Now showing items 22-32 of 32

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      Improved production of mud crabs Scylla serrata in marine pens with used tires and bamboo tubes as shelters 

      MC Basaya - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      One serious problem in mud crab farming systems is cannibalism and low survival, but this can been offset by provision of shelters. Two types of shelters were tested on mud crabs grown in bamboo pens set in a mangrove area in Tiniguiban Cove in Puerto Princesa. Six pens, each 3 m x 3 m in area, were built side by side (the whole array 9 m x 6 m in area). Two pens were provided bamboo tubes, two had used tires, and two had both shelter types. The bamboo tubes were about 46 cm long and 13 cm in diameter, open on both ends, and each with a node retained as partition. The bamboo tubes were laid in one layer at the middle of the pens, 48 tubes in each of the two pens. The used tires were 50 cm in diameter, placed 20 cm apart in one layer in the middle of the pens, 12 tires in each of two pens. In the two pens that had both shelter types, half the number of bamboo tubes and used tires were laid out. All shelters were tied and did not move off the bottom. Juvenile crabs of 46 g body weight were stocked at 63/pen or 7/m2. The crabs were fed chopped trash fish at 5% of body weight daily at 0800 h and 1600 h. Mud crabs in the pens with bamboo tubes as shelters had the best survival (79%), weight gain (81 g), net production (4.5 kg/pen), and feed conversion ratio (4.9), as well as net income (P544,202/ha-yr) and return on investment (48%). The results clearly indicated that bamboo tubes were better shelter for juvenile mud crabs than used tires. Bamboo tubes were presumably more familiar to mud crabs reared in bamboo pens. Having node partitions in the middle, the bamboo tubes had smaller and safer hiding places. These shelters effectively reduced crowding, aggression, and cannibalism, and thus increased the survival and growth of mud crabs. The used tires evidently did not provide a good shelter configuration nor sufficient protection for mud crabs in bamboo pens.
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      Shrimp pond effluents and water quality in Imbang River, Negros Occidental 

      ET Taberna - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The contribution of shrimp farm effluents to the pollution load in Imbang River, Negros Occidental was measured during the period May 1993 to February 1995. Shrimp pond effluents were characterized and the pollution load estimated. The pond effluents had low average nitrite (0.0025 ppm) and nitrate (0.06 ppm) and optimum (for shrimp culture) pH 7.9, phosphate 0.15 ppm, dissolved oxygen 5.20 ppm, and salinity 23.3 ppt. Ammonia was 0.13 ppm on average in most farms, above the safe level for shrimp, and total suspended solids was 23 ppm, about 2.5x the allowed limit for effluents. Biochemical oxygen demand (20 ppm) and settleable solids (0.15 ppm) were still with acceptable limits. Residues of organochlorine pesticides were present at very low concentrations, well below the safe levels for aquatic life. Most of the pollution load came from the regular water exchanges over the 4-month crop cycle, at least every two weeks in low-density farms and more frequently in the high-density farms. The total draining of pond water at harvest contributed a minor load. Total solids from shrimp farms contributed a huge load, about 181,325 mt/yr. Total suspended solids contributed 1,285 mt/yr and settleable solids <1 mt/yr. The total BOD load was 154,367 kg/yr. The phosphate load was about 1,080 kg/yr, and the total nitrogen load was 1,225 kg/yr. The effects of effluent release from farms were localized. Upstream water quality and other uses of the river were not affected. Since most of the shrimp farms were located 1.5–2 km from the sea, the release of effluents during water exchange and at harvest did not adversely affect water quality downstream of these farms. Where such draining increased the levels of ammonia, phosphate, and total suspended solids in the river, the effect was significant only within 250 m from the release point, and the pollutants were dissipated about 550–800 m downstream The other water quality variables were at low levels in the pond effluents and did not affect the river water during draining. Often the concentrations of pollutants in the river were higher before than during draining of pond effluents. Stations upstream of the release sites of pond effluents often had high pollutant concentrations from other upstream sources.
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      Socioeconomic profile of tuna fishers in northwestern Luzon 

