132 The UMAP Journal 30.2 (2009) The land area of the Philippines is 300, 000 km, the sea area is 27. 6 mi2. The Philippines is surrounded by the sea, and has lots of islands; the depth of the sea between islands is mostly within 50 m. Based on the sea area, we calculate the sediment per square meter to be 0. 12-0.33 g/m2. Since the sediment is usually not very thick, we assume that the depthis 0.1m, so that the sedimenter cubicmeteris 1.2-3.3 g/m Then based on the information given in the problem, we get the results of Table 4 Table 4 Element Concentration(g/L) c(10%) 117333 N(04% 4y-133 P06%) From the table, we can see eutrophication is very serious, and the coral cannot grow. The water quality is very poor, which almost matches environment in the pens Task 2b: Simulating Comparison of the current Situation ctually in the pen, there are more than just milkfish and algae. So here we have to introduce the removed species as the middle strata, and according to the requirements of the problem, adjust the numbers of the species in the middle strata to simulate the water quality in the Bolinao area until the water quality matches the one currently observed The concrete practices are as follows: Simulate the water quality (in Site D, for example) and solve the problem according to themodelin Task1 It is easier to find out the water quality from the initial values of algae, milkfish, and other species than vice versa We adopt brute-force random search Set the initial values of algae, other species, and milkfish to 100 x103, 10×103,and13×10 According to the introductory ratio between the milkfish and the algae, and the requirements for the capacity of the pen obtained from Task 2a, we introduce the algae and the milkfish respectively as 72 x 10 and 1.3 x 103, and at the same time have the introductory numbers of other species come from arandom distribution between 8 10 and 10 x 103 with the aim of searching for the theoretical value matching the observed water quality.132 The UMAP journal 30.2(2009) Further, we get the weight and number of the milkfish respectively as 172 x 106 kg and 25-34 x 106. The land area of the Philippines is 300,000 km2, the sea area is 27.6 mi 2. The Philippines is surrounded by the sea, and has lots of islands; the depth of the sea between islands is mostly within 50 m. Based on the sea area, we calculate the sediment per square meter to be 0.12-0.33 g/m2 . Since the sediment is usually not very thick, we assume that the depthis 0.1 mn, so thatthe sedimentper cubic meter is 1.2-3.3 g/rmn. Then based on the information given in the problem, we get the results of Table 4. Table 4. Element concentrations. Element Concentration (pg/L) C (10%) 117-333 N (0.4%) 47-133 P (0.6%) 70-200 From the table, we can see eutrophication is very serious, and the coral cannot grow. The water quality is very poor, which almost matches the environment in the pens. Task 2b: Simulating Comparison of the Current Situation In Task 2a, we discussed the independent farming of the milkfish; but actually in the pen, there are more than just milkfish and algae. So here we have to introduce the removed species as the middle strata, and according to the requirements of the problem, adjust the numbers of the species in the middle strata to simulate the water quality in the Bolinao area until the water quality matches the one currently observed. The concrete practices are as follows: Simulate the water quality (in Site D, for example) and solve the problem according to the model in Task 1. It is easier to find out the water quality from the initial values of algae, milkfish, and other species than vice versa. We adopt brute-force random search: "* Set the initial values of algae, other species, and milkfish to 100 x 101, 10 X 10 3 , and 1.3 x 10 3 . "* According to the introductory ratio between the milkfish and the algae, and the requirements for the capacity of the pen obtained from Task 2a, we introduce the algae and the milkfish respectively as 72 x 103 and 1.3 x 10', and at the same time have the introductory numbers of other species come from a random distribution between 8 x 101 and 10 x 103, with the aim of searching for the theoretical value matching the observed water quality