Dedicated To Tribal Aquaculture Programs
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Biosecurity
By Syndel Laboratories (Canada), (800) 663-2282, Western Chemical, (800) 283-5292
Biosecurity involves the exclusion of disease-causing organisms from the environment. This is particularly important in fish production and is achieved by the use of both external and internal biosecurity barriers:
Critical Control Point External Barrier to Establish Incoming Water
* Use a pathogen-free water source.
* When possible select a water source free of concerns from indigenous species.Egg & Fish Movements
* Prevent movements of older fish or eggs of questionable hygiene or health.
* If in question, apply appropriate quarantine procedures and diagnostics.Facility Access
* Incorporate fencing and signage.
* Direct new deliveries and visitors (away from the facility) to an isolation zone.Visitors
* Provide protective clothing that undergoes designated washing and disinfection.
* Use foot baths and hand hygiene stations.
* Identify high risk people and practices.Pest & Predator Control
* Establish a predator management program as predators can spread disease and stress fish.
Critical Control Point Internal Barrier to Establish Designated Zones
* Identify fish groups that may have an increased susceptibility or resistance and assign a risk status for each group .
* Set up isolation and disinfection procedures for these units/zones.Sanitary Measures for Each Zone
* Assign protective clothing for each specific zone/unit that undergoes designated washing and disinfection.
* Conveniently locate foot dips and hand hygiene stations.General Traffic Movement
* Try to move from high risk zones to lower risk zones, high to low health status, younger to older fish and from inside to outside.
Equipment Concerns
* Assign separate equipment (cleaning tools) for each zone, unit or tank.
* Always start each task with disinfected equipment and disinfect equipment if moved between zones or tanks.High Risk Activities
* Remove sick and dead fish carefully and dispose of correctly to avoid cross-contamination.
* Establish an area for service providers to work and clean equipment.One of the challenges faced by aquaculturists is to offer all the life stages of their animals proper sanitary conditions and biosecurity. A comprehensive biosecurity program should be in place. This is essential in combating and preventing disease. Routine use of hand disinfection and footbaths is mandatory. With the rapid increase in intensive aquaculture, the need for disinfectants has also increased. Entry and growth of pathogens must be minimized through use of disinfectants in water, on tanks and equipment, and on eggs. Disinfectants used in aquaculture are aimed at all types of infectious agents (including bacteria, fungi, viruses and protozoa). Disinfectants kill disease causing organisms by releasing proper amounts of chlorine or iodine or other compounds.
The disinfectant must come into direct contact with the organism. It is important that surfaces be clean of organic matter before disinfection This is best done by physically cleaning the surfaces with soap and water prior to using the disinfectant. Control of parasites, bacteria, fungi and viruses are greatly enhanced by the use of the following products:
- is an easy to use, environmentally friendly, general disinfectant.
- is a specially buffered, non-staining, non-corrosive, aqueous iodine solution used by fish and shrimp farm personnel as a general disinfectant on equipment, tanks, nets, hands and clothing in hatcheries and at farm sites. OVADINE may also be used to disinfect fish and shrimp eggs and shrimp nauplii.
- is a fast acting disinfectant that has been shown to be effective against many gram-positive and gram-negative bacteria and fungi.
GENERAL DISINFECTANT
- A 250 ppm available iodine solution is made by diluting 25 ml OVADINE to 1 litre with clean water. Use as a dip or bath.
- Wash items that are heavily contaminated with soil or organic debris before disinfecting with OVADINE.
- A change in the solution color from dark brown to light yellow indicates loss of activity. Ideally, the free iodine concentration should be monitored during treatment. Renew by using a fresh solution of OVADINE.
FISH EGG DISINFECTANT (when using dry fertilization method)
- Conditions such as the organic content of water and the mass of the fish eggs vary, thus the number of eggs treated can vary widely.
- Place eggs into a 100 ppm free iodine solution of 0VADINE for ten minutes. A suitable ratio is 1 volume of eggs to 10 volumes of this solution.
- A 100 ppm free iodine solution is made by diluting 10 ml OVADINE to 1 litre with clean water.
- Rinse eggs, fertilize and place into incubation containers.
CHOOSING THE RIGHT EGG DISINFECTANT
By Jim Brackett and Paul Casey
Reprinted Courtesy of Northern Aquaculture, October 2003Vertical transmission of disease is perhaps the most important vector of disease transfer that proper biosecurity measures can eliminate. Brood fish generally come from an environment were they have been constantly exposed to pathogens and are therefore highly likely to be carriers of infective agents. Although they are not affecting the adult fish, these organisms can have devastating effects if transferred to the next generation.
