SHRIMP MORTALITY IN HATCHERIES IN SRI LANKA
From: Kishan & Sharm Jayewardene krsj@sltnet.lk
To: shrimp@egroups.com
Sent: June 12, 2000
QUESTION:
In Sri Lanka we have around 70 hatcheries (small-large scale) that supply post larvae to the shrimp farming industry. Since 1995 we have been affected with the White Spot Virus. Though the industry has been hit very badly still around 30-40% of the farms operate at a given time. During the last two months hatcheries have been facing mass mortalities in mysis 3 stage. At Zoea and early mysis stages the larvae do very well but suddenly at mysis 2 the larvae get weak, stop feeding and by mysis 3, 90-100% of the tank is dead. This mass mortality also occurs in some tanks at PL 5-10.
What's strange is that not all tanks are affected, if three tanks are
stocked two of them get affected. Furthermore when tanks are checked we can't see many dead shrimp. Usually June/July/August are the best months to produce monodon here.
Is this a problem faced by hatcheries in other parts of Asia? Has someone found out what is causing this? We would appreciate if anyone can help us with this situation.
Kishan Jayewardene
for the Shrimp Breeders Association of Sri Lanka
***************
COMMENTS:
It sounds like Zoea II syndrome as we call it around America.
Most seed producers have solved the problem by stocking the hatchery in less than 3 days since experience shows that the survival goes down as the stocking period goes beyond 3 days. It is suspected that the mortalities are due to bacteria and vibrio attack, which does not affect so much the population of the early stocked tanks as it does to the later.
Dryout the hatchery and run a few experiments observing the survival to initial stocking, and if the correlation is direct you may try to solve the disinfection process of your system to allow a reduction on the bacteria and vibrio accumulation inside the pipes and elsewhere. Also, the use of probiotics may be useful in this situation.
Jose Martinez
E-mail: farallon1@pananet.com