http://hdl.handle.net/10862/6108 2026-04-06T11:20:17Z http://hdl.handle.net/10862/6139 Revisiting the Ligawasan marshland in Mindanao: An indigenous resource management system study towards sustainability Sinolinding, Harris M.; Porciuncula, Fe L. Cuvin-Aralar, Maria Lourdes; Punongbayan, Raymundo S.; Santos-Borja, Adelina; Castillo, Lourdes V.; Manalili, Eduardo V.; Mendoza, Marlynn M. The Ligawasan Marshland covering an area of 288,000 ha is important to hundreds of thousands of Magindanawan Bangsamoro fisher-farmers whose basic means of livelihood are wild fishing and traditional rice farming. This study evaluates the indigenous resource management system and indigenous laws in fishing and rice farming and the effects to the sustainability of the marshland. Most of the fisher-farmers practiced traditional fishing and farming beliefs/rituals which promoted sustainability since giving respect to the marshland as a sacred place deters overexploitation. In terms of indigenous laws, bans on electric and chemical fishing, and fry catching are strictly enforced. A peaceful coexistence is preserved among the heads of barangays, traditional religious leaders, and the Bangsamoro mujahideen leaders to enable them to work in unity amidst some diversity. An exclusive open access and rights to control only among Magindanawan Bangsamoro is observed which show their control over accessibility and utilization of the marshland. Aquatic wildlife remains abundant in the marshland to include species of fish, crustaceans, mollusks, and other aquatic organisms with economic value. Values obtained on the physico-chemical properties [dissolved oxygen (DO) - 4.67 g/L; pH - 6.99; water turbidity - 53.30 cm; dissolved solids (DS) - 136.04 mg/L) of the marshland were within the normal range indicating that the area remains an ideal habitat for fish and other aquatic resources. The overall sustainability level (using ecological soundness, cultural acceptability, social justice, economic viability and technological appropriateness dimensions) of the marshland was rated moderate with a mean rating of 75.06. This indicates that the marshland has gained some degree of degradation due to the occurrence of natural calamities and centuries of utilization of the area by the fishers-farmers. Based on the findings, a sustainability framework is put forward to strike a balance between the socioeconomic and biophysical environment, and the indigenous resource management system and laws to enhance sustainability of the Ligawasan Marshland. 2005-01-01T00:00:00Z http://hdl.handle.net/10862/6136 Status and impacts of tilapia fish cage farming in Lake Bato: Some policy and management options for sustainable development Nieves, Plutomeo M. Cuvin-Aralar, Maria Lourdes; Punongbayan, Raymundo S.; Santos-Borja, Adelina; Castillo, Lourdes V.; Manalili, Eduardo V.; Mendoza, Marlynn M. An assessment and impact analysis of the fish cage arming in Lake Bato was conducted from October 1999 to January 2000 through a field survey and personal interviews with fish cage farmers, operators and key informants in 10 lakeside communities bordering Lake Bato. Tilapia fish cage farming was the most dominant activity undertaken in the lake owing to its economic contribution and performance. It is sad to note, however, that the management and protection of the lake has been neglected. Results showed that the lake is experiencing serious stress and degradation as a result of fish cage congestion numbering to more than 21,820 units indiscriminately installed all over the lake. The same is also the cause of conflicts (i.e., marginalized small-scale fishers, obstruction of navigational route, and proliferation of dummy fish cage operators) among lake users. As a consequence of expanded technology application, slow fish growth, algal bloom, fish kill, and the apparent shallowing of the lake have become alarming concerns among resource users. It is also worth noting that the industry s sustainability is now under serious threat if not properly planned, managed, and protected. It is therefore recommended that alternative policy and management options be institutionalized. This would include formulation of a lake-wide inter-Local Government Unit (LGU) fisheries ordinance, implementation of Lake Bato Resource Management Plan, organization of a lake-wide fish cage farmers and operators, conduct of collaborative and interdisciplinary research and development initiatives, conduct of technical and management training for Best Fish Cage Practice, and massive information-education-communication (IEC) for concerned municipalities. 