The transfer from one generation to the other can happen in two ways: on the egg and in the egg. For a disease like BKD that is transferred in the egg, rigorous screening and discarding of all eggs from positive fish is a harsh but necessary biosecurity measure. However, for many other pathogens the route of infection is on the eggs and then into the fry when they hatch. Such pathogens are easily eliminated with proper egg disinfection.
Egg disinfection is a very specialized biosecurity application and, as such, the aquaculturists should choose an equally specialized product. Salmonid eggs are generally in clean, fresh water, consequently, there is no need for concerns over excessive organic material, but there is cause for concern for the effect a disinfectant may have on the eggs. Therefore, there is no need for surfactants, solvents or detergents to strip away excess organic material. What is needed is something that will kill the pathogen but not the egg or affect the eggshell.
Polyvinylpyrrolidone iodine (PVPI) products have been used for many years for this purpose and are highly effective against pathogens commonly affecting salmonid eggs. However, some of these products contain detergents or strong acids that, although helpful in general disinfection, are not helpful for eggshell quality.
When disinfecting eggs with a PVPI solution, aquaculturists should also look for a product with a neutral pH that will not affect water chemistry.
The highly efficacious nature of iodine-based products has led them to being used as general disinfectants. Recent work at research facilities has shown that many iodine products are not effective against some pathogenic organisms in everyday aquaculture applications. However, these products where never designed for general disinfection. In most cases, they were specifically formulated for applications such as disinfecting the udders of dairy cows or fish eggs and many were formulated for use in hospital applications.
Once in incubation after initial disinfection, routine treatment for fungus will also have the beneficial affect of killing anything that might have survived or slipped past initial disinfection.
The production cycle starts with eggs, but those eggs often come from filthy parents. Broodstock screening and proper choice and application of an egg disinfection will ensure that disease is not transferred to the next generation.
The recent outbreak of VHS in the Great Lakes region has highlighted the need for effective Biosecurity programs at all levels. Disinfection is a critical component of Biosecurity programs which reduce the risks of moving viruses and other pathogens between sites. But to be effective, disinfectants for fish disease control programs must be designed to work under the conditions faced in aquatic environments. Many common disinfectants, such as bleach or iodine's, are not the best choices under these conditions. The need for a disinfectant specifically formulated for aquatic environments is what lead DuPont Animal Health Solutions and Vetoquinol Canada to develop Virkon® Aquatic. Virkon® Aquatic is safe and easy to use and is proven effective for killing rhabdoviruses (VHS, IHN, SVC), as well as bacteria, fungi, & molds. It is specifically designed for disinfection of surfaces such as boats, equipment, netting, and tanks. Virkon® Aquatic is formulated to work with comparatively short contact times and in the presence of organic materials. It is environmentally friendly and has a great operator safety profile. The formulation, specially designed for aquatic applications, has met the stringent requirements of Health Canada and the US EPA. Virkon® Aquatic is unique in having label indications and instructions specifically for aquatic applications in both countries.
- is an environmentally friendly, easy to use, general sanitizer.
- is a specially blended pink powder that is readily soluble, has a faint lemon smell and has color indicating potency
- is a fast acting disinfectant that has been shown to be effective against a wide range of bacteria, fungi and viruses
- Formulation specially designed for fish culture
- Meets the stringent requirements of both Health Canada and the US EPA.
- Independently proven broad-spectrum efficacy against a wide range of fish pathogens.
- Fast acting
- Environmentally friendly
- Exceptional safety profile
- New convenient 10 kg size
Transportation of Fish in Bags
by L. Swann, Illinois-Indiana Sea Grant Program, Purdue University, West Lafayette, INIntroduction
Fish, shellfish, and plants often are transported in sealed plastic bags containing small quantities of water and pure oxygen. Bag shipment requires placing a prescribed weight of fish in 1.5 to 2 gallons of water in 3 ml polyethylene bags, 18 by 32 inches. Excess air is removed from the bag and replaced with pure oxygen. The bag is sealed, placed in an insulated container and finally into a cardboard shipping box and shipped. Bag shipment may be the best choice for the shipper for several reasons. First, very small fish and fry could be damaged by being shipped in large tanks. Second, due to the extreme distances involved, bag shipment may offer economic advantages over standard tank transportation. This fact sheet will focus-on transport of fish. With minor modifications the techniques and principals discussed also apply to shellfish.
