Now showing items 7-26 of 27

    • Conference paper

      An ecological assessment of seven major lakes in the Philippines 

      MT Zafaralla - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      An ecological assessment was done on the seven major lakes in the Philippines, namely; Laguna de Bay, Taal, Naujan, Lanao, Mainit, Buluan, and Bato. The assessment was based largely on secondary data and some primary data. The ecological parameters considered for each lake were focused on published information as well as those unpublished but were made accessible to the author by researchers and agencies of government. The different lakes are classified into three ecological categories, namely; critically degraded, degraded, threatened, and underdeveloped. Where adequate data on a lake is available, emphasis is also given on the examination of the nature of land use, lake development measures, climatic variations in terms of rainfall, and ecological conditions in the lake as they affect fish production. Finally, lake specific and general recommendations are forwarded for management purposes.
    • Conference paper

      An environmental assessment of the aquaculture potential of Lake Gawaan, Lake Lenneng and Lake Banao/Danum at the Mt. Province 

      RG Dang-awan, M Estima, P Gayagay, A Pagtan & MAA Ramos - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      This study reviews the existing conditions of the three Mt. Province lakes: Lake Gawaan, Lake Lenneng and Lake Banao/Danum. Three mechanisms were employed. First is the overview of the resource capabilities. This includes the geographical, physical and biological characteristics, as well as the identification of nearby communities and the possible market distribution channels. The physical characteristics are the watershed type, color of water, kind of shoreline, source of water, water fluctuation levels and transparency/turbidity. Biological and chemical characteristics comprise the primary productivity, dissolved oxygen, nitrate, pH, ammonia, and stock availability (catch composition, gear type, seasonal distribution and production rate). The second mechanism is the understanding of the limitations of the area and development prospects which could cater to the needs of the growing population. This tackles suitable aquaculture practices that may be adopted at the areas concerned in order to increase fish production at the Mt. Province. The last mechanism is to determine if the combined efforts of the non-government organizations, government agencies and other concerned groups could be improved to prevent a piece-rate resource development program. Results showed that favorable conditions for fish culture are present in the three lakes. Culture of fish in net cages and pens appears suitable for the lakes.
    • Conference paper

      Fish culture in cages in Lake Danao, Cebu 

      SN Tanduyan & PC Bontia - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Lake Danao is a picturesque inland body of water having an area of 685 ha located in the municipality of San Francisco in Pacijan Island, Camotes, Cebu. At the middle of the lake is a circular islet with an area of one acre. This lake is a potential area for cultivation of fishes in pens and cages. To date there are only two agencies which use the lake for fish production, namely; the Department of Agriculture Regional Office No 7 Carmen-Lake Danao Fishery Complex Research Outreach Station and the CSCST-Fishery and Industrial College, San Francisco, Cebu. The following are the ranges of selected water quality parameters: salinity, 0-0.5 ppt; water temperature, 27-29 °C; pH, 8.5-9. The lake has no definite inlet and outlet of water and is free from pollutants. The water is clear with assorted vegetation. The soil is coarse, silty and sandy. The present study has shown the feasibility of growing tilapia in cages in Lake Danao.
    • Conference paper

      Fish in a man-made lake: what is there to eat? (Ecological studies in La Mesa Reservoir) 

      RA Abesamis, AC Mamaril & NC Lopez - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Since 1975, a number of ecological studies have been done in La Mesa Reservoir (also known as La Mesa Dam or La Mesa Lake). Eight species of fish are known to occur in the lake; of these species, one is stocked to control the proliferation of algae. The plankton community of the reservoir has been found to be remarkably diverse, with at least 62 species of zooplankton and possibly 70 species of phytoplankton. The high biological diversity is due to this lake being a protected area as it is Metro Manila's main source of drinking water. A confluence of several factors that preserve this condition of high aquatic biodiversity is possible: (1) Little perturbation in its water quality and its watershed occurs. (2) During high water levels, numerous coves and embayments and the moderate depths create a myriad of ecological niches and refuges for the aquatic biota. (3) Plankton diversity is likely enhanced by abundance of edible algal species (for herbivorous zooplankton) and only occasional moderate algal blooms. (4) Low fish predation tolerates large-sized species in the plankton, i.e., Filipinodiaptomus insulanus, a copepod endemic to only a few large areas in Luzon. (5) Nuisance algae are controlled by stocking of tilapia fry and the occasional use of algicide (CuSO4).
    • Conference paper

