INDUCTION AND RECOVERY TIMES FOR TMS

TMS acts on the peripheral nervous system, Afreezing@ the fish, while Marinil acts on the central nervous system, causing the fish to be Ahypnotized@ or Asleepy@ while still able to react. They can be used together in some situations to achieve dual anesthesia, a similar idea compared to human anesthesia.

Some fish culturists have had good success with the use of Marinil as a sedative in the rearing tank. Once the water level is lowered, Marinil is added at 0.1 to 0.3 mg/litre of water. This dose sedates the fish, making them much easier to catch for moving to the anesthetic tank. If Marinil is used as a sedative the dose of TMS may need to be lowered. A small number of fish should be captured in the net and quickly placed into a nearby anesthetic bath containing TMS. Marinil is a prescription drug; consult your veterinarian for further advice on its use. Marinil and TMS have been used together in grading operations. Marinil is often used to calm fish during smolt transfer. Either or both might be used for broodstock handling or fish surgery / tagging.

Stress can also come from the anesthetic bath and the anesthetic itself. It is important that the water in the anesthetic bath be the same temperature as the rearing tank. The water in the bath should be well oxygenated, and should be changed frequently to reduce foaming and mucus build-up and to minimize the amount of debris in the water. Under some water conditions, addition of VIDALIFE may prove beneficial. Fresh anesthetic baths also ensure that the anesthetic dose is maintained. With each batch of fish, TMS levels in the anesthetic are reduced. Lower doses of TMS 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 reduce TMS levels. Anesthetic totes shoulc be plastic or fibreglass. Metal containers must not be used: they react with tricaine to produce harmful byproducts.

TMS 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 TMS. Anesthetic baths can be buffered with sodium bicarbonate to maintain a steady pH from the rearing tank, through anesthesia and into recovery. 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 TMS should bring most anesthetic solutions back to near normal pH. Alternatively, a saturated sodium bicarbonate solution, which usually contains about 10% sodium bicarbonate, can be added at the rate of about 5 ml to each litre of TMS bath solution. Measure the pH of the TMS 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 TMS before adding to the anesthetic bath. Add the TMS first, then add the sodium bicarbonate separately, do not pre-mix. So: measure the pH before you add the TMS (start level). Measure it after you add the TMS. Add sodium bicarbonate until you return the pH to the start level, keeping track of how much you added. Note the amount of bicarbonate you need to add with your dose of TMS, and how much water you have, to simplify making up the next bath that day. Until you get going, always check the pH before you put the fish in.

Fish should be closely monitored for recovery from anesthesia. The recovery tank should be at the same temperature as the source water, and should be well oxygenated. Care should be taken to prevent immobilized fish from stacking up on the bottom. Within minutes, fish should be swimming in the recovery tank. If recovery time is prolonged, the anesthetic dose should be reduced and/or the amount of time in the anesthetic baths should be reduced.

After anesthesia and handling, the fish should not be disturbed until they have resumed normal feeding. High quality feed should be offered and water quality should be kept at optimal conditions. The point is that you can use anesthetics in combination with good handling procedures to reduce stress in your fish. Fish don=t like abrupt changes. When you=re moving fish around for grading, vaccinating, etc., try to keep the temperature, oxygen and pH the same through all steps.

Care during handling and anesthetizing fish can assist in making your fish rearing program a success. Please contact us if you require any further information.