Water Quality During Shipping
Fish health is affected by changes in water quality parameters while in the plastic bags during the transportation process. The parameters to be considered are temperature, dissolved oxygen, pH, carbon dioxide, ammonia, and the salt balance of the fish’s blood. The rate of change of each parameter is affected by the weight and size of fish to be transported and the duration of transport.
Temperature
Fish are cold-blooded, so the metabolic rate of fish is affected by the temperature of the environment. The metabolic rate of fish will double for each 18°F increase in temperature and be reduced by half for each 18°F decrease in temperature. A reduced metabolic rate will decrease the oxygen consumption, ammonia production, and carbon dioxide production. Therefore, it is essential to transport fish at low temperatures. For cool and warm water species a temperature of 55° to 60°F is recommended. For species such as tilapia and red drum, temperatures should be nearer to 60°F. Cold water fish, such as trout, inhabit colder water and should be transported at even colder temperatures, such as 45° to 50°F. To achieve the desired transport temperature, fish should be held in tanks of cool water. By holding the fish in tanks for two days, the water temperature can be gradually reduced by adding cool water. After loading the fish into bags, final decreases and maintenance of temperatures during transport can be accomplished by adding ice or (more commonly) gel packs. Ice or gel packs often are used during transport, especially over longer transport periods that might allow increases in temperature. One-half pound of ice will reduce the temperature of one gallon of water by about 10°F. Insulated Styrofoam shipping boxes also are used to prevent outside temperatures from affecting the temperature of transport water. In some instances, 20 to 40 quart coolers are used for transport.
Dissolved Oxygen
The most important single factor in transporting fish is the provision of adequate concentrations of dissolved oxygen (DO). The importance of supplying adequate levels of DO cannot be overemphasized. Failure to do so results in severe stress which may contribute to fish kill two to three days after transport. The amount of oxygen that can be dissolved in fresh water is based primarily on water temperature. The water is referred to as 100% saturated when the upper saturation level is reached. DO saturation is higher for cool water than for warm water. For example, at sea level DO saturation of 45°F water is 12.1 parts per million (ppm) but at 60°F saturation is 10.0 ppm. Because pure oxygen is used during bag transport, DO levels in the water will be saturated and the low oxygen levels usually will not be a problem unless the bag is improperly sealed or develops holes caused by the spines of large fish.
It is important to have a 75 percent volume of oxygen in the bag to insure adequate diffusion of oxygen at the surface of the water.
The quantity of hydrogen ions in the water will determine if it is acidic or basic. The scale for measuring the degree of acidity is called the pH scale, which ranges from 1 to 14. A value of 7 is considered neutral, neither acidic nor basic; values below 7 are considered acidic; above 7 basic. The acceptable range for fish growth is between pH 6.5 and 9.0 The pH of water will be influence by the alkalinity (buffering capacity) and the amount of free carbon dioxide. The pH of the transport water will also affect the toxicity of ammonia. Even in well-buffered transport water the pH will sometimes decrease by one pH unit.
Carbon Dioxide
As fish respire they produce carbon dioxide as a by-product. Carbon dioxide reacts with water to form a weak acid. This weak acid will in turn decrease the pH of the water. High levels of carbon dioxide (greater than 20 ppm) will interfere with the oxygen uptake in the fish’s blood. High levels of carbon dioxide sometimes are found in well water. Excess carbon dioxide in well water can be reduced by mechanical aeration or by passing the water through a degassing column.
Ammonia
Ammonia build up occurs in transport water as a result of fish metabolism and, to a lesser extent, bacterial action on fish waste excreted into the water. Two forms of ammonia occur in transport water: ionized (NH4+), and unionized (NH3). Unlike the ionized form, the un-ionized form of ammonia is extremely toxic at concentrations as low as 0.2 ppm. In tests for ammonia, both forms are grouped together as "total ammonia nitrogen" (TAN). The percent of ammonia that is unionized will depend on both temperature and pH. Total ammonia concentrations may reach more than 14 ppm during transport. However, the percent of the total ammonia which is un-ionized at pH 6.5 and 55°F is only 0.07 percent. Therefore, the un-ionized ammonia concentration at 14 ppm is 14x 0.0007=0.0098 ppm. Unionized concentrations greater than 0.05 ppm should be handled with caution. The easiest way to reduce toxic ammonia buildup in transport water is to lower the temperature of the transport water and to stop feeding several days before transporting. Fish up to eight inches long should not be fed for 48 hours before loading and transporting and those larger than eight inches should not be fed for 72 hours before transporting.