      A freshwater red alga Compsopogon coeruleus (Balbis) Montagne from Bucal, Calamba, Laguna, Philippines 

      L Intong & MR Martinez-Goss - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Compsopogon coeruleus (Balbis) Montagne was observed for the first time along the shallow, flowing portions of the spring that occurs naturally in Bucal, Calamba, Laguna. A year-round study of some habitat conditions in the sampling site was done. These conditions included air and water temperature (mean=28.5°C), pH (mean=6.5), orthophosphate (mean=0.26 ppm), ammonia-nitrogen (mean =0.52 ppm), depth of water (mean=12 cm), speed of current (mean=0.19 m/s) and light intensity (mean=770 foot candles). This alga seems to be a good indicator of organic pollution.

      A description of morpho-cytological characteristics in situ and in culture is given. Better growth was observed in a defined inorganic medium using different mixing waters (distilled, tap and filtered Bucal waters) over plain mixing waters. Germination of presumptive cortical cells into uniseriate filaments and monospore germination was observed after about 10 days of incubation in all media.
    • Conference paper

      Impact assessment of cage culture in Lake Taal, Philippines 

      MM Alcañices, RC Pagulayan & AC Mamaril - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      The environmental impact of cage culture on water quality of Lake Taal was assessed from March 1996 through February 1997. Three stations were considered namely: Balas, which serves as station 1 (non-cage area) and Sampaloc and Laurel, stations 2 and 3 (cage areas), respectively. Monthly water samples with two replicates were collected using a van Dorn sampler at 0, 5, 10 and 15-m depths in all stations. Below surface water from the inside of the cages was also collected. Water temperature, water transparency, pH, and conductivity were determined in situ. Dissolved oxygen, chloride, NO3, NH3, PO4, and total P were analyzed in the laboratory. Phytoplankton density and algal biomass (through cholorophyll a) and primary productivity indices were determined with the light-and-dark bottle method.

      Of the water quality parameters, conductivity and DO had significant differences between non-cage and cage areas. Conductivity gave significant difference (P<0.01) between control and cage area during the wet season. Highest conductivity value (2100 µ S/cm) was observed in station 3. Mean values of DO gave significant differences (P<0.05) in the different stations throughout the study period. A decrease of DO to 2.5 mg/1 was observed below 10-m depth around the cage areas. Analysis indicates that cage culture leads to oxygen depletion in the water column. The presence of cage structures decreased the flow rate resulting to weak circulation. The reduced water circulation in effect decreased the supply of oxygen and removal of toxic waste metabolites from the vicinity of the fish farm, and reduced the supply of plankton. These results suggest that the impact of cage culture in Lake Taal is minor but can alter the lake ecosystem if not properly managed. Zoning and continuous water quality monitoring are needed.
    • Conference paper

      Lake Lanao: Its past and present status 

      RP Rosagaron - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Geographically located in Central Mindanao, Lake Lanao is the second largest lake in the Philippines. The lake is famous locally for its various uses and internationally for its endemic cyprinids. This paper intends to inform the local leaders and the national planners about Lake Lanao's dwindling fisheries resources, the extinction of some endemic cyprinids, and the current interventions as well as suggested action plans to increase fish production and to conserve the remaining species in the lake. The past and present studies on the lake are also reviewed. Early and latest statistics on the lake's fisheries production are presented to invite the interest of all sectors in coming up with the integrated approach to protect, conserve and increase its fisheries production. Local and national interventions to conserve and increase fisheries production are discussed. These include the setting up of BFAR Fisheries Station in Kialdan, Marantao; the establishment of a fish hatchery in Poona, Marantao by Southern Philippines Development Authority; the formation of Save Lake Lanao Movement by the local leaders; the creation of Lake Lanao Research and Development Council; the current concern of Philippine Council for Aquatic and Marine Research and Development-DOST; and the extension and research and development thrusts of the Mindanao State University, College of Fisheries in Marawi City.
    • Conference paper

      Managing 'sinirapan' Mistichthys luzonensis Smith in Lake Buhi, Camarines Sur: Insights from its biology and population dynamics 

