Use of neem oil (Azadirachta indica) to control caligid copepod infestation on Asian seabass (Lates calcarifer)

Asian seabass (Lates calcarifer) culture in marine cages have been developed rapidly in Malaysia. The high intensity of culture might facilitate several disease infection including caligid infestation. This study was conducted to evaluate the effect of neem oil (Azadirachta indica) against caligid parasites on seabass. The prevalence and clinical pathogen of Caligus infection has been described through a sampling of 150 fish from floating cage at different cultured periods. Acute toxic tests with different concentrations of neem oil were carried out on the parasite and fish host. Results revealed that the 96‐hr median lethal concentration (LC₅₀) of Caligus and fish (10.3 ± 2.5 g of body weight) were 2 and 20 ppm respectively. The in vivo test indicated that 10 ppm of neem oil could result in 100% antiparasitic efficacy within 96 hr. These results therapeutically demonstrated the efficacy of neem oil in caligid control.     

Effects of electrolyte enhanced water on culturing giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

In this work, electrolyte enhanced water (EW) was used to determine the effect of EW in culturing freshwater prawns. The giant freshwater prawn juvenile, Macrobrachium rosenbergii, was exposed to different concentrations of EW in experiment 1. The EW was added into the water and labeled as treatment A1 which consists of 1% anolyte and 0.5% catholyte. In the respective treatments, the proportion of anolytes and catolytes are as follows: treatment B1 (1% anolyte and 1% catholyte), treatment C1 (2% anolyte and 0.5% catholyte), treatment D1 (2% anolyte and 1% catholyte), and control (without EW). All these treatments were run in three replicates for each treatment including the control. In the first experiment, the growth of the M. rosenbergii under treatment A1 showed an increased in growth as compared to the control after 56 days of exposure with a significant difference of p?<?0.05. The survival rate of prawns is higher in treatments A1 (73%), B1 (70%), and control (63%) as compared to treatments C1 (53%) and D1 (50%). In the second experiment, the treatment using EW concentration of 1% anolyte and 0.5% catholyte was used as the most suitable concentration for the prawn culturing tested with recirculating aquaculture system (RAS). The treatments used in the second experiment was labeled as A2 (EW), B2 (EW and RAS), C2 (RAS), and control. Treatment B2 showed a higher growth and survival rate and was significantly different to the other treatments. The colony-forming unit (CFU) showed a lower count of bacteria in all experiments that used EW as compared to the control. The concentration of 1% of anolyte and 0.5% of catholyte has shown to improve the growth and survival rate of the M. rosenbergii culture when combined with the RAS. This study showed a potential use of electrolyte enhanced water in culturing giant freshwater prawn.