Chemical Additives
Numerous chemical additives can be added to the transport water to alleviate several problems associated with transporting fish in bags. Since overdoses of chemicals can cause death, care must be taken when measuring the dosage of each chemical. It is essential to double check every calculation and to use an accurate balance when weighing chemicals. The most common chemical added to transport water is salt (NaCl). Salt is used to relieve stress associated with maintaining a water balance in the fish. Freshwater fish have a blood salt concentration higher than the salts of the transport water. As a result, the fish are continually losing salts to the surrounding water. Concentrations of 5,000 ppm (0.5 percent) are commonly used. A 5,000 ppm concentration can be made by adding 19 grams (one tablespoon) of salt per gallon to water used during transport. Use non-iodized salt that contains no anti-caking compounds. Canning salt is a good example. If the alkalinity of the transport water is less than 100 ppm, some type of buffering compound should be added to the water. Properly buffered water will help remove freed carbon dioxide which causes drops in pH. Sodium bicarbonate (Na2CO3) is one of the fastest reacting buffers and should be added at a rate of 1 g/gal. of water. Finally, the fish will suffer time stress because they are transported in crowded conditions. Sometimes a chemical anesthetic may be beneficial by producing a light sedation. The only anesthetic approved by Food and Drug Administration (FDA) for food fish is Finquel/Tricaine (tricaine methanesulfonate). Finquel may be used at a rate of 0.06 to 0.25 g/ gal. of water.
Carrying Capacity
The maximum weight of fish that can be safely transported within a given period of time is the carrying capacity. The carrying capacity depends on the duration of haul, water temperature, fish’ size, and fish species. If water quality conditions such as temperature, oxygen, carbon dioxide, alkalinity, and ammonia are constant, then carrying capacity will depend on the fish species. In general, fewer pounds of smaller fish can be transported per gallon of water than larger fish. General carrying capacity guideline are given in Table 1. It is important that first time or experienced shippers handling a new species test-run a batch before undertaking a large shipment.
Transport Procedure
Days before the fish are loaded and transported, the shipper should determine the carrier to be used, time of departure, time of arrival, and shipping costs. This information needs to be communicated to the receiver well before the shipping date. All loading should be planned to allow boxes to be shipped as soon after loading as possible. With proper planning, unnecessary delays in delivery and pickup can be avoided. The receiver is responsible for contacting the shipper if any deaths occur.
Table 1. Carrying capacity (in pounds) of warm water fish transported in 18*32" polyethylene bags containing 2 gallons of water. Water should be moderately hard (80-100ppm total hardness) and have a temperature range of 55-60°F.
Carrying Capacity (lbs) for Transport Period in Hours
Length in Inches Eggs Yolk-sac
Swim-up
.5
1.0
2.0
3.0
Large Fish
Source of information on carrying capacity is from Dupree and Hunter 1984.
Procedure for shipping fish:
1. Carefully add the proper weight of fish to 1.5-2.0 gal. of clean high quality water. Water contained in the bag needs to be within two degrees of the holding water temperature. Chemicals, if any, need to be added at this time.
2. Deflate bag to remove air and then fill with pure oxygen. Approximately 75% of the volume in the bag should be oxygen.
3. Twist mouth of bag tightly and secure with heavy-duty rubber bands. Castration rings or heat sealing may also be used. Place bag inside a second bag, which has a frozen gel pack, and seal the bag.
4. Place the sealed bag inside a cardboard shipping box and seal the box. The shipping box must be clearly labeled "Live Fish," with the name and address of the shipper and receiver displayed prominently. In the case of trips which may expose the bags to extremes of heat or cold, the bags may need to be placed inside a styrofoam cooler before being packed into the shipping box.
Procedure for unpacking fish:
Unpacking is as important as packing fish in bags. Guidelines for proper unpacking are as follows.
1. Float unopened bags in a shaded area of the receiving water for at least 30 minutes to - allow temperate to equalize. . Check water temperature and watch for mortalities,
2. Open bags and add 2-3 gal. of receiving water to the bag.
3. Gently and slowly pour fish into the receiving water.
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