Development of an environment-friendly feeding management for pond-reared fish species in the Segara Anakan Lagoon, Java, Indonesia

Inefficient feeding practices for producing fish in captivity create environmental problems. Therefore, the feed input should be reduced to a level that does not result in negative impacts of fish production. Reducing feed input can be done by periodic feed deprivation which does not necessarily decrease the fish production. This study was designed to investigate the effect of repeated unfed–fed cycles on the growth and feed utilization of the orange-spotted grouper Epinephelus coioides raised in floating net cages in estuarine ponds. The trial was conducted in the north east of Segara Anakan, Java, Indonesia. The fish were purchased from local fishermen and mean fish body weight was 53.2 g. After acclimation in the cages for 2 weeks, 500 fish were randomly assigned to four feeding groups. The groups included: fish fed daily as a control (C); fish not fed every Monday and Thursday and fed on Tuesday and Wednesday, then on Friday, Saturday and Sunday (T1); fish unfed every Sunday, Monday and Thursday and fed on Tuesday and Wednesday, then on Friday and Saturday (T2). The experiment ran for 10 weeks. The results showed that reducing feed input by repeating unfed–fed cycles induced compensatory growth of the fish. Application of this feeding regime provides flexibility in feeding management and may reduce organic discharge into the environment. Reduction of organic pollution should help the sustainable use and conservation of the Segara Anakan ecosystem.     

Degradation profile of azoxystrobin in Andisol soil: laboratory incubation

The fate of azoxystrobin in soil under the effect of different temperature is of interest because application directions specify soil-surface treatments for number of agricultural pests. Temperature is an important factor governing the rate of degradation in soil pore. The purpose of this investigation was to understand better the effect of temperature on the degradation of azoxystrobin in Japanese Andisol soil. This was done through laboratory incubation of soil at three different temperatures (5 °C, 20 °C, 35 °C). First-order kinetics could be used to describe degradation of azoxystrobin under controlled condition of temperature (r² ? 94). The results showed that, during the 120-day incubation period for azoxystrobin, 64%, 70%, and 78% of applied azoxystrobin were degraded at 5 °C, 20 °C, and 35 °C, respectively. By using the Arrhenius equation, the activation energy of degradation of azoxystrobin fungicide was calculated (7.48 ± 1.74 kJ mol^?1) in soils, which confirm that temperature had a significant influence on the degradation rate. Q₁₀ value of 1.11, for azoxystrobin, indicated that the response of fungicide dissipation to temperature was large. For azoxystrobin, there was a much larger difference in dissipation rates at 5 °C and 35 °C, indicating that biological and/or chemical degradation of azoxystrobin may have nearly reached its optimum at 35 °C.