Water quality fluctuations under floating net cages for fish culture in Lake Cirata and its impact on fish survival

Abstract

Vertical profiles of water quality were surveyed before and after mass mortality of fish cultured in cages in Lake Cirata, a man made lake in Indonesia. The first survey was performed 4 months before the mass mortality and the second survey was carried out 4 days after the mass mortality. In the first survey, the conditions below 8 m depth were reductive and anoxic, although at 8 and 10 m depth, the water became oxidative in spite of low oxygen concentration in the second survey. These changes were probably caused by strong mixing of surface water with deeper water. Eight months after the mass mortality, when the redox potential at 8 m became reductive again, exposure tests of fish were performed in different layers in the water column around the cage. During the exposure tests the redox potential of the water was less than -100 mV and 93% of carp died within 6 h of exposure at 8 m depth. These results indicated that the mass mortality was caused by the strong mixing of surface water with reductive water in deeper layers.

Observation of anoxic water mass in a tropical reservoir: the Cirata Reservoir in Java, Indonesia

“…It is different from the lakes and reservoirs in temperate areas. Effendie et al (2005) pointed out that the massive fish kill in the Cirata Reservoir was caused by a reductive condition derived from the deeper layer by strong vertical mixing. They observed an unstable temperature profile and a high concentration of ammonia in the surface layer 4 days after a massive fish kill in December 2000.…”

“…In this reservoir, massive fish kills have occasionally occurred in the fish culture lately (Garno 2002;Abery et al 2005;Effendie et al 2005). Garno (2002) pointed out that degradation of the water quality caused by increasing organic waste from the fish culture would generate this problem.…”

Aquaculture Water Quality Index: a low-cost index to accelerate aquaculture development in Indonesia

“…Freshwater aquaculture is a key activity in commercial fisheries in Indonesia, with the related products being an important source of protein for many people, especially those who live in urban areas (Effendie et al 2005). Food and Agriculture Organization (FAO) aquaculture statistics also confirmed that Indonesia produced a great many fish types to meet both domestic demand and export needs with the highest rank of fish types being Common carp (67.95 %), Nile tilapia (24.56 %), and Giant gourami (2.09 %), among others.…”

A review and SWOT analysis of aquaculture development in Indonesia

“…This may be due to poor water quality leading to more frequent or severe outbreaks of koi herpes virus disease (KHVD) (Abery et al 2005), as well as water quality parameters exceeding the physiological tolerances of the carp. In Cirata reservoir, West Java, there have been several reported mass fish kills due to degraded water quality (Effendie et al 2005;Phillips & De Silva 2006;Hayami et al 2008;Edwards 2010). During the last turnover of the reservoir's water in 2007, there was an 80% mortality of all species (Edwards 2010).…”

“…During the last turnover of the reservoir's water in 2007, there was an 80% mortality of all species (Edwards 2010). The Cirata fish kills appear to be caused by mixing of the lower anoxic layer waters, which begin at only 7-8 m depth (Effendie et al 2005;Phillips & De Silva 2006;Hayami et al 2008). Because of the shallow oxycline in Cirata reservoir (7-8 m depth), even moderate mixing due to wind-induced upwelling or vertical mixing can result in massive fish kills (Hayami et al 2008).…”