34 DECEMBER 2012 • WORLD AQUACULTURE • WWW.WAS.ORG landing quay, which should also be closed for direct access to the farm areas. There should be a parking area outside the smolt farm area for private cars and small delivery trucks. Larger trucks should be directed through a delivery gateway into the farm area. Large trucks bringing equipment, feed and other supplies to more than one farm in the same transport should not be allowed to take products, packing or other items from the farm when in transit. Delivery of goods by boat has a biosecurity risk comparable to that of a truck and the same precautions should be applied. The cargo itself, delivered by trucks and boats, will generally have a negligible biosecurity risk. Admission of personnel into the fish production areas should be possible only through locks. The personnel locks should represent a defined border between the outer risk area and the inner clean area. All personnel passing this border should change shoes. Alternatively visitors may be supplied with strong plastic shoe coverings and disinfection foot baths may be a supplement but not a substitute. Working staff should change outer clothing to pull-on clothes or coveralls. Visitors may alternatively use disposable coats. Wash basins and dispensers with hand disinfectants should be placed at the border and use should be mandatory. Visitors should not be allowed admission through the lock, unless being followed by a staff member who is responsible for implementation of hygienic procedures. Personnel who have been at other aquaculture sites have the highest risk of carrying infectious material. This category includes smolt buyers, consultants, controllers from the authorities, fish health personnel, and vaccinators. The groups of particular concern are those handling fish material. They should have their own strict procedures for decontamination of equipment used at different sites. Different tools and equipment should in general not be used on more than one fish farm, thus eliminating any biosecurity risk. However, some expensive and specialized technologies, such as machinery for automatic vaccination, are often used at several sites and must be constructed to facilitate effective disinfection. There is also the risk of spreading infections within a farm, between tanks or departments, if cleaning equipment and measuring apparatus for oxygen and pH are used in different units. Predator and scavenger birds (e.g., seagulls and herons) and animals (e.g., mink) may visit different fish farms and also feed on wild fish material, and may carry seawater and biological material containing pathogens between sites. Some fish pathogenic organisms may survive the passage through a bird’s digestive tract (Willumsen 1898). Indoor production of smolts excludes, to a great extent, problems with birds and animals spreading infections to smolt farms, but out-door tanks close to shore may be easily accessible. Feed is not typically included as a vector in a biosecurity sense. The risks from commercial dry pellets containing fish pathogenic organisms are estimated to be negligible because the production process applies high temperatures. Nonetheless, fish feed may be exposed to birds and animals during storage and in this way act as a vector. Rodents and passerine birds do not have a significant radius of action but faecal contamination of feed from seagulls might constitute a risk. Indoor or tank storage of feed should eliminate this problem. The risk levels and control points suggested aim at a typical Norwegian smolt production system. However, biosecurity plans and risk levels must be adapted to the actual situation when other systems are used. For instance, if fry are taken into a smolt farm rather than eggs, the risk level will increase. Raising smolts in net pens in lakes has been quite common in Chile and Scotland, causing potentially more contact both towards predators and wild fish. In Norway, raising smolts in large tanks to larger sizes (up to 1 kg) before transferring them to a sea site has been considered. Such production requires a seawater supply of such large volumes that effective disinfection is not realistic. The biosecurity status will then approach that of an ordinary sea farm. Sea Farm — Production of Market-Size Fish The important characteristic of sea-site production of marketsize fish is that there is a land-based station for storage of various equipment. At the land station, there may be systems to handle dead fish, including destruction or disinfection. The land-based station should be demarcated from the surroundings with fences and gates in the same way as a smolt farm and with control of all visitors. Usually there is some distance from the land station to a floating platform with net pens housing the fish. Use of commercially available dry pellets is the dominant system of feeding. There is a continuous flow-through of seawater because of natural currents, such as tides. A production unit for farm animals can be more or less isolated from the surroundings from a biosecurity perspective and this is also to a great extent the situation for a freshwater smolt farm. However, a sea site cannot be strictly segregated from the surrounding water. This implies that biosecurity thinking relating to this production system must be adapted to a less controllable reality. The potential sources of entry for pathogens are to a great extent the same as for a smolt farm; however, the level of risk for each factor is different. Because of the challenging biosecurity situation for sea farms, the prevalence of most endemic infectious diseases is much greater than in smolt farms (Norwegian Veterinary Institute 2011). Live fish taken to a sea-site as smolts. Documentation of health status should be given as health certificates that report: • Health control program served by authorized fish health personnel, including veterinarians, • Disease outbreaks during the freshwater phase, • Documentation of vaccination status is essential, being of great importance to reduce the risk of catching endemic infections in sea-water, and In general, the water supply is considered to constitute the greatest risk for introduction of pathogens to a smolt farm. The risk level varies significantly with type of water source, depending on the fish populations inhabiting the water. However, no water treatment systems have the capacity to eliminate microorganisms completely, only to reduce the infectious load substantially.
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