      VR Panay & NL Ledda - In TU Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      A study of tuna fishers in northwestern Luzon (Region I) was done by means of a questionnaire. The 511 respondents included 178 from Ilocos Sur, 200 from La Union, and 133 from Pangasinan. Most of them were younger than 50 years, had basic education, married with large families of 3-9 children, owned the houses they lived in, and had low annual incomes of about P35,000. Fishing was their sole means of livelihood for almost all the respondents, except some for whom farming supplemented the income from fishing. Majority worked every night or day, 36% went fishing every other night or day, and 13% went fishing five times a week. Most fishers went out to sea at night. Fully 52% of the fishers worked within 50 km from shore; 38% fished within 51–100 km, and the others went out farther than 100 km and even 200 km. La Union fishers worked closest to shore (average 38 km) and Pangasinan fishers the farthest (average 92 km). More than 90% of all fishers used motorized bancas, which made it possible for them to fish farther out to sea. Only 36% of the fishers owned the boats and fishing gears they used, and most did not. In all three provinces, the capital for the fishing enterprise came mainly from savings. The average cost of motorized boats was P31,200; non-motorized boats, P1,200. Longlining was the most preferred fishing method in the region. Hand lining was the second most preferred in Ilocos Sur and Pangasinan. Gillnetting and other methods (rabuk, kawil, pana, and bira-bira) were ranked third and fourth, and trawling was the least preferred. Drift gill nets used for tunas cost on average P680; tuna long lines, about P600; tuna hand lines, P345; and troll lines, P750. The main species caught by the fishers were skipjack tuna, yellowfin tuna, frigate tuna, Spanish mackerel, rainbow runner, dolphinfish, sailfish, blue marlin, and threadfins. In Ilocos Sur, most fishers reported catches of 11-20 kg in one trip, and a few fishers caught 50 kg. Spanish mackerel and sailfish gave the fishers better incomes than the other species. Fish catches and prices and fisher incomes in La Union were lower than in Ilocos Sur. Threadfins were more abundant in La Union. Fishers in Pangasinan did not catch sailfin, marlin, or threadfins, but caught higher volumes (20–60 kg/trip) of the other species.
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      The squid fishery in Carigara Bay, Samar: catch of Photololigo duvaucelii by squid jigs and Sepioteuthis lessoniana by hanging squid pot 

      JO Dickson & BR Ricafrente - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The squid fishery in Carigara Bay used the following gears: hanging squid pots, squid jigs, drive-in net, and spear by slingshot. Hanging squid pot operations were concentrated in the municipal waters of Capoocan and Carigara and targeted Sepioteuthis lessoniana. During the one-week survey in Carigara Bay, 705 hanging squid pots with markers were found offshore of barangays Culasian, Pinamopoan, Cabul-an and Talarian, all in Capoocan town. Other operators in Carigara, Babatngon, Barugo, and San Miguel towns hung their squid pots from fish shelters (arong) offshore of Carigara and Capoocan towns. Test fishing operations were conducted in Carigara Bay from January to December 1992 using the hanging squid pot, squid jigs, and a squid cast net. A 16 hp motorized boat F/B Ellah Meh was used during the fishing operations. A total of 162 days test fishing with 15 hanging squid pots yielded 125.7 kg of the longfin squid Sepioteuthis 1essoniana. Sixty nights of fishing with the ordinary squid jig yielded 97 kg of Indian squid Photololigo duvaucelii. Two test fishing operations with the squid cast net yielded no squid at all. The S. lessoniana (75-500 g body weight) caught by pots were larger than the P. duvaucelii (7-270 g) caught by jigs.
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      Sugar mill effluents and water quality in Imbang River and Malisbog River, Negros Occidental 

