Photo credit: Hai DO Xuan (Vietnam)
Review: Hai DO Xuan and Abdel Rahman El Gamal (Founder of the website)
The inserted picture shows the nursing of cobia (Rachycentron canadum) in Vietnam using green water in a semi-intensive rearing method. This method has been developed in 2005 and got adopted in private hatcheries especially those located in Khanh-hoa province. In this method, relatively large out-door tanks supplied with green water are used.
Typically, cobia larvae are reared first in indoor tanks where they are fed on rotifers for the first feeding stage. In out-door nursing phase as shown in the inserted picture is done in out-door ponds (tanks) with abundant natural zooplankton, mainly copepods is adopted as a means of reducing the cost of live food production.
Before the introduction of the larvae, the out-door ponds are filled up with filtered sea water and then fertilized for enhancing the growth of plankton as larvae rely primarily on zooplankton of the appropriate size as they grow. The density of natural food in nursery tanks is constantly monitored and timely supplementation by natural food from outside sources takes place whenever needed. As soon as the cobia larvae reach more than 3 cm in length, they are transferred to tanks again for weaning.