Disinfecting Coded Wire Tagging Equipment

We are unaware of a case of Coded Wire Tagging equipment spreading a disease between fish facilities, but strict disinfection procedures are required before and after tagging to prevent such an occurrence. Disinfection should also be implemented between groups of fish within a facility when signs of disease exist, though tagging should not be conducted during disease outbreaks.


Chlorine solutions are recommended for disinfecting all tagging equipment except the interior mechanisms. To reduce corrosion, alcohol (70 – 90%) is recommended for the interior mechanisms of the Mark IV and other NMT equipment.

Common sources of chlorine are calcium hypochlorite (“HTH”) and sodium hypochlorite (“bleach”). Household bleach comes in a concentration of about 5% so that to achieve the desired concentration (200 ppm) one would dilute 1 oz of bleach in each 2 gallons of water (a ratio of 1:250). Stronger chlorine solutions may be available at fish rearing facilities, in which case you will need to reduce the amount accordingly to achieve 200 ppm.

HTH and bleach are highly toxic to fish but can be neutralized by adding sodium thiosulfate or sodium sulfite to the solution. As a rule of thumb, if a 5% solution of these chlorine compounds is used as a disinfectant, they can be neutralized by adding an equal weight of either chemical. For example, one ounce of 5% bleach added to two gallons of water would be neutralized by one ounce (dry weight) of either sodium sulfite or sodium thiosulfate. If the chlorine solution is stronger, the weight of the neutralizing agent must be increased. As an added precaution, do not pour “neutralized” disinfectant directly into water containing fish.

Before using any disinfectant, read and understand the Material Safety Data Sheets (MSDS) for each product.

Equipment and Supplies

In addition to the disinfectants indicated above, the following equipment and supplies are recommended:

  • Material Safety Data Sheets
  • Two spray bottles for dispensing alcohol and chlorine solutions
  • Tap (pathogen free) water
  • 50 ml syringe with 20 gauge needle
  • Wiping sponge/cloth
  • Cotton tipped applicators (“Q-tips”)
  • A 2 – 3 inch length of blank/excess coded wire
  • CWT tool kit
  • CWT injector instruction manual
  • Paper towels
  • An open container for soaking machine parts
  • A pump and appropriate fittings for circulating disinfectant through a QCD
  • A large open container for holding and catching disinfectant pumped through a QCD
  • Rubber gloves
  • Eye protection
  • Particle masks or respirator

Quality Control Device (QCD)

  1. Attach the QCD to the Mark IV injector, power source, and tap water, allowing the water to run through the device for several minutes. During this period, divert the flow through both gates by activating the solenoid valve by pressing [STEP] on the control panel of the Mark IV.
  2. Using tap water and sponge, wipe down the exterior surfaces of the QCD taking care to remove extraneous material.
  3. Choose a well-ventilated work location. Place the QCD on a clean surface that has been disinfected with a chlorine solution or other suitable disinfectant. With the QCD attached to the Mark IV and power, spray and wipe down the exposed surfaces of the QCD with a chlorine solution including all surfaces of the legs. Remove the cover and repeat the process on the exposed surfaces, including inside the cover, taking care to reach all of the nooks and crannies.
  4. Recirculate a chlorine solution through the QCD using a pump. Prepare enough solution to operate the pump and use a container to catch the solution coming out of the discharge ports. Let the solution recirculate for several minutes while diverting the flow through both gates by activating the solenoid valve. After letting the equipment stand for 15 minutes, rinse the surfaces with tap water and then run tap water through the QCD while again activating the solenoid valve.
  5. Allow the QCD, with cover removed, to dry – in sunlight if possible.