      HJ Gonzales - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The effluents of two sugar mills and the effects on water quality in the receiving rivers were studied. Sugar mill A was located in Barangay Dos Hermanas in Talisay and discharged directly into Imbang River. Sugar Mill B was located in Barangay Hawaiian in Silay City and discharged into Malisbog River, a tributary of Imbang. Both sugar mills had sedimentation tanks and lagoons for partial wastewater treatment prior to discharge. Water sampling was done at 13 stations at effluent discharge sites and also upstream and downstream of these sites. The sugar mill effluents were particularly high in biochemical oxygen demand (BOD 109–419 mg/l), total suspended solids (168–384 mg/l), and total solids (1,185–1,234 mg/l), also high in ammonia (0.2–0.5 mg/l) and water temperature (31–38°C), but low in dissolved oxygen (2–5 mg/l). Measured stream flows varied at the different stations and were generally lowest at stations near sugar mill A and at stations near sugar mill B. At these sites, the depth of Imbang River varied from about 10 cm during low water flow in December–May to about 2 m during high water flow in June–November. During normal low flows, the sugar mill effluent comprised 75–85% of the total stream volume, causing highly polluted conditions immediately below the outlets. Sugar mill A discharged high annual loads of solids, BOD, nitrate, and phosphate into Imbang River, whereas sugar mill B loaded plenty of solids, BOD, ammonia, and phosphate into Malisbog River. The sugar cane milling season in Negros Occidental started in October and ended in May, coincident with the dry season. Significantly higher levels of BOD and nutrients, but lower DO, were observed in the river during the milling season (see figures in Gonzales et al., this volume), both because of greater discharge and lower dilution by lower stream flows. River water quality was better at the stations upstream than downstream of the sugar mills. Stations near the sugar mills had BOD, ammonia, and solids at concentrations exceeding the allowable limits set for river water by the Department of Environment and Natural Resources.
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      Transplantation, hatchery, and grow-out of window-pane oyster Placuna placenta in Guimaras and Iloilo 

      SS Garibay, SN Golez & AS Unggui - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The windowpane oyster Placuna placenta (local name kapis) used to be harvested in large quantities and support a shellcraft industry in the Philippines, particularly in Panay Island. But the fishery and the industry declined markedly by the 1990s. Studies were conducted to transplant kapis and also to develop hatchery techniques for it in an effort to counter the population depletion. Kapis with average shell heights of 7 cm and 10 cm were transplanted from Roxas City in northern Panay Island and from Oton, Iloilo in southern Panay to Taklong Island in Guimaras during the rainy season (July–November) and the dry season (February–June). Survival of the transplants was higher during the dry season (57–60%) than during the rains (35–48%). Sexually mature kapis 10 cm in shell height were induced to spawn by temperature manipulation, water level manipulation, and use of ultravioletirradiated sea water. Spawning was successfully induced by raising the water temperature to 29±0.5oC. Eggs measured 45 μm on average, and fecundity was 5,000–10,000 per female. Kapis larvae were reared on a combination of the microalgae Isochrysis galbana, Tetraselmis sp., and Chaetoceros calcitrans, maintained at a density of 100,000 cells/ml. Three water treatment schemes were tested for larval rearing: chlorination, ultraviolet irradiation, and filtration (control). Larvae survived to the umbo veliger stage (180 μm, day 10) in chlorinated sea water whereas mass mortality occurred at the straight-hinge stage (days 4–) in both UV-treated and filtered sea water.
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      Treatment of shrimp pond effluents by sedimentation and by seaweed and mussel biofiltration 

      NR Fortes & VL Corre Jr. - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Tiger shrimp Penaeus monodon were stocked in three 1,000 m2 ponds at 12,000 juveniles/pond and grown for 141 days. Water quality in the ponds was monitored over the grow-out period, particularly before and after every water change. BOD, chlorophyll a, and total dissolved solids of the effluent increased over the grow-out period due to increased biomass and feed input. Similar trends were observed for inorganic nitrogen, reactive phosphorus, total suspended solids, and hydrogen sulfide. Concentrations decreased after draining and reflooding. Soil samples also showed increases in organic matter available phosphate, carbon, and nitrogen content over the grow-out period.

