The project was judged to have made considerable progress towards its stated objectives of helping farmers manage their production and minimise disease risks.
The research team implemented disease control programs during a single grow-out period on two Penaeus monodon farms - one in central Java, Indonesia and the other in northern New South Wales, Australia. These programs integrated broadly targeted disease control measures, based on established principles and designed to reduce losses caused by diseases in general. As well, the team implemented measures specifically aimed to reduce losses from the major diseases associated with the farm's geographic area.
General disease control measures implemented on study ponds on farms in both countries comprised daily examination of ponds for evidence of diseased shrimp and daily water quality assessments, also weekly macroscopic examination of 100 shrimp from each pond together with assessments of growth rates, feed consumption and survival rates. The scientists introduced specific control measures directed at white spot syndrome (WSS) during two grow-out periods on the Indonesian farm, and during one grow-out period at the Australian farm monitored bluegreen algal concentrations weekly in ponds.
The Indonesian farm comprised five ponds; two were stocked intensively (40/m2) and two semi-intensively (15/m2). A semi-closed water exchange system was adopted and all water was treated with 30 ppm 60% calcium hypochlorite for three days prior to use in ponds. Postlarvae were exposed to 100 ppm formalin for 30-40 min prior to stocking and then they were tested by PCR assay to ensure they were negative for WSS virus. Ponds were fenced to exclude WSS virus carriers.
In the first trial, no significant disease outbreaks occurred in these ponds during the four-month grow-out period. Survival rates were respectively estimated at 70 and 80% for the intensive and semi-intensive ponds. The remaining (control) pond on the study farm, as well as most ponds stocked on other farms in the locality, experienced severe losses due to WSS during the study period.
In the second trial, prawns grew normally until 2.5 months, by which time they had reached 13-15 g in weight. Following a period of heavy rain, floodwater from surrounding areas, carrying wild and farmed prawns (presumably infected with WSSV) entered the reservoir and grow-out ponds. Subsequently, the farm's main generator failed, leaving the ponds without aeration for two days. There followed an outbreak of WSS in all ponds. Emergency harvesting (which would have yielded a still-profitable 2 tonnes of prawns from trial ponds) had to be delayed for one week due to temporary lack of cold storage facilities. Consequently, only one tonne of prawns was harvested from the four ponds.
The Australian farm comprised 25 intensively stocked (50/m2) ponds. The team implemented the program on 10 'study' ponds, while a reactive diagnostic and advisory service only was provided for the remaining 'control' ponds. Although bluegreen algal blooms (>100 cells/ml Oscillatoria sp.) occurred in six study ponds during the grow-out period, the scientists detected no effects on shrimp health. However, outbreaks of a previously undescribed disease, designated 'monodon ganglioneuritis' (MGN), caused losses in both study and control ponds. These losses were minimised by harvesting ponds as soon as economically feasible after MGN outbreaks began.