Farm and Home Biosecurity
Livestock/Row Crop Producer
Biosecurity Protection for Fish Operations
Producers of trout and salmon have long followed rigorous biosecurity
protocols designed to prevent the spread of fish diseases from one farm to
another, between farmed fish and wild fish, and from pond to pond within a farm.
The bacterial and viral diseases of trout are easily spread and research has
shown that the incidence of diseases is significantly higher on farms that
employ workers that work at more than one production facility. Trout and salmon
are subjected to rigorous health inspections before any fish transfer takes
place. These inspections may involve individual lots of fish, but more commonly
focus on certifying production facilities and their water supplies as free from
specific fish diseases. The protocols for these inspections are mandated by
state and federal law and frequently involve highly sensitive DNA techniques (PCR).
There are no such organized regulations governing the movement of the
warmwater fish. Each state and foreign country may have its own import
regulations but there is no system for routine inspection of warmwater fish
farms. The difference handling of coldwater and warmwater fish diseases
developed because of a historic emphasis by the U.S. Fish and Wildlife Service
on the management of trout and salmon. Since then, warmwater fish have remained
out of the inspection spotlight because of a widespread perception by farmers
and regulators that disease risks associated with the transport of warmwater
fish are not significant. This widely held assumption might not be valid. A
careful examination of the history of some warm water fish diseases provides
ample evidence of disease spread.
Enteric septicemia of catfish (ESC) is the most important disease in the
catfish industry. The disease occurred on an Arkansas fish farm in 1969, but was
not correctly diagnosed until 1978 when 3 cases were reported. By 1985, the
disease was so widespread that diagnostic laboratories reported almost 4,000
cases. Another example is Koi Herpes Virus (KHV). This disease was exported to
the US along with shipments of koi. It spread slowly at first because water
temperatures were not optimal. When spring came and koi ponds warmed, valuable
collections of koi were wiped out all of the US. Clearly there are warmwater
fish diseases with the potential to be just as devastating as those that affect
trout.
Preventing the Introduction of New Diseases
The greatest disease risk facing Arkansas fish producers is the introduction
of new diseases into established farms. Possible mechanisms for disease
introduction vary depending on the fish species involved, but those below
probably present the biggest hazard.
• bringing infected fish onto the farm from another fish farm or from the
wild
• transfer of equipment (seines, aerators, and trucks) between farms
• animal vectors, especially birds
• using contaminated water
Farmers can avoid introducing new diseases by following procedures aimed at
blocking these modes of disease transfer. A comprehensive biosecurity plan
should include the following.
When introducing new fish: Wild fish, fish from other farms, or fish
returned the farm by a distributor should all be considered potential sources of
disease. New fish should be inspected for known diseases before they are brought
onto the farm. While not practical with current catfish production practices,
producers of other fish species should quarantine new fish in ponds or
facilities separated from the rest of the farm by the greatest practical
distance and as far away from existing broodfish stocks as possible. The
duration of the quarantine should be at least several weeks and involve the full
range of spring or fall temperature fluctuations (quarantining fish in the
winter for a disease that only occurs in warm water is not useful). Minnows
returned to producers from dealers should be kept separate from established fish
stocks.
When moving equipment: Drying kills many fish pathogens. When practical,
trucks, seines, and other equipment that has been used for fish from another
facility or from the wild should be rinsed (warm soapy water is even better) and
allowed to dry before re-use. This is especially critical for seines and trucks
that have been used to harvest or transport sick fish. As a mechanism to
transfer disease from farm to farm, a wet mucus-laden seine is almost as
dangerous as the transfer of infected fish.
Animal vectors: The most important animal vectors for fish diseases are
birds. Several species of fish-eating birds carry life stages of parasites (“grubs”)
that infest fish. This risk can be reduced by a bird control program that uses
the most effective legal means to discourage birds from visiting farm ponds (see
your Extension agent or the animal control specialists from USDA-APHIS). The
same parasites that travel in birds also have snails in their life cycles so
chemical or biological control of snail populations is beneficial in species
where grubs are a problem. There is also some evidence that birds may be able to
transmit bacteria or viruses through their droppings. Birds may also drop fish
that they have removed from one body of water into another.
Contaminated water: The safest water for fish production is water pumped
straight from a well to the pond. However, concerns about declining water tables
and pumping costs have raised interest in re-using water and in the use of water
pumped from rivers. Water recirculated within a farm from pond to pond is not
likely to be the source of new pathogens but may enable existing pathogens to
build up larger populations. River water may contain new pathogens not present
on the farm and is the least desirable source of water for fish production. If
river water must be used, it should be pumped through the finest filter
practical and aged in fish-free ponds before use.
Preventing the Establishment and Spread of Disease
When populations of fish quit feeding, behave strangely, or suffer
significant mortality, samples should be submitted to one of the four UAPB Fish
Disease Diagnostic Laboratories. This is especially critical if the disease
appears different than those previously experienced on the farm. Until a
diagnosis is determined, sick fish should be quarantined and any movement of
fish, water, or equipment from the pond should be prevented. If an exotic
disease is diagnosed, the infected fish should be treated or eradicated to
prevent the spread of the disease. Careful adherence to this policy has
prevented the establishment in Arkansas of several potentially devastating
exotic diseases.
Dr. Andy Goodwin
Associate Professor-Fish Health/Pathology
University of Arkansas at Pine Bluff
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