Effects of Fish Culture on Water Quality of an Integrated Mariculture Pond System.
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Six mariculture ponds were flooded with seawater since 1996. During this time the ponds were stocked with finfish (milkfish and rabbitfish), which were fed on locally produced fish feed. Some water quality parameters such as temperature, salinity and oxygen saturation were measured twice a day for three years (1998-2000), while nutrient concentrations were measured weekly for one year. Both nutrient concentration and oxygen saturation levels have shown a trend indicating eutrophication. Oxygen concentration changed from an average of 7.16 mg/l in October 1998 to 2.2 mg/l in March 2000 with a negative linear regression of 0.69 during the morning hours. From August 1998 to April 1999 dissolved inorganic ammonia concentration increased by 9 µg-at NIl, from 8.91 to 18.02 with a positive linear regression of 0.79. During this period soluble reactive phosphorus increased by 3.55 µg-at PII from 4.36 to 7.91 with a positive linear regression of 0.75. In this paper the rate of eutrophication and the limit at which the ponds have to be dried/limed before restocking are discussed.