148 The UMAP Journal 30.2(2009) (milkfish)and feeding them specially formulated fishmeal creates the larger amounts of fish necessary to meet growing demand. Doing so also doesn't require the sustenance of a variety of different creatures. Why is it not possible simply to apply modernagriculture methods to aquaculture? Why shouldnt Filipinos continue to increase the yield of milkfish with specially- designed fishmeal, just as a farmer in America s Midwest increases the yield of a soybean or corn harvest by using specially-formulated seed and fertilizer? Initial observations may lead to the conclusion that such an approach is both viable and desirable. After all, why not simply remove the excess fish waste and sell it as fertilizer for local farmers? That might be possible. However, just as land farmers eventually realized that growing certain crops year afteryear leads to decreased yields because of nutrient depletion in the soil, fish farmers encounter the threat of decreased over because growing only milkfish depletes water quality by causing algae and waste to grow uncontrollably. The excess algae reduce coral growth in the same way that lack of crop rotation depletes the soil of nitrogen. Both conditions appear to offer better results in the short term but destroy the longer-term viability of the system. Still, for people to change behavioral practices, it is important to demonstrate the limiting effects of the current system. For our model, this requires showing that farming only milkfish causes water quality and the amount of harvestable fish to decline. To model the current system, we took our model from Task 1 and set th e values for the populations of everything but milkfish and algae to zero. population chokes off the viability of the milkfish because of the increased oxygen demanded by the algae and consequently the decreased quantity available to the fish However, it is unrealistic to assume the current system consists only of milkfish and algae. We know that the current system has a water quality of 100bacteria/ml and 15 ug/lof chlorophyll, both of which are much greater than the suggested 0.5-1.0 x10 bacteria/mI and 0. 25 pg/l of chlorophyll suggested to be acceptable for adequate coral growth Coral growth acts like a skyscraperin that it allows more fish to grow in a given space through vertical partitioning. Therefore, we gradually adjust ne populations of the various species in our model to achieve the level of a steady-state equilibrium of water quality when the ecosystem consists of only milkfish and algae, because the algae do not entirely dispose of the waste from the milkfish; without another species such as blue mussels to reduce the waste of the milkfish, the milkfish grow uncontrollably, even if the 20% that mature each year are removed by humans after reproducing If humans harvest also immature milkfish the level of milkfish will drop below sustainability. This human harvesting can reduce the level of waste in the water somewhat, although it is insufficient to achieve a steady state148 The UMAP Journal 30.2 (2009) (milkfish) and feeding them speciallyformulatedfishmeal creates the larger amounts of fish necessary to meet growing demand. Doing so also doesn't require the sustenance of a variety of different creatures. Why is it not possible simply to applymodern agriculture methods to aquaculture? Why shouldn't Filipinos continue to increase the yield of milkfish with specially￾designed fishmeal, just as a farmer in America's Midwest increases the yield of a soybean or corn harvest by using specially-formulated seed and fertilizer? Initial observations may lead to the conclusion that such an approach is both viable and desirable. After all, why not simply remove the excess fish waste and sell it as fertilizer for local farmers? That might be possible. However, just as land farmers eventually realized that growing certain crops year after year leads to decreased yields because of nutrient depletion in the soil, fish farmers encounter the threat of decreased overall yield because growing only milkfish depletes water quality by causing algae and waste to grow uncontrollably. The excess algae reduce coral growth in the same way that lack of crop rotation depletes the soil of nitrogen. Both conditions appear to offer better results in the short term but destroy the longer-term viability of the system. Still, for people to change behavioral practices, it is important to demonstrate the limiting effects of the current system. For our model, this requires showing that farming only milkfish causes water quality and the amount of harvestable fish to decline. To model the current system, we took our model from Task 1 and set the values for the populations of everything but milkfish and algae to zero. Figure 3 shows the decline in water quality over time. The rise in algae population chokes off the viability of the milkfish because of the increased oxygen demanded by the algae and consequently the decreased quantity available to the fish. However, it is unrealistic to assume the current system consists only of milkfish and algae. We know that the current system has a water quality of 1010 bacteria/ml and 15 Mg/l of chlorophyll, both of which are much greater than the suggested 0.5-1.0 x106 bacteria/ml and 0.25 Mg/1 of chlorophyll suggested to be acceptable for adequate coral growth. Coral growth acts like a skyscraper in that it allows more fish to grow in a given space through vertical partitioning. Therefore, we gradually adjust the populations of the various species in our model to achieve the level of current water pollution in Bolinao. Again, our model is unable to produce a steady-state equilibrium of water quality when the ecosystem consists of only milkfish and algae, because the algae do not entirely dispose of the waste from the milkfish; without another species such as blue mussels to reduce the waste of the milkf•sh, the milkfish grow uncontrollably, even if the 20% that mature each year are removed by humans after reproducing. If humans harvest also immature milkfish, the level of milkfish will drop below sustainability. This human harvesting can reduce the level of waste in the water somewhat, although it is insufficient to achieve a steady state