Browsing by Subject "Ecological balance"
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Book chapter- In SS De Silva (Ed.), Tropical Mariculture, 1998 - Academic PressThis chapter focuses on the historical and current practices of milkfish farming in the Philippines. The Philippines ranks among the top 12 largest fish producers in the world and the milkfish, Chanos chanos, is the official national fish. The milkfish production in the Philippines has fluctuated sharply, but on average, has relatively stagnated over the past decade, partly due to the shrimp boom and low price of milkfish. The milkfish industry has been responsible for the significant loss of valuable mangrove swamps and forests. The loss of mangrove means loss of habitats and biodiversity including nursery grounds for feeding and refuge of commercial fishes, shrimps, crabs and mollusks. Milkfish ponds in the Philippines are either privately owned or leased from the government. Brackish water fish ponds are valuable real estate and good management adds to their value. For milkfish farming, stocking rate should be based on the pond environment and carrying capacity, and the fish size at stocking and the market size desired.
Will microbial manipulation sustain the ecological balance in shrimp (Penaeus monodon) hatcheries? - In TW Flegel (Ed.), Advances in Shrimp Biotechnology : Proceedings to the special session on shrimp biotechnology, 5th Asian Fisheries Forum, 11-14 November 1998, Chiengmai, Thailand, 1998 - National Center for Genetic Engineering and BiotechnologyA shift in preferred methods employed to contain bacterial diseases in the hatchery phase of shrimp culture has resulted largely from the unsuccessful control by and deleterious effects of chemotherapy. Manipulation of hatchery microbial ecology has gained popularity, but for successful implementation, this niche-filling approach requires a thorough understanding of the epidemiology of bacterial diseases in the hatchery. This study examined the responses of Vibrio harveyi populations, (associated with luminescent vibriosis in shrimp larvae) to various physico-chemical factors and various hatchery components. Results showed that V. harveyi had a wider range of tolerance to environmental parameters than larvae of Penaeus monodon, such that control measures based on manipulation of these parameters might not be feasible. However, it was evident from the results that there were components in the shrimp hatchery environment that could be manipulated to control high populations of V. harveyi. The natural microflora of seawater, as well as the microbial flora associated with the diatoms Skeletonema costatum and Chaetoceros calcitrans negatively affected the survival of V. harveyi in experimental mixed cultures. The successful manipulation of such benign microbial components to compete with and exclude potential pathogens is necessary to sustain ecological balance in the shrimp hatchery environment.