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Post Larval Fitness Parameters
For Litopenaeus vannamei in Project X
Larva obtained for Project X ideally should come from specific pathogen free ( SPF ) broodstock and either from a SPF hatchery or from a High Health Status facility. TSV and WSSV resistance over IHHNV resistance in vannamei is acceptable.
The following conditions should be revised and met :
Size (age): PL8 to PL 10 for shipping and transport purposes, however PL 15 is preferred. This however depends on market conditions and economics. (See below in transport section)
Culture History (stocking density, survival, feeding) : The size/age of shrimp should be cross referenced with their cultivation history to see if they have had a smooth transition through all their larval grow-out stages. One should also check cultivation history to look at feeding regimes and feeds used, use of curative or preventative antibiotics and any other chemical usage during PL cultivation. Survival rates should be revised.
Broodstock / Genetic History: Source of nauplii (SPF broodstock with source history).
Visual Examination : Procedure Preferably prior to shipping revision of any PL deformities, their activity, colour, feeding behaviour and molting .
Wet Mount (biological) : Procedure Revision for protozean fouling, cuticle black spot, BP infection, lipid level in hepatopancreas, gut to muscle ratio, bacterial sepsis, larval mycosis, deformities, bacterial fouling. Possibly an independant laboratory histological analysis.
Stress Test : Procedure Different hatcheries undergo differing stress test methodologies. If one or two parameter (salinity, temperature) is used. >85% survival required.
Transport (Packing time, Parameters, transport density, time, additives): The amount of time taken to pack the shrimp larvae in the hatchery should be noted. Water parameters need to be co-ordinated prior to shipping as some hatcheries can change parameters to suit clients. Shipping temperature is best at around 18°C. Larvae are packed in double plastic shipping bags filled with ten litres of clean water. This water is oxygen saturated and the bag is further inflated with oyygen prior to sealing. Bags are normally shipped two per styrofoam boxes. The number of PL's shipped per bag depends on the transport time and the age of the PL's. Post larvae PL8/10 can be shipped in ten liter bags over 12 hours at a density of 20,000 per bag with good survival rates. One million PL's 8/10 would require fifty bags, twenty five styrofoam boxes and would weigh approximately 550 kilos. PL 15-20's can be shipped at 5,000 per bag up to 12 hours with good survival.
Accompanying Paperwork: For International transports PL's need to be accompanied by appropriate veterinary certificate from exporting country.
Guarantees: Any commercial guarantees would have to be worked out on a per supplier basis. For example, shipping bags with excessive mortalities entitle buyer to credit.