Now showing items 1-4 of 4

    • Conference paper

      The ecological impact of tilapia cage culture in Sampaloc Lake, Philippines 

      AE Santiago - In LM Chou, AD Munro, TJ Lam, TW Chen, LKK Cheong, JK Ding, KK Hooi, HW Khoo, VPE Phang, KF Shim & CH Tan (Eds.), The Third Asian Fisheries Forum. Proceedings of the Third Asian Fisheries Forum, 26-30 October 1992, Singapore, 1994 - Asian Fisheries Society
      Sampaloc lake showed imminent biological death as a consequence of intensive tilapia farming in floating net cages. The progressive disappearance of dissolved oxygen in the entire water column may be an irreversible trend due to continuous feeding. The high amount of BOD5 and the near toxic concentration of total ammonia and total sulphides are ominous signs. Other ecological changes in the lake are the non-appearance of Microcystis bloom, change in phytoplankton composition, number, and species diversity.
    • Conference paper

      Incidence and causes of mass fish kill in a shallow tropical eutrophic lake (Laguna de Bay, Philippines) 

      ML Cuvin-Aralar, AE Santiago, AC Gonzal, CB Santiago, MR Romana-Eguia, SF Baldia & F Palisoc Jr. - In 9th International Conference on the Conservation and Management of Lakes. Conference proceedings, 2001 - Shiga Prefectural Government
      Mass fish kills in Laguna de Bay, the largest lake in the Philippines, has been reported as early as in the 1930’s. With the introduction of and development of aquaculture in this lake, considerable attention and concern was focused on the problem. Records of mass fish kill in the lake mainly from unpublished sources and reports from fisherfolk were reviewed and the causes categorized. The data covered the period 1972 to 1998. Among the commercially important fish species affected were milkfish (Chanos chanos), Nile tilapia (Oreochromis niloticus), bighead carp (Aristichthys nobilis), snakehead (Channa striata), catfish (Clarias macrocephalus and C. batrachus, Arius manilensis), silver perch (Terapon plumbeus) and goby (Glossogobius giurus). The first three species are widely used in aquaculture and the rest are important in open water fishery. Sixty percent of mass fish kill incidents were due to low dissolved oxygen with more than half of these cases associated with blue-green phytoplankton blooms. Fish kills due to pollution from agriculture and industries, fish pathogens and other causes are also discussed. The incidence of mass fish kill reached its peak between 1977 to 1986. Records show that the most number of fish kills (80%) occurred between the months of May to September. The lakeshore towns in the central arm of the lake had the highest incidence of fish kill reported with 46% and followed by the west arm of the lake with 38% of all fish kills recorded.
    • Article

      Tilapia cage culture and the dissolved oxygen trends in Sampaloc Lake, the Philippines 

      AE Santiago & RP Arcilla - Environmental Monitoring and Assessment, 1993 - Springer Verlag
      The 28-hectare tilapia cage culture that occupied the 104-hectare Sampaloc Lake, a crater lake, shifted to intensive method in 1986 when tilapia growth slowed done at the beginning of 1982. Thus, commercial feeds became the main source of allochthonous organic matter in the lake. Total feeds given annually for the 28-hectare cage culture at 3 croppings per year amounted to 5250 tons. At feed conversion ratio of 1 : 2 a significant portion of the feeds given ended as organic wastes in the lake. In 1988, tilapia cage operators began experiencing their worst occurrences of fishkill, worth millions of pesos. An assessment of the dissolved oxygen condition of Sampaloc lake in late 1989, 1990 and mid-1991 showed ominous trends which might adversely affect the use of Sampaloc lake for fishery.
    • Article

      Turbidity and seawater intrusion in Laguna de Bay 

      AE Santiago - Environmental Monitoring and Assessment, 1991 - Springer Verlag
      The ecological role of seawater intrusion in Laguna de Bay is assessed due to the operation of the Napindan Hydraulic Control Structure (NHCS). Turbidity is recognized as one limiting factor in the lake's biological productivity. Hence, to stop the natural backflow of seawater to Laguna de Bay removes one important contributory factor in facilitating an early water clearing of Laguna de Bay for a higher annual biological productivity.