      Effluents from semi-intensive shrimp ponds were discharged into eight treatment ponds (each 200 m2): three sedimentation ponds, three with Gracilaria stocked at 20 kg/pond, and two with mussels stocked at 10/m2. Measurements were made of pH, ammonia, nitrite, nitrate, reactive phosphorus, biochemical oxygen demand, chlorophyll a, total suspended solids, and total dissolved solids in the water in the treatment ponds after effluent addition, one week and two weeks later, and before draining. Soil pH, organic matter, and phosphorus were also analyzed every two weeks. The changes in these variables were similar among the three treatments in the eight ponds. In this study, water quality of effluents improved after one week in the treatment ponds.
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      The tuna fishery off northwestern Luzon: catch of purse seines and hand lines operating around fish-aggregating 'payaw' 

      VV Prado - In TU Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The tuna fishery along northwestern Luzon was studied from March 1994 to April 1995. About 120 units of fish aggregating ‘payaw’ were set 20–100 km offshore and fished by about 350 handline boats and 6 purse seines. The handline landing areas were in Apatot, San Esteban, Ilocos Sur and in Darigayos Cove, La Union. The resident purse seine was based at Poro Point in San Fernando, La Union; the others were occasional operators. Skipjack tuna Katsuwonus pelamis was the primary species landed by the purse seine and yellowfin tuna Thunnus albacares was mostly landed by the hand lines. These species occurred year-round with peaks during the dry season. The purse seine was operated about 9 sets per month, and landed an average of 51 mt fish monthly (catch rate 5.7 mt/set), highest in November, December and March. Handline fishing was carried out an average of 17 days a month (catch rate about 19 kg/boat-day). The tuna fishery was adversely affected by strong monsoon winds and typhoons. The rough seas inhibit fishing and give the tuna populations much needed respite from the intense fishing pressure.
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      Use of soybean meal and rice bran in formulated diets for the grouper Epinephelus coioides 

      ET Marasigan, SL Miag-ao & AE Serrano - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Two diets were formulated to include 8–14% soybean meal and 9–18% rice bran, 34–40% fish meal, 4–5% mussel meal, and 7–8% Acetes shrimp meal, and 11–13% cod liver oil. Soy bean meal and rice bran were included at 4:1 ratio together to replace 12.5% and 25% of the animal protein sources in the two diets. The two diets were prepared in dry D form and moist M form. The four test diets, D12.5, M12.5, D25, and M25 diets had 40–42% protein and 4,000 kcal/g gross energy. The control diet used was a dry diet with 44% crude protein and 4,260 kcal/g, made with 30% Peruvian fish meal, 8% squid meal, 22% Acetes shrimp meal, 8% cod liver oil, 8% soybean oil, but no plant protein sources. The five diets were fed to juvenile grouper (mean weights ranging from 1.63 ± 0.47 to 2.41 ± 0.91 g) in indoor 400 L concrete tanks (10 fish per tank). After 10 weeks, growth, feed intake, feed conversion ratios (1.2–2.2), and survival (60–80%) of juvenile grouper were not significantly different between the test diets and the control. The carcass composition of the harvested grouper was not significantly different among diets. Protein utilization was best among the fish fed the test diet D12.5. This study showed that soybean meal and rice bran at 4:1 ratio can be included in formulated diets for grouper to replace 12.5% to 25% of the animal protein sources. However, the results for the test diets may also have been due to other factors - the high fish meal content, inclusion of mussel meal, and increase in cod liver oil.
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      Water quality in Imbang river, Negros Occidental: effluents and pollutant loads from agriculture, sugar mills, households, and shrimp farms 