      VS Soliman & MFHA Sergio - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      The population dynamics and related aspects of the biology of 'sinarapan' Mistichthys luzonensis Smith, the world's smallest commercial fish, are used as basis in formulating management strategies for this goby in Lake Buhi, Camarines Sur. Mesh size limit (4.1mm) and catch limit, estimated through length-based analytic fishery methods, are proposed. Yield-per-recruit analysis using length-frequency data for 11 months provided the quantitative indices used in estimating fishing limits. Closed season for 'sinarapan' was established from temporal pattern of recruitment and the reproductive biology of the species. Much of the data on 'sinarapan' came from studies in Lake Manapao. To improve the recruitment success of 'sinarapan', a habitat enhancement scheme in Lake Buhi is hereby recommended.
    • Conference paper

      Mechanisms for lake formation in the Philippine archipelago 

      RS Punongbayan & EL Listanco - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Topographic depressions, which when filled with water become lakes, can originate in a number of ways as a result of volcanic processes and activities, crustal and fault movements, stream processes, dissolution of rocks, downslope or mass movements, shoreline processes, glaciation, acolian processes, organic or animal activity and meteorite impacts. Man has also made both intentionally and unintentionally artificial depressions and dams that give rise to man-made lakes. But the mechanisms of formation of most Philippine lakes remain unknown although those of some are well established. Examples are cited in this paper. Lakes with similar mechanisms of formation may possess similar geomorphological, geological, and physico-chemical characteristics.

      Directions for Philippine lacustrine research should cover issues on 1) the still unknown origin of most Philippine lakes, 2) assessment of lake-related hazards and risk mitigation in order to reduce disasters, 3) history of climate change as recorded in lacustrine sediments, and 4) policies and strategies for better utilization and development of lake resources which must recognize the truth that lakes are but ephemeral features of the landscape and do not last forever.
    • Conference paper

      A modelling of eutrophication in Laguna de Bay as a tool for rational resources management 

      I Mitsumoto & AE Santiago - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      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.
    • Conference paper

      Parasitic crustaceans in fishes from some Philippine Lakes 

      NC Lopez - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      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.
    • Conference paper

      Pasig River backflow and its effect on the water quality of Laguna de Bay, Philippines 

      AC Gonzal, CB Santiago & WB Afuang - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      The backflow of Pasig River into Laguna de Bay was closely monitored beginning April 28, 1997 based on the expected high tide in Manila Bay and the average low lake level of 2.5 m in Station W (N 14°27.7'; E 121°08.5') located at the west lobe of the lake. Saltwater intrusion was first detected during of the highest high tide (i.e., 1.5 m at 1430 h) on April 29. Water from Pasig River flowing into the lake was black and had a characteristic odor of hydrogen sulfide. With the light house (or 'Parola') at the mouth of Pasig River as the reference point, movement of saltwater in the lake was monitored and the area affected estimated with the use of GPS 38 Personal Navigator®. Up to mid May (Week 2), the movement of saltwater into Laguna de Bay was hampered by the intermittent calm weather conditions and moderately strong northeasterly wind ('hanging amihan'). When the wind direction shifted and the southwesterly wind ('hanging habagat') became strong on Week 3 (May 18 to 20), strong water movement and fast diffusion of saltwater into the other parts of the west lobe of the lake were observed. During this period of rapid change in the lake (May 21-24), a high frequency monitoring was conducted in Station W. Fluctuations in chloride ion concentration, conductivity and total dissolved solids, Secchi disc reading, turbidity, dissolved oxygen, and other parameters were noted in the station. Heavy rainfall in the area on May 24-26 and run-offs from the watershed and overflow from the river tributaries increased the lake level. The elevation of the water level resulted in draining out of the lake water into Pasig River to Manila Bay and this practically ended the year's saltwater intrusion into Laguna de Bay. Movement of saltwater reached almost the whole area of the west and central lobes of the lake on the first week of June (week 5) as evidenced by the clearing of water in those areas. It was estimated that clearing of the entire lake because of saltwater movement takes about 2-3 months.
    • Conference paper

      Preliminary observations on the diel feeding patterns of Nile tilapia Oreochromis niloticus (L.) in Laguna de Bay, Philippines, with the aid of the computer model MAXIMS 