Mark IV Tag Injector

  1. Screw the caps on the electrical outlets on the back of the machine. Using tap water and sponge, wipe down the exterior of the injector taking care to remove extraneous material. Repeat this procedure with the touch switch, power supply and attendant cords.
  2. Choose a well-ventilated work location free from hazards that could ignite alcohol. Place the injector on a clean surface that has been disinfected with the chlorine solution. Wipe all the exterior surfaces with the chlorine solution. Without wetting the electrical connections with the disinfectant, thoroughly wipe the touch switch, power supply and attendant cords.
  3. Open the injector and remove the head mold or needle support tube and their screws, the tagging needle, needle carrier, clamping nut and dismantled cutter. Immerse these parts into a container of chlorine disinfectant. DO NOT USE alcohol on the head molds. Alcohol may damage the surface material.
  4. Immerse tools, and other contents of the kit including the case, into the disinfectant.
  5. Remove the lower drive roller pressure arm and the rear wire guide. An E-clip holds the needle arm on the drive cam. Remove it and the needle arm. Spray the alcohol solution onto the exposed interior surfaces (including the case) taking care to include drive rollers, wire guides, tension spring, drive roller latch (in both up and down positions), hinges, lower drive roller arm, and all screws.
  6. With alcohol wetted Q-tips, thoroughly clean all surfaces and orifices/tubes of the head mold holder, needle carrier clamp, vertical inspection hole, cutter motor drive pin, cutter motor block including hole for cutter pin, and alignment pin. Shift the moving parts to and fro during the process to insure that all surfaces are exposed to the alcohol.
  7. Remove the caps from the electrical outlets and spray with the alcohol solution. Let the alcohol evaporate, then replace the caps once dry. Similarly spray the electrical connections of the power supply and touch switch.
  8. Rinse the soaking injector parts, tools and case in tap water. Remove any debris adhering to the cutter parts. Using a length of tagging wire dipped in alcohol; probe the holes in the cutter sleeve and cutter pin to clear them of any material. Insert the tagging needle into the 20-gauge barrel of an alcohol loaded syringe and force a stream through the tagging needle. After removing the hypodermic needle from the loaded syringe, force alcohol through the tagging needle carrier.
  9. Remove the soaking parts and tools from the water, spray with alcohol, and reassemble the parts using disinfected tools. After replacing the 20-gauge hypodermic needle onto the loaded syringe, fit it over the refitted tagging needle and force alcohol through the needle, toward the interior of the injector, until a steady stream reaches through to the drive rollers. Using the same syringe, insert it into the wire guide leading to the drive rollers, and force alcohol through until a steady stream reaches the drive rollers. Allow the equipment to dry in sunlight if possible.

Handheld “Multishot” Injector

  1. Completely disassemble the injector according to the user’s manual.
  2. Use tap water and sponge to remove extraneous material.
  3. Clean all parts in chlorine disinfectant.
  4. Use a piece of tag wire dipped in alcohol to clean the inside of the needle, holes in the cutter pin, holes in the cutter sleeve, and the inside of the feed tube. Use alcohol and cotton swabs as the final cleaning step for all parts (except alcohol should not be applied to the head mold, since alcohol will damage the surface material of the head molds). Dry all surfaces before reassembling; especially the cutter sleeve and cutter pin to prevent corrosion.

V-Detector, T-Wand, Blue Wand

  1. Rinse the surfaces of the detectors with tap water removing any extraneous material in the process.
  2. Place the equipment on a clean, disinfected surface and spray liberally with a chlorine solution.
  3. Allow the equipment to stand for about 15 minutes, rinse again with tap water, and allow to dry in sunlight if possible.

Other tagging equipment

Care must also be taken to disinfect nets, buckets, hoses, boots, rain gear and any other equipment that has come in contact with fish or fish-bearing water that could serve as a “vector for diseases.

AutoFish and Manual Tagging Trailers

Large scale coded wire tagging operations may involve mobile trailers each housing several tagging units. Disinfection of equipment in these trailers is very similar to the previously described procedures, but in most cases domestic water will not be readily available.

Remove extraneous material from the trailer and equipment using a wash down hose and sponge. Wear protective clothing, and conform to other safety precautions, recommended in the MSDS and open all doors and windows. Measure the water into a large container, such as a holding tank or tote. Add the amount of chlorine disinfectant required to achieve the desired concentration. Immerse the main trailer water pump into the container.

Further details about disinfecting tagging trailers are available from individual agencies and in AutoFish System User’s Manual (pdf).