142 The umaP Journal 30.2(2009) Combiningthe balancedecosystem withmarketpricing formulas demon strates how alternative fish-harvesting practices will lead to higherincome for the local population and provide the protein that they need. Fish is the most efficient source of animal protein for humans because it requires less feed to obtain the same amount of protein as chicken, beef, or pork. Akey limit of our models is scant data on prices and onratios of species necessary to recreate a balanced ecosystem. Still, our results demonstrate to the Bolinao people both the environmental and the economic value of °n8 om producing only mil由切 more diverse aquaculture wesuggestpolicy changes designed so thatthe people of Bolinao t have to choose between getting enough food to eat now and having a healthy environment in the future Table 1. Symbol key. bol Meaning Formula LmrstPPBSGDEP ant tiger praw current population of species x Pr-1 population of species X the previous month birth rate of species death rate of speciesx rate at which species X is eaten by a predator current population of algae SaPa-1+EaPr-1 P current population of mussels SiP-I+EiP, P current population of milkfish Pmyt Pmo Pmy current population of juvenile(young)milkfish BmPmo-1+0.066Pmy-1 Pmo cument population of breeding(old)milkfish SmPmo-1+0.066Pmy-1 current population of rabbitfisH P current population of starfish current population of giant tiger prawns StPt-1-EtPm-1 Cd evel of carbon dissolved YmPm+YPt -YPt Nd level of nitrogen dissolved YmPm+YPr -YP-YaPa level of chlorophyll Ya Cp level of particulate carbon YmPm+YP+YP-YPC Np level of particulate nitrogen YmPm+YtPt-YaPo level of bacteria created by individual species X142 The UMAP Journal 30.2 (2009) Combiningthe balanced ecosystemwithmarketpricingformulas demon￾strates how alternative fish-harvesting practices will lead to higher income for the local population and provide the protein that they need. Fish is the most efficient source of animal protein for humans because it requires less feed to obtain the same amount of protein as chicken, beef, or pork. A key limit of our models is scant data on prices and on ratios of species necessary to recreate a balanced ecosystem. Still, our results demonstrate to the Bolinao people both the environmental and the economic value of transitioning from producing only milkfish to a more diverse aquaculture. Finally, we suggestpolicy changes designedso thatthe people of Bolinao don't have to choose between getting enough food to eat now and having a healthy environment in the future. Table 1. Symbol key. Symbol Meaning Formula algae blue mussels milkfish rabbitfish starfish giant tiger prawn current population of species X population of species X the previous month birth rate of species X survivability rate of species X growth rate of species X death rate of species X rate at which species X is eatenby a predator current population of algae current population of mussels current population of milkfish current population of juvenile (young) milkfish current population of breeding (old) milkfish current population of rabbitfish current population of starfish current population of giant tiger prawns level of carbon dissolved level of nitrogen dissolved level of chlorophyll level of particulate carbon level of particulate nitrogen level of bacteria created by individual species X market price for species X G.z -- Dx SaP,,-, + EaPt,.I SIPjI- + BIP.-i P,lt + Pi. BmP . - "-i O.+066P,,y-1 SmrPino-1 ""+ 0.066Pt,,,-l SIP,-I ErPn-i StPt-i -FtP,_l YnP6 + YtPt- YIP YnPm + YrPr YIPL YaPa YaPa YMP7 + YrPr + YSPS -YIPL Y7nPm + YtPt - YaPa a 1~?r S t PX Pm Pt P. P. Pt PM PV Wa Chd Mx