Preparation for transport
Since the duration of transport is normally quite long, several hours at least, it is important to prepare the fish beforehand. The fish must be in good conditions and should be starved before being transported to empty the stomach and digestive system and hence reduce the release of waste meta-bolic products that cause the quality of the trans-port water to deteriorate. Starving the fish will also reduce the metabolic rate and hence oxygen consumption and secretion of ammonia and carbon dioxide during transport. The length of the starvation period needed depends on the water tempera-ture and the fish species, but is 24 hours or more.
Internal transport, size grading and other handling must be carried out in anticipation of trans-port; the fish must be fully recovered from the stress that these actions involve before being transported. Loading the fish into the transport container must be performed in a manner that affects the fish as little as possible and minimizes stress. After loading it is also important to expose the fish to as little stress as possible to keep recovery times short.
The water used in the transport equipment must have similar characteristics to the water quality that the fish are used to so that they are not exposed to a new stressor. Variations between the temperature of the farming water and that of the transport water must also be avoided to minimize stress to the fish. Normally a reduced water temperature during fish transport is beneficial because the metabolic rate, and hence oxygen consumption and the release of metabolic products such as ammonia and carbon dioxide, will be reduced. Furthermore, the content of available oxygen in the water will increase. However, this may stress the fish unnecessarily, and some warm water species will also die if the temperature is too low. Whether it is appropriate for the transport water to be chilled by adding ice, for instance, must be checked with regard to the transported species.
Fish may be more vulnerable during some life stages than others; for instance, transport of salmon smolt during smoltification, when the scales are loose. Special care must be taken when transporting fish in such situations.