VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

METHODS OF EYE STALK ABLATION

• Several methods are available for the removal of eye stalk. They are (i) cutting the eye stalk near the base with a pair of scissors followed by sealing with a pencil-type soldering iron (electrocauterisation); (ii) pinching of eye stalks and squeezing of eye ball contents out and (iii) incision of eye ball followed by enucleation of contents. Among the various methods, electrocauterisation is favoured as it seals the cut instantly, avoiding bleeding and ensures cent per cent survival.
• For the procurement of brood stock for inducement, some of the marine shrimp reared in ponds for harvestable size may be allowed to grow for a further period of one year before subjecting them for eye stalk ablation, though the age of F. indicus and P. monodon at first maturity is only 4-6 months and 5-15 months respectively. The eye stalk ablation is carried out only in female and not in male. For eye stalk ablation, F. indicus with a carapace length of 30 mm (total length, 150 mm; weight >20 g) and P. monodon with a carapace length of 50-80 mm (total length 200 mm and weight <100 g) are normally selected. Before removing the eye stalks, the brood stock are kept in large plastic pools containing filtered seawater of 33 ppt (parts per thousand). After about 24 hours, the eye stalks are removed in the female using electrocauterisation technique. The ablated females and unablated males are then kept at 2:1 in larger circular plastic lined pools, in which the seawater is made to circulate through subgravel filter by air lifts. The breeders are fed ad libitium using chooped fish or clam meat. The temperature, salinity and pH of the medium are maintained at 28 ⁰C, 32 ppt and 8-8.2 respectively.
• Generally the mating and impregnation are ensured in the marine shrimp if the males and females are kept separately in two tanks and the females are introduced into the female tank when they are about to moult. The separation of sexes seem to enhance the attraction between them and facilitate early spawning.