http://hdl.handle.net/10862/819 Mon, 06 Apr 2026 11:10:49 GMT 2026-04-06T11:10:49Z https://repository.seafdec.org.ph:443/bitstream/id/18e90a3b-410e-435b-8049-1152eb611061/ http://hdl.handle.net/10862/819 http://hdl.handle.net/10862/469 A modelling of eutrophication in Laguna de Bay as a tool for rational resources management Mitsumoto, Ikuro.; Santiago, Alejandro E. A lake model originally developed for Shin-Nippon Meteorological and Oceanographical Consultants Co., Ltd (METOCEAN) was used with modification to simulate the water quality of Laguna de Bay. The METOCEAN model made use of the 1984 meteorological and water quality data collected from different local government agencies. Hydraulic modeling was applied to obtain basic circulation patterns which the water quality modeling was based upon. Results of the hydraulic modeling suggests that steady backflow of saltwater from Pasig River reaches deep inside the bottom layer of the lake although the lake water flows out through the Pasig River. Thus, the water quality model for Laguna de Bay focused on the unique role of the salt water intrusion in limiting phytoplankton productivity. The effect of saltwater intrusion was simplified as the change of depth of euphotic zone in the lake water estimated from the Secchi disc transparency. For simplicity and expandability of the model as a predicting tool, Secchi disc transparency was the only forcing function considered in the study. Modelling resolution of water quality has 4 boxes horizontally and 3 levels vertically. Calibration of the water quality model was carried out by running the model repeatedly until satisfactory agreement with measured data was obtained under average wind condition (Eastern wind, 1.5 m/sec.) Other wind directions including no wind condition were also tested to see the effect of wind on water quality. Validation of the water quality model was done for 1985 to 1988 as continuing simulation from the calibration in 1984 under the average wind condition. Then simulation of the condition of the lake from 1991 to 1995 based on the 1984 data used in the calibration was tried changing only the Secchi disc transparency data. Initial results of the water quality model differentiated conditions with and without saltwater intrusion. Without saltwater backflow, higher concentration of total inorganic nitrogen and inorganic phosphorus and low dissolved oxygen especially in the bottom layer are predicted. Under this condition, release of large amounts of nutrients in the sediments is expected to be dominant source of total inorganic nitrogen in the lake. The study is the first attempt to model the lake. The model still needs calibration and validation with measured values of recent years before adapting its usefulness as a tool for predicting water quality of Laguna de Bay. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/10862/469 2001-01-01T00:00:00Z http://hdl.handle.net/10862/824 Parasitic crustaceans in fishes from some Philippine Lakes Lopez, Nellie C. Parasitic crustaceans are among the most harmful parasites of fishes. Certain species cause disease outbreaks and mortalities in aquaculture, facilities, and sometimes in natural systems, resulting in serious economic losses. Edible fishes from some Philippine lakes also show infestation by parasitic crustaceans. The branchiuran, Argulus indicus Weber, and the copepod, Lernaea cyprinacea Linnaeus, were recovered from the skin and base of the dorsal fin, respectively, of the mudfish Channa striata from Laguna de Bay. L. cyprinacea was also found on the white goby Glossogobius giurus in Naujan Lake. In La Mesa Reservoir, the gills of wild populations of tilapias Oreochromis niloticus and Tilapia zillii, white goby, and silvery theraponid Therapon plumbeus were infected with the copepod, Ergasilus philippinensis Velasquez. An isopod, Alitropus typus Edwards, was recovered from the buccal and gill cavities of several fishes from Lake Taal, namely; the mud gudgeon Ophiocara aporos, cardinal fish Apogon thermalis, silvery theraponid, and cage cultured Oreochromis niloticus. Previous reports and above finding indicate wide host specificity of the parasites. Of these four parasites, only Ergasilus philippinensis has not been reported to cause mass mortality in cultured fishes. Measures should be undertaken to prevent their introduction to other water bodies in which they do not yet occur. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/10862/824 2001-01-01T00:00:00Z http://hdl.handle.net/10862/840 Biological monitoring in west bay, Laguna Lake: Phytoplankton composition and water pollution Francisco, Jose C.; Perez, Teresita R. Phytoplankton composition and density were studied in three (3) stations in West Bay, Laguna Lake. Blue-green algae and diatoms were the most abundant in terms of cell density. Green algae had the most number of species. Diatoms predominated in the early parts of the year, under intense light conditions. Pulses of green algae were evident toward the end of the year, under high nitrogen concentrations. BIP (Biological Index of Pollution) values were very much affected by seasonal variations in the phytoplankton community. Abstract only. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/10862/840 2001-01-01T00:00:00Z http://hdl.handle.net/10862/830 Assessment of local government's implementation of open access policy in Taal Lake, Philippines: Effects on lake conservation and management Mercene-Mutia, Ma. Theresa The effects of local government's implementation of the current national policy on open access in municipal fisheries are assessed in terms of their impact on the fishery resources of Taal Lake. Local officials and fisherfolk were interviewed and their responses were analyzed for trends in perceptions on how local open access policies affect fishing practices and productivity in the lake. A policy matrix containing certain areas of concern of local governments related to sound decisionmaking on lake fishery was designed. The study shows that local government implementation of open access policy in Taal Lake tends to have negative effects on the lake's fisheries. Open access allows for the unregulated entry of fishing practices like fish cage culture which tend to increase the pollution load in the lake. Pollution due to fish farming in cages seems to even exceed loads from domestic wastes and agricultural runoff. While fish cages flourished in the lake, the income of small fisher folk has declined because of dwindling catch from capture fisheries. It is recommended that national government agencies (e.g., Department of Agriculture, Bureau of Fisheries and Aquatic Resources, Department of Environment and Natural Resources) should forge an agreement with local government units for a continuing assessment of the fishery resources in Taal. This needs to be coupled with technical assistance to undertake sustained efforts to improve the conservation, productivity and management of the lake's aquatic resources. There is also a need to increase the budgetary allocations for new research and extension activities to address problems and issues of the fishery sector in the lake and for upgrading the capability of local and sectoral policy and decision makers on the lake's fisheries. Mon, 01 Jan 2001 00:00:00 GMT http://hdl.handle.net/10862/830 2001-01-01T00:00:00Z