Rebalancing 127 can separate complex problemsinto severallevels and factors, and compare and find the weights for different solutions, and provide the basis for the optimum solution AHP first classifies the problem into different levels based on the nature and the purpose of the problem, constructing a multilevel structure model ranked as the lowest level (program for decision making, measures etc ) compared with the highest level(the highest purpose). Based on AHP, we can establish the stratification diagram shown in Figure 3 Competitive relationship teen the decision Excreta quality adapt to the degree Oxygen s crustacea fish Figure 3. AHP stratification diagram. At last, we make consistency check of the result, finding that the consis- tency ratio of each expert's judgment matrix is below 1, so the consistency of the judgment matrix is acceptable. Finally we figure out the weight of the numbers of all the species in Population 2, as shown in Table 1 Table 1 Weight of each species in Population 2 as measured by AHP. Herbivorous fish Crustaceans Echinoderms Here we adopt population competition model to confirm the weight of es in Population 2: N1=N1(e1+nN2), N2=N2(e2+mM),Rebalancing 127 can separate complex problems into several levels and factors, and compare and find the weights for different solutions, and provide the basis for the optimum solution. AHP first classifies the problem into different levels based on the nature and the purpose of the problem, constructing a multilevel structure model ranked as the lowest level (program for decision making, measures etc.), compared with the highest level (the highest purpose). Based on AHF, we can establish the stratification diagram shown in Figure 3. ................ .Competitive relationship .. . . . . . . . . . . .. . between the decision .. . . . . . . . . . . . . . Food requirements . Environment to . . . of the algae Excxeta quality, • adapt to the degree . . . . ............... .......... T O Figure 3. AHP stratification diagram. At last, we make consistency check of the result, finding that the consis￾tency ratio of each expert's judgment matrix is below 1, so the consistency of the judgment matrix is acceptable. Finally we figure out the weight of the numbers of all the species in Population 2, as shown in Table 1: Table 1. Weight of each species in Population 2 as measured by AH-RP Species Weight Herbivorous fish .21 Crustaceans .23 Molluscs .31 Echinodermis .24 Here we adopt population competition model to confirm the weight of each species in Population 2: N1 = Ni(e1 +y71N2), N2. N2.(e2 + 'yNi)