      GA Gonzales, HJ Gonzales, RC Sanares & ET Taberna - In TU Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      An ecological assessment of Imbang River in Negros Occidental was undertaken from December 1992 to February 1995. The effluents from sugar mills, households, shrimp farms, sugarcane plantations and rice fields were characterized and their pollutant loads estimated. Water quality and invertebrate assemblages were analyzed at several sites along the river to determine the environmental status. Results showed significant seasonal and site variations in water quality along Imbang River. The dry season, coinciding with the milling season, was the more critical time of the year as water quality tended to deteriorate. The segments of the river near the sugar mills and households had the poorest water quality. Sugar mill effluents had high water temperature (average 33oC but as high as 50oC), low dissolved oxygen, high total solids, the highest settleable solids (average 2.5 and as high as 17 m/l), and the highest biochemical oxygen demand (average 259 ppm but as high as 14,800 ppm BOD). Domestic effluents had low pH, high ammonia, very high BOD, plus detergents or surfactants and high levels of fecal coliform bacteria. Agricultural runoff had high nitrate, high total solids, and the highest total suspended solids (average 296 ppm but as high as 5,095 ppm TSS). Shrimp ponds used saline water of average 23 ppt, and had the highest total solids (average 23,456 ppm and as high as 57,400 ppm). By far the major contributor of pollutant loads into Imbang River was agriculture, due to its huge areal extent and huge volume of water use and run-off. Agricultural run-off carried the highest annual loads of 7,858 kg phosphate; 6,495 kg ammonia; 794 kg nitrite; 67,212 kg nitrate; 16,987 metric tons settleable solids; 16,800,000 mt total solids, and 11,890,000 mt total suspended solids; but only 297 mt BOD. Sugar mill effluents had the highest BOD load (1,583 mt/yr) and also had high nutrient loads. Household effluents contributed the second largest loads of solids next to agriculture, and also added surfactants (966 kg/yr) and fecal coliforms into the river. The six shrimp farms at the lower reaches of Imbang River were a minor contributor of pollutants into the river, annually adding about 891 kg ammonia; 1,077 kg phosphate; and 181,325 mt total solids.
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      Yield and agar quality of three red seaweed Gracilaria species grown in tanks at three salinities 

      MSR Ferrer & AN Marasigan - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Gracilaria changii, G. firma and G. tenuistipitata were collected from the eastern coast of Sorsogon in southeastern Philippines and grown in concrete tanks at the SEAFDEC Aquaculture Department in Iloilo in May-June and in September-October 1994 at a stocking density of 1 kg/m2 and at three salinities (15, 25, and 35 ppt). In the first run, the highest specific growth rates per day were 2.5% at 25 ppt for G. changii, 3.6% at 35 ppt for G. firma, and 3.2% at 15 ppt for G. tenuistipitata. In the second run, the highest daily growth rates were 1.4% for G. changii, 1.2% for G. firma, and 3.3% for G. tenuistipitata, all at 15 ppt. Nutrient and light limitation in the second run led to lower and even negative growth rates. Gracilaria changii and G. firma were euryhaline but grew best at 25–35 ppt; G.tenuistipitata was not euryhaline and grew best at 15 ppt. The highest growth rates in tanks were at salinities close to those in the natural habitat: G. changii at 25 ppt, G. firma at 35 ppt, and G. tenuistipitata at 15 ppt. The estimated potential production (dry weight kg/m2-yr) in tanks was 1.65 kg G. changii at 25 ppt, 2.49 kg G. firma at 35 ppt, and 2.35 kg G. tenuistipitata at 15 ppt.

      Agar yields from three Gracilaria species varied from 5% to 23%, on average lowest in G. tenuistipitatata, and were generally higher at 25 ppt and 35 ppt than at 15 ppt. Agar gel strengths were also strongly affected by salinity and were highest at 35 ppt. Gracilaria tenuistipitata had very high gel strength (average 782 g/cm2 but as high as 1,082 g/cm2 comparable to agarose), well above the specified 750 g/cm2 for the international market. Gracilaria changii and G. firma had average gel strengths of 516 and 558 g/cm2, well within the range (400–600 g/cm2) for commercial agar used in the food industry. The sulfate contents were lower at 15 ppt and were even 0% in several instances, especially in G. tenuistipitata. The gelling temperature of 32°C and melting temperature of 97.3°C qualifies G. tenuistipitata for the international market. Gracilaria changii and G. firma had melting temperatures of 93–95°C but gelling temperatures of just 29°C. Farming techniques for these seaweeds should be developed to produce enough raw material for profitable commercial processing.