Why do I need fish anesthetics?
The effects of stress on fish during handling for vaccination, tagging, weight sampling and spawning are important considerations in health and production management. Stress on the fish should be minimized so that they can properly recover from the procedure or respond to the vaccine and return to normal feeding and growth as soon as possible. Fish anesthetics play a large role in reducing stress during any handling.
Which fish anesthetics are approved in my country?
Canada
Anesthetics for fish are prescription drugs in Canada.
Syncaine® is approved for use in salmonids and is available by prescription from your veterinarian. Treated fish must not be slaughtered for use in food for at least 5 days after the latest treatment with this drug at water temperatures of 10 C or greater.
USA
Syncaine (MS-222) is an FDA approved fish anesthetic used for the temporary immobilization of fish, amphibians, and other aquatic cold-blooded animals (poikilotherms). When used there is a 21-day withdrawal period.
All Other Countries
Syncaine is available in a number of other countries. Please contact Syndel for details.
Which anesthetic is best for my fish?
As anesthetics typically fall under the drug legislation in various countries, only approved products should be used. Over the years, many other chemicals have been used as fish anesthetics. These include 2-phenoxyethanol, carbon dioxide, quinaldine, methyl-pentynol, etc. None of these are approved and should not be used with your fish.
The choice of anesthetic and dose is dependent upon many factors including the effect desired, the size and condition of the fish, and the ultimate purpose of the fish. Withdrawal time of the fish anesthetic is of major importance if the fish are for human consumption and this varies depending upon the product, the fish and the water temperature. If the drug is used other than under the approved label directions, the withdrawal time is at the discretion of the veterinarian. The mode of action also affects the choice of anesthetic.
How do you use a fish anesthetic?
Note: This discussion relates only to Syncaine®
After choosing the anesthetic and dose, an appropriate amount of the anesthetic should be dissolved in a small amount of water, and then evenly dispersed throughout the anesthesia bath and well mixed. The fish should be fasted for 24 hours before being anesthetized to reduce contamination of the anesthetic bath.
Anesthetic totes should be plastic or fiberglass. Metal containers must not be used: they react with tricaine to produce harmful byproducts. As there is often variability in effect, always test a few fish before proceeding with mass anesthesia. This variability can result from water quality, fish size, temperature, pH, hardness, species and even the strain of fish.
It is always a good idea to conduct anesthesia in the shade away from UV and direct sunlight as these conditions may cause Tricaine-S/Syncaine® solution to become toxic.
The anesthetic baths should be oxygenated and replaced as they become contaminated or every 2 to 4 hours.
It is not a good idea to overload anesthetic baths with fish because you do not want to prolong anesthesia time.
The ideal situation is to reach anesthesia within 3 to 4 minutes and recovery in 3 to 4 minutes.
The usual dose for Syncaine in the USA is 50 to 80 ppm.
Does fish anesthetic affect Water Quality?
Syncaine® decreases the pH of the anesthetic bath, especially in soft freshwater. The amount of the change depends on the water that is used; some water can buffer against pH changes; other water will show large pH changes with Syncaine®. Anesthetic baths can be buffered with sodium bicarbonate to maintain a steady pH. Each water source has unique characteristics, so the amount of sodium bicarbonate to be added must be determined by measuring the pH.
Sodium bicarbonate can be added to the anesthetic bath as a powder or as a stock solution. As a starting rule-of-thumb, adding twice as much sodium bicarbonate as Syncaine® should bring most anesthetic solutions back to near normal pH. Measure the pH of the Syncaine® solution, add sodium bicarbonate solution and measure the pH again. If the pH is still lower than the rearing tank pH, add more sodium bicarbonate. Once the amount of sodium bicarbonate needed has been established, the same amount can be added each time the anesthetic bath is changed. Check to confirm that the bath is at the right pH. Never mix the sodium bicarbonate with Syncaine® before adding to the anesthetic bath. Add the Syncaine® first, then add the sodium bicarbonate separately, do not pre-mix.
It is important that the recovery of the fish is monitored, and problems corrected. The fish should be returned to high quality conditions and feed as soon as possible.
How many fish can I dose at once?
Before you start, test the anesthetic on a small sub sample of fish. The anesthetic dose should be adjusted so that the fish are anesthetized quickly and are moved along smoothly to the handling or vaccination station. If large numbers of fish are placed in the anesthetic, water quality suffers, monitoring the fish for depth of anesthetic is more difficult and the flow of fish to the handlers is not smooth. The accompanying table of doses, induction and recovery times shows the effects of increasing the anesthetic dose.
Do Fish Anesthetics Lose their effectiveness over time?
With each batch of fish, Syncaine® levels in the anesthetic bath are reduced. Lower doses of Syncaine® in over used baths mean longer times before the fish are anesthetized, resulting in increased stress and prolonged procedure times. Long periods of exposure to UV rays from sunlight can also reduce Syncaine® levels.