Studies On The Optimization And Energy Balance Of Ecolgical System Of Intensive Grass Carp Ponds

Ctenopharyngodon idellus is a very popular fish in freshwater aquaculture of China, its annual output is the highest of all freshwater fishes and accounts for nearly one quarter of total output, so it takes an important part in national economy. Grass carp has lots of characteristics such as strong adaptability, wide range of feed sources, rapid growth and delicious meat, and it can be cultured all over China. But there are some disadvantages in traditional cultivation like low feed utilization rate, large-scale outbreak of fish diseases, water pollution caused by the abuse of fishery drugs and so on. These problems have caused bad influence on aquaculture environment and food safety.The problems exposed by traditional cultivation call us to find new way. Intensive cultivation uses advanced management, creates optimum growth environment for high-density fish, accelerates grow speed and increases fish production to get high productivity and efficiency. Intensive cultivation is a high yield and short breeding cycle culture method.In this study, we used land-based enclosures to study economic, ecological and social benefits and energy utilization and conversion efficiency of different ecosystems, in which Ctenopharyngodon idellus,Hypophythalmichthys molitrix, Cyprinus carpio and Litopenaeus vannamei were cultured in different mono- and poly-culture treatments. The main results were as follow:1. An Experiment Study on Grass Carp Ponds Polyculture with Silver Carp and Common CarpThe outputs,total cost vs gross receipt and synthetic efficiency index of different ecosystems, in which Ctenopharyngodon idellus,Hypophythalmichthys molitrix,Cyprinus carpio and Litopenaeus vannamei were cultured in different mono- and poly-culture treatments, were studied in land-based enclosures. There were seven treatments: grass carp treatment (G); grass carp and silver carp treatment (GS); grass carp and common carp treatment (GC) and four treatments stocked grass carp,silver carp and common carp with different proportion (GSC1, GSC2,GSC3,GSC4) .The results indicated that the water quality objectives of polyculture was better than monoculture of grass carp group; the content of Chl-a of G and GC treatments were higher than other groups. The survival rate of grass carp ranged from 93.06% to 99.18%, and the net output ranged from 1871.4 to 4765.6 kg·ha^-1;The survival rate of silver carp ranged from 90.80% to 98.49%,and the net output ranged from 1312.5 to 3034.9 kg·ha^-1;The survival rate of common carp ranged from 98.55% to 100%,and the net output ranged from 593.3 to 2264.6 kg·ha^-1. The feed coefficient ranged from 1.31 to 1.82; Total relative utilization rates of N and P ranged from 1.94 to 6.97, and the G treatment was the lowest while the GSC2 was the highest; total cost vs gross receipt ranged from 1:1.14 to 1:1.54, and GSC2 was the highest while the GSC3 was the lowest; synthetic efficiency index ranged from 0.71 to 1.33, polyculture systems were higher than monoculture significantly. The results showed that the GSC2 treatment was the best and the GSC4 treatment was the next.2. An Experiment Study on the Energy Budget and Conversion Efficiency of Ecological structure in Ployculture of Ctenopharyngodon idellusThe energy budget and conversion efficiency of different ecosystems, in which Ctenopharyngodon idellus,Hypophythalmichthys molitrix and Cyprinus carpio were cultured in different mono- and poly-culture treatments, were studied with land-based enclosures. The results indicated that the solar radiation energy during the experiment was 4970 MJ·m^-2. The solar energy utilization rates of phytoplankton ranged from 0.25% to 0.33%, the difference among each treatments was insignificant (P>0.05). The photosynthetic energy efficiency of mono-culture closure was the lowest, and significantly different from GS,GSC2,GSC3 and GSC4 treatments (P<0.05). Compare with mono-culture enclosures, the total energy conversion efficiency of poly-culture enclosures increased 43.51%,11.62%,30.16%,64.30%,38.49% and 61.90% , respectively. The GSC2 treatment was the highest, and the GSC4 was the second. The feeding energy consumption per unit of net yield of mono-culture treatment was the highest, and significantly