Finfish Breeding and Hatchery Management

Unit 5 - Fish seed rearing techniques

5.3.2. Closed system

• In the closed system, the source of oxygen is not air, but oxygen which is supplied with a cylinder, into an enclosed space above the water.
• Earlier, sealed metal containers were employed with oxygen successfully for transporting fish spawn and fry involving long duration.
• The containers are made of galvanized iron and measured 45.75cm x 35.36cm, with airtight openings at the top, one to let in oxygen and the other to let out the displaced water.
• In the early 1950s, CIFRI, Barrackpore introduced the 18 l kerosene tins filled with air-tight screw-capped lids for filling, provided with tubes for draining in oxygen from a cylinder and letting out displaced water.
• About 900-1000 fry (1-2 cm long) could be conveniently transported by air for over 20 hr.
• The specially designed Aluminium containers were found most efficient, but considering costs of different types of containers tested, they recommended the latex-rubber bags for commercial use.
• The Department of Fisheries, Maharashtra State gets the credit for introducing polythene bags for the successful transportation of major carp fry.
• The fry (20-25 mm) was transported in polythene bags (840mm x 610mm; thickness 0.0622 cm) inflated with oxygen, kept in kerosene oil tins (18 l), from Calcutta to Bombay.
• It was found that in such bags approximately double the quantity of fry than those transportable in hundies could be shipped.
• Singh (1977) proved that rohu fingerlings need greater quantity of oxygen for transport during the same period as compared to mrigal; the oxygen required for 50 fingerlings of rohu (109-126 mm) for transport during a 12-h period is 1,680 ml against only 475 ml for mrigal (98-100mm) at 31-32^oC.
• Singh et al. (1979) observed that oxygen requirement of silver carp fingerlings is higher than that of grass carp.
• In Karnataka State, carp seed are commonly transported by road in 18 l capacity high density polythene bag containing 1/3 water and 2/3 pure oxygen, sealed and packed in rectangular metal boxes (Basavaraja, 1994).
• The number of seed to be packed in each bag depends upon their size (from 2,000-10,000, 600-700 and 150-200 for spawn (<8mm), fry (8-40mm) and fingerlings (40-150mm), respectively.
• In Karnataka and Andhra Pradesh, fish farmers over the years, have developed a method of transporting fish fry and fingerlings in large (1000 l) sinter plastered tanks, with continuous oxygenation during the journey hours.

A truck being loaded with rectangular tin boxes containing carp seed destined for transportation.


Plastic bags containing fish seed are being loaded to a truck for transportation (Photo Courtesy : Dr Utpal Bhowmick).


Metal boxes containing fish seed are being loaded on to a jeep (Photo Courtesy : Dr Utpal Bhowmick)