Other transport methods
Plastic bags may be used to transport small amounts of fish, for instance to transport fish for lake cultivation and for transport of ornamental fish. A common size of transport bags is 85 cm × 60 cm. Thick polyethylene (PE) is used to make the bags resistant to puncturing. The bag is normally filled with between one-quarter and one-third of its volume with water before the fish are loaded. Air is then removed from the bag by pressing it together, which is then filled with pure oxygen until it assumes a balloon like form. The atmosphere over the water in the bag will then be pure oxygen. Cooling of the plastic bag minimizes the oxygen consumption of the fish and maximizes the duration of oxygen supply. Using ice on top of the bag, and not exposing the bag to direct sunlight may help with this. During transportation it is recommended that the bag is shaken from time to time to mix the oxygen that is in the atmosphere above into the water. The duration of the journey using this method depends directly on the fish density and their oxygen consumption. For example, a density of 1 kg salmon smolt per 3–4 l of water and 10 l of pure oxygen in plastic bags at 5°C has been used for air transportation for a couple of hours.
An alternative to plastic bags is
plastic containers. Here also the containers are filled with approximately
one-third of water and fish, above which there is a pure oxygen atmosphere.
Special equipment is required to remove the air from the can and replace it
with pure oxygen.
Special types of tractor-trailers designed for fish transport can be used for short journeys (Fig. 18.6). Goods wagons equipped with tanks for live fish transport have also been tried for railway transport.
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