)with three different amount of finless eel-800 each mu(DXS1), 1000 individual each mu(DXS2), 1200 individual each mu(DXS3) in the circular furrow of rice field. The results showed that, with the amount of finless eel increasing, dissolved oxygen value decreased(DXS1 was significantly higher than DXS2 and DXS3, 3.76mg/L 、 2.86mg/L and2.65mg/L respectively); While ammonia nitrogen was increasing(DXS3>DXS2>DXS1, 1.434mg/L、0.817mg/L、0.553mg/L, respectively),the nitrite nitrogen decreased(DXS1<DXS2<DXS3, 0.022mg/L、0.024mg/L、0.033mg/L, respectively); the level of eutrophication gradually increased(DXS1<DXS2<DXS3, 77.5、78.8、82.6, respectively). The high level of eutrophication in DXS3(1200 individual finless eel each mu)showed that high finless eel density would have a negative effect on water quality. But the final output did not decreased in high density group, thus the three kinds of density were acceptable.The results showed that high finless eel density of DXS3(1200individual each mu) would have a negative effect on water quality and increased the level of eutrophication slightly. DXS2 group(1000individual finless eel each mu) resulted in a good production effect and enough ecological benefit, which would be an acceptable mode.The production effect reached 327.4 kg each mu of rice, 142.4kg each mu of finless eel, 43.1kg each mu of crayfish, 14433.9 yuan each mu of output value, 5967.4 yuan each mu of profit.2. The effects of different stocking density of crayfish on water quality and production benefit in rice-crayfish-finless eel mode;According to the result above, we raised finless eel(1200individual each mu) with three different amount of crayfisha: 2000 individual each mu(DXS4), 3000 individual each mu(DXS5), 4000 individual each mu(DXS6) in the circular furrow of rice field. Water p H, dissolved oxygen did not change with three different stocking density of crayfish. In the highest density group, ammonia were lowest(DXS5>DXS4>DXS6, average value was 0.615mg/L、0.583mg/L、0.447mg/L, respectively), dissolved oxygen were high in three groups(DXS5>DXS6>DXS4, the average value was 5.34mg/L 、 5.32mg/L 、4.90mg/L, respectively), nitrite nitrogen was low(nitrite average value of DXS4 0.044mg/L was significantly higher than that of DXS5,0.025mg/L, DXS6 0.016mg/L,). This result maybe caused by the low food utilization rate in low density group, which resulted in the pollution of unused bait, and in return caused the low dissolved oxygen, high ammonia nitrogen, high nitrite nitrogen in the aqutic water. But on the whole, dissolved oxygen in three groups were not very low, the value were higher than 4.90mg/L; the water environment were in moderate eutrophication status. The results above showed that three different groups can guarantee the normal growth of the finless eel and crayfish.Based on the results of water quality and farming benefit, we found that there was no significant effect on the growth of finless eel with different crayfish density and water quality, but a little high density of crayfish can improve the farming benefit. The benefit of the DXS5 group(3000 individual each mu) was better than other groups, indicating that crayfish density was suitable. The production reached 316.5kg each mu of rice, 126.3kg each mu of finless eel, 57.9kg each mu of crayfish, 20.8kg each mu of water spinach, 13866.5yuan each mu of output value, 5969.4 yuan each mu of profit.3. Effects of different water spinach surface coverage on water quality and benefit of rice-crayfish-finless eel mode;We raised finless eel(1200 individual each mu) and crayfisha(3000 individual each mu) in the circular furrow of rice field.Meanwhile, we planted water spinach with different coverage rate(0%,10%, 20%, 30%). Then we found that when the coverage rate of water spinach increased, the dissolved oxygen of water in circular furrow increased, which were 3.38mg/L, 3.62mg/L, 4.85mg/L and 5.04mg/L Meanwhile, the ammonia nitrogen content decreased, which were1.029mg/L, 0.669mg/L, 0.525mg/L and 0.527mg/L. The nitrite nitrogen content also decreased, which were 0.033mg/L, 0.026mg/L, 