Conservation and Ecological Management of Philippine Lakes in Relation to Fisheries and Aquaculturehttp://hdl.handle.net/20.500.12066/51332024-03-28T22:24:27Z2024-03-28T22:24:27ZPasig River backflow and its effect on the water quality of Laguna de Bay, PhilippinesGonzal, Angelito C.Santiago, Corazon B.Afuang, Wally B.http://hdl.handle.net/20.500.12066/51602022-02-28T03:24:31Z2001-01-01T00:00:00ZPasig River backflow and its effect on the water quality of Laguna de Bay, Philippines
Gonzal, Angelito C.; Santiago, Corazon B.; Afuang, Wally B.
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.
Abstract only.
2001-01-01T00:00:00ZSpecies and proximate composition of Laguna de Bay phytoplankton cultured in three different nitrogen-phosphorus ratios and their utilization by Nile tilapiaCuvin-Aralar, Ma. LourdesFocken, UlfertBecker, KlausSantiago, Corazon B.http://hdl.handle.net/20.500.12066/51592023-03-23T02:25:17Z2001-01-01T00:00:00ZSpecies and proximate composition of Laguna de Bay phytoplankton cultured in three different nitrogen-phosphorus ratios and their utilization by Nile tilapia
Cuvin-Aralar, Ma. Lourdes; Focken, Ulfert; Becker, Klaus; Santiago, Corazon B.
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.
Abstract only.
2001-01-01T00:00:00ZPreliminary observations on the diel feeding patterns of Nile tilapia Oreochromis niloticus (L.) in Laguna de Bay, Philippines, with the aid of the computer model MAXIMSRichter, HartmutFocken, UlfertBecker, KlausSantiago, Corazon B.Afuang, Wally B.http://hdl.handle.net/20.500.12066/51582022-02-28T03:21:25Z2001-01-01T00:00:00ZPreliminary 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
Richter, Hartmut; Focken, Ulfert; Becker, Klaus; Santiago, Corazon B.; Afuang, Wally B.
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.
Abstract only.
2001-01-01T00:00:00ZA freshwater red alga Compsopogon coeruleus (Balbis) Montagne from Bucal, Calamba, Laguna, PhilippinesIntong, LizbethMartinez-Goss, Milagrosa R.http://hdl.handle.net/20.500.12066/51572022-02-28T03:22:03Z2001-01-01T00:00:00ZA freshwater red alga Compsopogon coeruleus (Balbis) Montagne from Bucal, Calamba, Laguna, Philippines
Intong, Lizbeth; Martinez-Goss, Milagrosa R.
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.
Abstract only.
2001-01-01T00:00:00Z