Quality contaminant free algal feed is crucial for any oyster hatchery as any microbial contaminant will affect the larval growth and lead to mass mortality. To avoid this, we follow

stringent sterilisation techniques in our inhouse algal feed production unit.

[Note: Algae in general refers to a broader group of aquatic photosynthetic organisms. For oyster larval feed, we use microalgae which are single cellular microscopic eukaryotic

organisms]

There are two main types of algae we use in our hatchery: a) Isochrysis sp. b) Chaetoceros sp. Isochrysis sp. are 5-6 µm in length whereas Chaetoceros sp. are larger in size and can be up to 50 µm. Both the taxa are considered widely as an excellent feed for bivalve larvae. Pure and fresh Isochrysis is used as a feed for the initial stages of larval culture, whereas a mixture diet of Isochrysis sp. and Chaetoceros sp. is used for the later larval stages. Briefly, we have three scales of

algal culture – Primary, Secondary and Tertiary. Primary culture is maintained highly sterile (using autoclaved sea water and aseptic culturing techniques in incubation chamber) and is the starting material for our secondary and tertiary cultures. Typically, primary culture is in the range of few milli litres to a litre. Secondary culture is in the range of 2 to 10 litres. This stage is still maintained sterile by using boiled water and the system is not in incubation chambers, rather sterile air is used for culturing. Tertiary culture is in the range of 20+ litres. The sea water is sterilised by boiling and further the tanks are not stringently maintained sterile. However, the tertiary culture is also monitored for microbial contamination.