If the outbreak occurs in an open system (a river or creek), eradication will be extremely difficult. Removal of all crayfish from the water body by chemical means, with consequential destruction of other aquatic animals, may be the only viable way to eradicate the infective agent, but this option is likely to be unpalatable to the public. A publicity campaign would be required in order to raise public awareness of the importance of eradication and to educate the public of the need to prevent spread of the pathogen. A precedent for such a large-scale removal of fish exists. In Norway, the chemical rotenone was used to remove all fish from rivers in an attempt to eliminate the skin parasite Gyrodactylus salaris, which had become established in local salmon populations. This was successful in smaller rivers.
Semi-open and semi-closed systems
Many crayfish aquaculture facilities are semi-open systems with fenced ponds or dams, but run-off may enter waterways or ponds. In semi-closed systems, the movement of crayfish can be controlled and there is partial control of the distribution and flow of water.
Closed systems
In closed systems, such as reservoirs, farm dams or aquaculture facilities with no run-off into nearby waterways, both crayfish and water movements can be controlled. If an outbreak occurs in a closed system, eradication may be easier to achieve with less ecological damage.
Prevention of the movement of infected crayfish and the pathogen is the key priority in the event of an outbreak or suspected outbreak. Affected farms, water bodies and rivers must be identified and quarantined without delay.
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John Conar
On April 3, 2012 at 1:43 pm
Would a skin parasite Gyrodactylus salaris affect humans?