2005-01-01T00:00:00Z http://hdl.handle.net/10862/6137 Aquaculture practices in Laguna de Bay, Philippines Santiago, Corazon B.; Focken, Ulfert; Gonzal, Angelito C.; Laron, Manuel A. Cuvin-Aralar, Maria Lourdes; Punongbayan, Raymundo S.; Santos-Borja, Adelina; Castillo, Lourdes V.; Manalili, Eduardo V.; Mendoza, Marlynn M. A survey was conducted to obtain information on the fish culture practices of the fish farmers in Laguna de Bay, Philippines. Fish farms vary greatly in size. Nile tilapia and bighead carp are the two fish species cultured in cages. Milkfish as well as tilapia and bighead carp are cultured in pens. The fish in cages and pens in the lake are grown in monoculture and polyculture systems. About one-half of the cage operators and two-thirds of the pen operators do not use artificial feeds in growing fish. Estimates of N load in the lake due to feeding indicated that the contribution of feeds to N in the water is low in relation to the N present in the water. The fish farmers vary in their practices in terms of stocking rate, culture period, and feeding. Production per unit area also varies. However, fish farmers have common concerns and problems. 2005-01-01T00:00:00Z http://hdl.handle.net/10862/6138 Hi-density tank culture of Nile tilapia (Oreochromis niloticus) using lake water with effluent management Eguia, Ruel V.; delos Reyes, Jr., Aurelio A. Cuvin-Aralar, Maria Lourdes; Punongbayan, Raymundo S.; Santos-Borja, Adelina; Castillo, Lourdes V.; Manalili, Eduardo V.; Mendoza, Marlynn M. Nine concrete tanks (2 x 2 x 1 m) were stocked with tilapia fingerlings (abw = 3.3±0.9 g) and three stocking rates (50 fish/m², 100/m², and 150/m²) were tried. The rearing period lasted for 120 days. Fingerlings were fed commercial diet containing approximately 27% crude protein. The amount of feed was adjusted based on monthly weight samplings. Pre-filtered lake water pumped through gravity aerators into the tanks was used throughout the culture period. Although production was intensified, water agitators and similar mechanical implements were not employed to cut production costs. Results show that tilapia stocked at 50/m³ grew significantly heavier at 109.2 ± 8.0 g. This was significantly better (P<0.05) than fish stocked at 100 and 150/m³, which had basically the same final weight of 82.4 ± 1.8 g and 83.4 ± 8.7 g, respectively. Likewise, survival or recovery at harvest was highest at 92.8% for the stocking rate of 50 fish/m³. The results suggest that stocking at lower densities would result to bigger fish but a lower total yield per tank, or higher stocking densities would mean higher yield but smaller individual fish size at harvest. The rate of water flow through at harvest time was equivalent to 0.30 L/min/kg biomass at the highest stocking density of 150/m³, 0.40 L/min/kg biomass at 100/m³, and 0.60 L/min/kg biomass at the lowest density of 50/m³. Siddiqui et al. (1991) suggested a minimum of 0.50 L/min/kg biomass flow rate for intensive culture of tilapia, but this was generally for clean culture water, not like lake water whose quality varies naturally. After determining the optimum stocking density, a second experiment using bigger fingerlings (57.5±12.6 g) was conducted for 101 days to determine the ideal water flow rate in the system. Varying flow rates (10 liters per minute (Lpm), 15 Lpm and 20 Lpm) were evaluated at a fixed stocking density of 50 fish/m³. Feed ration was 5% during the first two months, 4% on the third month, and 3% thereafter. Tilapia size at harvest increased with increasing flow rate when stocked at 50 fish/m³. From an initial stocking size of 57.5 ± 12.6 g, biggest fish harvests were obtained in tanks with a flow through rate of 20 Lpm (152.2 ± 15.1 g) after 101 days of culture. However, this was not significantly different to fish grown in tanks at 15 Lpm (139.9 ± 7.6 g). Smallest fish harvests were obtained at 10 Lpm at 111.20 ± 8.3 mm. A similar trend was observed with fish length at 157.7 ± 15.5 mm, 150.8 ± 11.0 mm, and 142.1±17.6 mm for 20 Lpm, 15 Lpm, and 10 Lpm, respectively. Feed conversion ratio (FCR) ranged from 1.7 to 2.5 in all treatments. The rate of water flow through at harvest time was equivalent to 1.2 L/min/kg biomass at 20 Lpm, 0.6 L/min/kg at 15 Lpm (sufficient for Laguna de Bay water), and 0.4 L/min/kg at 10 Lpm flowrate. Except for a slight increase in ammonia levels (maximum 1.1 mg/L total ammonia nitrogen) towards the final two weeks of the rearing period, water quality in the culture tanks was generally within tolerable levels throughout the run. Thus, the quality of water from Laguna de Bay can safely support the stocking density used in the experiment. However, if stocking density is further increased, aeration may need to be provided because very low early morning dissolved oxygen levels (DO) were observed, especially in tanks with high stocking density. The significant amount of sludge, mainly fish feces and uneaten feeds, effectively trapped and collected from the settling apparatus, clearly demonstrated the apparatus efficiency. Effluent water was practically rid of solid wastes, and gravity aeration oxygenated the water before it was discharged back to the lake. Ammonia, pH and DO levels of the effluent water were similar to those recorded from the water in the header tank. 2005-01-01T00:00:00Z