      H Richter, U Focken, K Becker, CB Santiago & WB Afuang - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Nile Tilapia, Oreochromis niloticus, cultured in cages in Laguna de Bay, were sampled on two occasions in 1995, each time over a 24-hour cycle. The weights of stomach content were averaged and analysed with the computer model MAXIMS. The model predicted that, in May, larger fish feeding on natural food alone fed continuously from dawn to dusk, ingesting 4.9 to 5.4% of their body weight (wet weight basis) whereas smaller fish had two feeding periods per day, from sunrise to mid-morning and again from mid-afternoon until after sunset, ingesting between 13.0 and 13.7%. In August, fish were given supplemental feed that ran out around mid-day, after which they continued to ingest natural food. The fish ingested 3.8 to 4.0% supplemental feed and 4.4 to 4.7% natural food per day. In May, most of the stomach contents consisted of the blue-green alga Anabaena spiroides, whereas in August, the natural food was made up principally of detritus. On the basis of these findings, it is recommended that supplemental feed be given in several doses spread throughout the day.
    • Conference paper

      SEAFDEC contribution to the ecological awareness of Philippine Lakes 

      RR Platon - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Since 1976 the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD), through its Binangonan Freshwater Station has been continuously involved in research on various aspects of inland waters, with emphasis on Laguna de Bay. Lakes Paoay, Taal, Sampaloc and Naujan have also been studied to a limited extent. Research efforts focused on monitoring activities of various biological and physico-chemical parameters in the lake; pollution studies; improvement of practices towards an environmentally sound and sustainable aquaculture enterprise; socio-economic impacts of aquaculture on lakeshore communities and other related activities. The Department has been actively collaborating with various national and international agencies as well as non-government organizations in its effort, to improve its research capabilities. The research results have been published in both local and international scientific journals and proceedings.
    • Conference paper

      Some limnological features of the northern shore areas of Volcano Island, Lake Taal 

      NC Lopez, SN Javier & AC Mamaril - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Physico-chemical and biological features of the northern shore areas of Volcano Island, Lake Taal observed at monthly intervals from four stations during the period 1994 and 1996 indicate varied microhabitats inhabited by a variety of plants and animals. Physico-chemical characteristics of surface waters were: temperature, 28-35°C; dissolved oxygen content, 3.5-6.2 ppm; pH, 7.5-8.9; salinity, 0-24 ppt; and conductivity, 1.6-4.3 S cm-1. Substratum types were mainly sandy with pebbles or rocks or sandy-muddy. Characteristic submerged plants were the eelgrass Vallisneria gigantea and filamentous green algae. In the eelgrass region, atyid shrimps, mostly Ciridina gracilirostris, commonly occur. Snails such as Melanoides costellaris and Terebia granifera were the most abundant benthic animals collected. Other invertebrates identified from core samples were Corbicula manilensis, annelids, crustaceans and chironomid larvae.
    • Conference paper

      Species and proximate composition of Laguna de Bay phytoplankton cultured in three different nitrogen-phosphorus ratios and their utilization by Nile tilapia 

      ML Cuvin-Aralar, U Focken, K Becker & CB Santiago - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Natural phytoplankton populations from Laguna de Bay were used in outdoor batch culture experiment in 1-ton capacity circular concrete tanks and 60-liter glass aquaria for a maximum duration of 72 days. The treatments consisted of the following nitrogen-phosphorus ratios: 2N: 1P, 6N: 1P, and 12N: 1P. The growth and species composition of phytoplankton were monitored in each of the three treatments. The phytoplankton were partially harvested at weekly intervals. The proximate composition of the freeze-dried harvest was also analyzed. The freeze-dried harvest was also used to feed Nile tilapia Oreochromis niloticus (L.) to determine effects of the different N-P ratios on the utilization of phytoplankton by fish. The fish were fed isonitrogenously and ration ranged from maintenance requirement for the first week to 3 times maintenance requirement for the succeeding weeks. Results showed that green algae, particularly the Chlorococcales group, dominated all the cultures. This was followed by diatoms. The blue-green algae consisted the third group in all treatments. Gross energy, crude protein, crude fat, neutral detergent fiber and crude ash content of the phytoplankton harvest did not vary significantly among treatments. However, crude protein expressed as percentage of organic matter was significantly higher in the treatment using 12N: 1P compared to those cultured in lower N-P ratios. Nile tilapia fed phytoplankton from 12N: 1P and 6N: 1P ratios showed significantly better growth than those fed with phytoplankton cultured in the lowest N-P ratio.
    • Conference paper

