Larvae biosecurity

Abstract This chapter looks at the issues surrounding health of finfish and shellfish larvae in the aquaculture environment. The chapter will examine issues such as biosecurity to see how it forms the cornerstone of effective hatchery management and how problems can arise when biosecnrity fails. Then the chapter looks at how the health of the larvae can be manipnlated and how the larvae can be protected from potential pathogens by good management. 

Key words larvae, vaccine, immmnnostimnlant, thymus, biosecurity, immunity, live feeds, hatchery, water quality, health. 

Providing these biofilters only contain beneficial bacteria that are involved in this breakdown of ammonia then they pose little risk to the larvae. If the biosecurity breaks down due to say, operator error, and a pathogen is introduced it may become established in the biofilm with the biofilter and become a more permanent member of the bacterial community. In this situation, there is the potential for the filter to shed pathogens into the water column with subsequent infection of the production larvae. This situation is very difficult to eradicate. Control measures may include installation of UV or ozone after the biofilters to kill any shed bacteria before the water enters the production area or the breakdown and sterilization of the larval production system. 

Fig. 8.1 Model of hatchery system showing the four interlinking microbial compartments of the hatchery tank 1. sea water (water column) 2. surfaces (walls and pipework) on which microbial biofilms form 3. larvae and 4. larval feeds (live and/or formulated). Major inputs, each representing a potential biosecurity threat, include the sea water, the larvae - added on day of stocking, the feed - added on a frequent and daily basis, and other vectors such as aerosols, staff and equipment.

This rapid expansion of white shrimp production in Asia resulted from widespread availability of High Health PL derived from SPF broodstock. To produce High Health PL requires use of SPF broodstock combined with good biosecurity at the hatchery. If shrimp larvae produced from SPF broodstock are infected with disease during their hatchery phase, the benefits of using SPF shrimp are lost. Thus best use of SPF broodstock in a shrimp hatchery requires special attention to biosecurity to produce true SPF or High Health PL. 

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