Analysis Of Changes In Water Quality Used For Supporting Fish Productivity Of Floating Cage/KJA (Keramba Jaring Apung) In Cirata Reservoir

Abstract

The existence of floating net cages/KJA (Keramba Jaring Apung) in the Cirata reservoir is one of the suppliers that stock fisheries needs in West Java by 40%. But along with this, the number of KJA is increasing and its existence has exceeded the legimate amount determined by the Decree of the Governor of West Java No. 41 of 2002 as many as 85,393 plots. The increase in the number of KJA in the Cirata reservoir has an impact on the decline in water quality and fish productivity. This study aims to determine the processes that cause the dynamics of fish productivity and changes in water quality for KJA aquaculture, building models that can be used as a means of analysis to explain the dynamics that occur, designing a sustainable KJA policy. The depiction of the situation is carried out using the system dynamics approach. System dynamics methodology is one of the policy modeling approaches, especially in terms of increasing understanding of how and why dynamic symptoms of a system occurs This model shows actual behaviour and simulation behaviour, based on historical data 2007-2017. The actual model and simulation show that the model and structure of the model are valid according to The Theil Statistical Test, while the model reference has also reflected its historical behaviour. Thus the model can be used for policy analysis. To formulate a sustainable KJA (floating net cage farming) policy, the policy analysis used is in the period of 2007-2040. The model structure in this research is made based on the relationship between KJA farming dynamics, productivity, policy, KJA waste, eutrophication cycle, O2 availability and technology. These variables cause eutrophication in the Cirata Reservoir and affect the production and productivity of fish for the long term. Based on these differences, the hypotheses have been proposed which cover farming of KJA productivity and eutrophication of reservoir waters. First, the model is used to simulate the likelihood of the increasing presence of KJA and the deteriorating water productivity and quality in the next 20 years. Then, by analyzing the possible scenario, the policy scenario is designed to overcome the problems that occur.

Characteristics and Changes in Water Quality Based on Climate and Hydrology Effects in the Cirata Reservoir

“…The water quality conditions in the dry season and rainy season showed that the floating cage aquaculture and land use of the Citarum Watershed had negative effects on the water quality of the Cirata Reservoir. The fishers using floating cages should be involved in education and training on efficient feeding methods and floating cage limitations because dense floating cages and overfeeding decrease fishery productivity [8].…”

“…The deposition of uneaten pellets disturbed aerobic and anaerobic bacteria activity, thus the incompletely degraded pellets produced NH 3 -N, which is dangerous for aquatic organisms [39]. A large number of floating cages in the Cirata Reservoir also caused oxygen depletion in the water [8], and it potentially caused fish deaths. Fish death in the Cirata Reservoir occurs at a DO level under 2 mg/L, and it also increases the NH 3 -N levels around the floating cages up to between 0.798 mg/L and 1.6 mg/L [40].…”

“…The Cirata Reservoir was built in 1988 for a 1008-megawatt (MW) hydropower plant, which supplied electricity for Java and Bali [8]. The other functions of the Cirata Reservoir Water 2023, 15, 3132 2 of 18 are serving as a source of clean water and for irrigation, flood prevention, tourism, a site for aquaculture, and a conservation site for animals and plants [7].…”

“…Previously, the number of floating cage aquacultures in 1988 in the Cirata Reservoir was only 74 cages [25], but recently, it has increased to 85,393 cages [8]. The promising economic profits encourage fishers to feed their fish excessively to accelerate growth [26].…”