128 The UMAP Journal 30.2(2009) where Ei are birthrates and yi are coefficients of species interaction. According to these equations, we find that the ratio between different pecies is almost consistent with that obtained by ahP, which also confirms he correctness of our method, l In this way, we find that herbivorous fish, crustaceans, molluscs, and echinoderms can coexist and also compete. So the number of each species can be figured out based on the data in the steady state from the previous models, as shown in Table 2 Table 2. Number per pen of each species in steady state. Organism 69027 Herbivorous fish 5,638 Molluscs 8483 Echinoderms 6589 Milkfish Now we use the model to check the water quality, and make clear whether it is suitable for the continued healthy growth of the coral. First, we calculate the current concentration of chlorophyll in a fish pen. With help of relevant references, we find the regression equation between the Imber of algae and chlorophyll: N=1.2785+07568C where the units are 104/ml for N(algae) and ug/L for C (chlorophyll).For N=6.9027(from Table 2), we getC=7.43, a concentration of chlorophyll that is far beyond 0.25 Pg/L, the highest suitable concentration for the growth of coral From the available data in the problem, we figure out the mass of organic particles in the fish pen, and then work out the mass of each elemer The dry weight of echinoderms in the pen is 45.5 kg, the dry weight of milkfish excrement is 0.4-0.9 kg, so the total dry weight of excrement in the pen is 1.0-1.4 kg · The pen is10m×10mx8m, for a volume of800m3=800×103L Based on the percentage of elementorganic particles is 1186-1738 ug/L. Finally, we get the concentration of venin the problem, we figure out thenconcentrationof carbon C(10%),nitrogen(0.4%), andph bosphorus P(0.6%)(Table 3) DITOR'S NOTE: The authors paper does not give further details of the AHP calculationnor e population competition modeL128 The UMAP Journal 30.2 (2009) where e are birthrates and -y, are coefficients of species interaction. According to these equations, we find that the ratio between different species is almost consistent with that obtainedby AHP, which also confirms the correctness of our method.1 In this way, we find that herbivorous fish, crustaceans, molluscs, and echinoderms can coexist and also compete. So the number of each species can be figured out based on the data in the steady state from the previous models, as shown in Table 2. Table 2. Number per pen of each species in steady state. Organism Number Algae 69,027 Herbivorous fish 5,638 Crustaceans 6,305 Molluscs 8,483 Echinoderms 6,589 MNflUfsh 1,760 Now we use the model to check the water quality, and make clear whether it is suitable for the continued healthy growth of the coral. First, we calculate the current concentration of chlorophyll in a fish pen. With help of relevant references, we find the regression equation between the number of algae and chlorophyll: N = 1.2785 + 0.7568C, (1) where the units are 10'/ml for N (algae) and ptg/L for C (chlorophyll). For N = 6.9027 (from Table 2), we get C = 7.43, a concentration of chlorophyll that is far beyond 0.25 jug/L, the highest suitable concentration for the growth of coral. From the available data in the problem, we figure out the mass of organic particles in the fish pen, and then work out the mass of each element. "* The dry weight of echinoderms in the pen is 45.5 kg, the dry weight of milkfish excrement is 0.4-0.9 kg, so the total dry weight of excrement in the pen is 1.0-1.4 kg. " The pen is 10 m x 10 m x m, 8 for a volume of 800 m3 = 800 x 103 L. "* Finally, we get the concentration of organic particles is 1186-1738 /Lg/L. Based on the percentage of elements given in the problem, we figure out then concentration of carbon C (10%), nitrogen N (0.4%), and phosphorus P (0.6%) (Table 3). 1 EDITOR'S NOTE: The authors' paper does not give further details of the AHP calculation nor of the population competition model