Finfish Breeding and Hatchery Management

Unit 5 - Fish seed rearing techniques

5.3.1. Open systems

• Till the late forties of this century, fish seed was mainly transported using the traditional methods.
• Under this method, before transporting to long distances, spawn and fry are conditioned in order to empty their digestive tract and condition them to subsist in a restricted area they are inevitably liable to be subjected to during transport.
• The most common method of conditioning is to store fry in a cloth hapa in ponds or in a still part of the river.
• The period of conditioning depends on the size and health of the spawn, fry and fingerlings.
• During conditioning and transportation, fry and fingerlings should not be handled with bare hands lest the slime and scales covering the body be removed and thereby render them vulnerable to fungal and bacterial infection.
• Traditional method of transporting fry and fingerlings in hundies is practiced in Bengal. A traditional hundi is an earthen vessel, but later aluminium hundies were introduced.
• Though the hundies are of variable size, they are generally of two types, the smaller one of 22cm mouth diameter and 23 l capacity carried as a head load and the other larger one of 23 cm diameter and 32 l capacity used for transport by rail or bicycle or as slings.
• The hundies are filled with water from the same source as the fry and they are stocked at 50,000 in the smaller and 75,000 in the larger ones.
• About 58g of fine silt is sprinkled over the water surface in the hundi.
• During transport the hundies are shaken periodically.
• Addition of silt during transport coagulates the suspended organic pollutant as well as keeps down the zone and extent of pollution.
• The use of pulverized earth, activated charcoal and `Amberlite’ tend to absorb carbon dioxide and ammonia from the medium, consequently increasing the survival of fry.
• Improved open metal containers have increasingly come into use and are known to have an edge over earthen hundies.
• These are round vessels with a wide mouth, which can be closed with perforated pressed in lids, the larger type being 53 cm diameter at the base, 20 cm at the mouth and 38 cm high.
• To prevent denting and effect of insulation, woolen covers are used on the metal containers or the vessel is aerated and kept wet during the journey.
• Transport of carp seed in Aluminium pots mounted on bicycle or tricycle is a common sight in Kolkata.
• Another container traditionally used for the transport of fish fry and fingerlings is galvanized round tin carriers with a flat bottom of about 40-50 l capacity.
• The inner lid is perforated and dish like and it serves well for aeration by cascading down the water splashed into it during transportation.
• In other parts of the country, open method of transportation of fish seed is going out of use mainly because it involves constant vigil and frequent renewal of water on long journeys.
• And also it is not economical to transport bigger fingerlings and adults in small packing units.
  
  

Fish seed being transported to market as a headload (Photo Courtesy : Dr Utpal Bhowmick)

Aluminium pots containing fish seed are transported as slings

Fish seed being transported on a cycle rickshaw