0.010mg/L and 0.014mg/L, respectively. The level of eutrophication was medium,indicating that planting water spinach can decrease the content of ammonia nitrogen and nitrite nitrogen.Planting water spinach can improve water quality. FC1 group(10% spinach coverage) ensured a proportionate growth of rice,crayfish and finless eel with lower cost, In FC1 group, the production reached 318.2kg each mu of rice, 128.2kg each mu of finless eel, 55.1kg each mu of crayfish 21.4kg each mu of water spinach, 13970.7yuan each mu of output value, 6073.6yuan each mu of profit.4. Effects of Bacillus subtilis on water quality and benefit of rice-crayfish-finless eel mode;We raised finless eel(1200 individual each mu) and crayfish(3000individual each mu)in the circular furrow of rice field. Bacillus subtilis was added in the circular furrow biweekly, according to the concentration of 100 g each mu. The results indicated that compared with BTW group(without Bacillus subtilis), the dissolved oxygen of water in TW group(with Bacillus subtilis preparation)increased significantly from 3.62mg/L to 5.80mg/L. The ammonia nitrogen content decreased from 0.669mg/L to 0.478mg/L, and the nitritenitrogen content also decreased obviously, and the level of eutrophication was medium. The results showed that adding Bacillus subtilis could obviously increase the dissolved oxygen, and decreased the content of ammonia nitrogen and nitrite nitrogen.Adding Bacillus subtilis could improved water quality and got the best economic benefit among four test group. The production effect reached 314.0kg each mu of rice, 139.6kg each mu of finless eel, 58.1kg each mu of crayfish 20.3kg each mu of water spinach, 14910.5 yuan each mu of output value, 6713.4yuan each mu of profit.5. Preliminary study on Ecological breeding of finless eel;In 2013, after dissecting the finless eel, we found that there were more pregnant female ones(67.5%) weighed 1.2-1.9liang among finless eel, which were suitable as female parents. When finless eel weighed3.6liang or more, the proportion of male finless eel was high(87%),which were suitable as male parents.According to this result we chose appropriate finless eel as parents, raised them in reticulated boxes(40mesh)and pond with water spinach, separately, with a(1:1) ratio of male and female. Later,we saw about 7 cm long finless eel in the root of water spinach, it indicates the root of water spinach is the suitable place for eel breeding. At the same time, the number of eel larval in the pond were more than that in the net cage significantly. This may be related to a lot of eel larval leaking from the mesh.In 2014, experiment was set in reticulated boxes with 60 mesh.We used six different ratio of male and female finless eel.Under the same total number of finless eel, the ratio of male to female ratio was different(6:6,8:4,9:3) and under the same ratio, numbers of male and female were different(3:3,4:4,5:5). The results showed that the number of finless eel larval was the most with a(3:3) ratio of male and female raised in reticulated boxes.6. Acute toxicity of four common non-pyrethroid pesticides in finless eelThis study was carried out to evaluate the acute toxicity of four common non-pyrethroid pesticides, Glyphosate ammonium salt,Isoprocarb-chlorpyrifos, Jinggangmycin enzyme and Avermectin, in finless eel larval, and to provide science basis for using pesticides without accident in rice planting. Finless eel was exposed to four pesticide solution. The LC50 after 96 h of Glyphosate ammonium salt,Isoprocarb and chlorpyrifos, Jinggangmycin enzyme and Avermectin were 4239.24ul/L, 55.34ul/L, 2.82ul/L and 0.35ul/L, respectively,which were different significantly.The acute toxicity of Avermectin was higher than other three pesticides, while Glyphosate ammonium salt was the lowest.According to this result we could estimate the safe concentrations of four pesticides: Glyphosate ammonium salt 423.9ul/L, Isoprocarb chlorpyrifos 5.534ul/L, Jinggangmycin 0.282ul/L, Avermectin 0.35ul/L.So,it should be avoided using pesticides during raising finless eel. |
PDF Full Text Request