higher than GS,GSC2 and GSC4 treatments (P<0.05). The sediment energy, which was significantly different from each treatment, ranged from 3.42 MJ·m^-2 to 17.73 MJ·m^-2 . The sediment energy of each treatment accounted for total input energy were 30.92%,12.18%,39.08%,29.43%,28.90%,28.87% and 29.80% , respectively. We could come to the conclusion that GSC2 and GSC4 treatments had high energy usage and conversion efficiency, and these two treatments were better than other treatments.3. An Experiment Study on Grass Carp Ponds Polyculture with Silver Carp,Common Carp and vannameiThe outputs,total cost vs gross receipt and synthetic efficiency index of different ecosystems, in which Ctenopharyngodon idellus,Hypophythalmichthys molitrix,Cyprinus carpio and Litopenaeus vannamei were cultured in different mono- and poly-culture treatments, were studied in land-based enclosures. There were six treatments: grass carp treatment (G); grass carp and silver carp treatment (GS); two treatments stocked grass carp,silver carp and common carp with different proportion (GSC1, GSC2); two treatments stocked grass carp, silver carp and vannamei with different proportion (GSL1, GSL2). The results indicated that the net output of grass carp ranged from 3738.09 to 6548.3 kg·ha^-1, the net output of silver carp ranged from 1097.28 to 3391.84 kg·ha^-1; the net output of common carp ranged from 1975.51 to 2828.57 kg·ha^-1; the net output of shrimp ranged from 718.80 to 958.10 kg·ha^-1; the total outputs of ecosystem ranged from 7704.8 to 11492.5 kg·ha^-1. The results of single factor analysis of variance and Duncan multiple comparison analysis showed that the difference among each treatment was significant (P<0.05). The feed coefficient ranged from 1.00 to 1.38, GSC1 treatment was the lowest and GSL2 treatment was the highest; Total relative utilization rates of N and P ranged from 2.01 to 7.37; total cost vs gross receipt ranged from 1:1.41 to 1:2.12; synthetic efficiency index ranged from 0.59 to 1.39. The results of above three indicators, which were significantly different from each treatment (P<0.05), were the same: GSL2 treatment was the highest and G treatment was the lowest. The conclusion should be made that GSL2 was the best treatment of all.4. An Experiment Study on the Energy Budget and Conversion Efficiency of Ecological structure in Ployculture of grass carp ponds with fish and shrimpThe energy budget and conversion efficiency of different ecosystems, in which Ctenopharyngodon idellus,Hypophythalmichthys molitrix,Cyprinus carpio and Litopenaeus vannamei were cultured in different mono- and poly-culture treatments, were studied with land-based enclosures. There were six treatments: grass carp treatment (G); grass carp and silver carp treatment (GS); two treatments stocked grass carp,silver carp and common carp with different proportion (GSC1, GSC2); two treatments stocked grass carp, silver carp and vannamei with different proportion (GSL1, GSL2). The results indicated that the solar radiation energy during the experiment was 6658.78 MJ·m^-2. The Primary productivity ranged from 13.54 to 23.44 MJ·m^-2 and the solar energy utilization rates of phytoplankton ranged from 0.25% to 0.33%, the G treatment was the highest while the GS treatment was the lowest, the difference between each treatment was significant (P<0.05). The total inputs of each treatment ranged from 37.66 to 49.33 MJ·m^-2 and the total outputs ranged from 16.34 to 24.12 MJ·m^-2; the sediment energy ranged from 6.96¹2.39 MJ·m^-2 ; the order of total energy conversion efficiency was G<GSL1<GSC1<GS<GSL2<GSC2; the order of total energy consumption per unit of net yield was GSC2<GSL2<GS<GSC1<GSL1<G; the difference between each treatment was significant (P<0.05). The results showed that GSC2 treatment was higher than any other treatments.Two years'outdoor study fully demonstrated that no matter from economy,ecological and social benefits or from energy conversion efficiency perspective, polyculture ecosystem was better than monoculture ecosystem significantly. Here came to two good treatments and the density of grass carp: silver carp: common carp were 91.25: 18.75:46.25g·m^-2 and 62.08:51.98:44.37g·m^-2;the density of another good treatment with shrimp was grass carp: 69.39g·m^-2; silver carp: 56.46g·m^-2; vannamei: 14.80 g·m^-2 .