      The status of tilapia aquaculture in Lake Sebu, South Cotabato 

      ZM Beniga - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      Tilapia culture in Lake Sebu started in the early 1970's and is now considered the backbone of the economy and major driving force of the development of the Municipality of Lake Sebu. About 19% of Lake Sebu's 354 ha water area is used for aquaculture. The present tilapia production system is not as intensive as in other lakes in the country. The daily 3-ton tilapia harvest is marketed in the different towns within the province and in neighboring provinces. Municipal Ordinance 01, Series of 1994 regulates fish cage establishment within the lake. The local government unit launched a semi-annual 'Oplan Linis', a clean up operation to remove floating debris, water hyacinth, and other vegetation along the lakeshore. Reforestation has been implemented as part of the watershed management program. For centralized marketing and effective collection of revenues, a fish port was opened in January 1997. The tilapia industry in Lake Sebu is now confronted with several setbacks. Poor-quality seeds require a longer culture period and, despite higher inputs, still result in low production. Fish kills, locally termed 'kamahong', are becoming more frequent and devastating. Market competition is another problem. Producers of intensively fed tilapia from Lake Sebu have to contend with a large volume of unfed and low priced tilapia from Lake Buluan (Lutayan area).
    • Conference paper

      Stock assessment of commercially important fishes in Naujan Lake 

      RA Pasumbal & CT Perez - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      The study aimed to assess the capture fisheries of Naujan Lake with emphasis on commercially important fish species and to determine the extent of their exploitation.

      Four major fish landing centers in the municipalities of Socorro, Pola, Victoria and Naujan were surveyed from May 1995 to December 1996. Eight types of fishing gear had been recorded. The most commonly used was gill net or 'pante', followed by fish pot 'bubo', fish corral 'baklad', spear 'salapang', spear gun 'pana', fish trap 'patanga', encircling net 'takilis' and long line 'kitay'.

      Tilapia comprised 61% of the total fish production of the lake, followed by therapon (16%), goby (4%) and mudfish (2%). The other species caught were 'pla salid', catfish, mullet, carp, milkfish and shrimp, which contributed 17% to the total production. Migratory fishes like the mullet and milkfish, on the other hand, showed a declining trend in production.
    • Conference paper

      Sustainable development of Philippine lake resources: An agenda for research and development 

      RDI Guerrero - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      There are 59-70 lakes in the Philippines. With the exception of Laguna de Bay and Lake Taal, little is known about Philippine lakes although they contribute as much as 15% to the total annual fisheries production of the country. There is need for an integrated basin approach for the sustainable management of Philippine lake resources. Among the research strategies recommended for sustainable management of Philippine lakes are: (1) studies on lake fisheries resources - fish stock assessment, effects of fishing and other human activities on lake productivity, the biology of major aquatic species, and the carrying capacity of lakes; and (2) lake management studies - the rational use of lakes, strengthening management, enforcement and institutional mechanisms, and socio-economics focused on the users of lakes.
    • Conference paper

      Translocation of the clupeid Sardinella tawilis to another lake in the Philippines: A proposal and ecological considerations 

      AC Mamaril - In Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculture: Proceedings … Seminar-Workshop held on October 21-23, 1997, INNOTECH, Commonwealth Ave., Diliman, Quezon City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources
      The dwindling commercial catch of Sardinella tawilis (Clupeidae), locally known as 'tawilis', reported in recent years by local fisher folk in Lake Taal, Batangas, Philippines, could be a result of the interaction of factors such as over fishing, destructive fish-capture techniques, changes in water quality, and others. Like the rest of the handful of endemic freshwater fish species in the Philippines, S. tawilis is threatened with depletion of its stocks, if not with extinction in the near future. A conservation strategy that could be considered is the translocation of 'tawilis' to another lake in the Philippines, whose ecological features closely resemble those of Lake Taal and where 'tawilis' would receive socio-economic and cultural acceptability. Cases of clupeid introductions - natural and man-made, successes and failures - are presented from published literature. Special attention is given to the case of a well-planned trans-country (Thailand-to-Indonesia) attempt to introduce a clupeid fish. The broader questions of biodiversity, endemicity, conservation, and fish community structure in Lake Taal (and elsewhere) must be underpinned by sound basic taxonomy and ecology.