Environmental characteristics and management challenges of brackishwater fish ponds in Cirebon Regency, West Java Province, Indonesia: a fine-scale GIS Approach

Abstract

This study presents a fine-scale Geographic Information System (GIS) method to explore existing environmental and farm management constraints at extensive brackish water aquaculture ponds located in Losari District, Cirebon Regency, and West Java Province. The sampling method followed a detailed survey method, employing high-resolution satellite imagery of worldview-2 and GIS. Detailed pond unit and layout canal maps were used to guide soil and water sampling, measurement of land elevation and tide observation. The result showed that the existing pond canals were not able to supply 4,800,000 m3 daily required quantity of culture water for the total 2,360 ha pond area due to high sedimentation at the mouth and along the canals. The result of spatial analysis of soil and water variables also indicated that, despite generally good soil and water quality, some existing environmental variables could potentially limit the productivity and sustainability of the existing brackishwater ponds. The soil variables such as phosphate (PO4-P) content (79.16 ± 28.34 mg / L) exceeded the optimum standard value of 35-46 mg/L, whilst total nitrogen (Total-N) content (0.07 ± 0.025 %) was lower than the optimum value of > 0.2%, for brackishwater aquaculture. Water quality variables comprising (NO2-N), total ammonia nitrogen (NH3-N) and nitrate (NO3-N) were also identified as limiting factors. Without a significant improvement in pond engineering and better understanding and management of existing environmental limiting factors, the increase in productivity and the sustainability of brackishwater fish ponds in the region seem almost impossible.