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How to Give a Fish CPR: Our Vet Explains (With Pictures)

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By Dr. Emma Chandley

hand holding Goldfish for Aquaponics Systems

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Dr. Emma Chandley

BVetMed PGCertSAS MRCVS (Veterinarian)

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It is every owner’s worst nightmare to find one of their fish out of water. Knowing what to do (and also what not to do!) in this situation is very important. Cardiopulmonary resuscitation (CPR) is an emergency lifesaving procedure performed when a cardiopulmonary arrest occurs. The goal of CPR in any species is to get the heart pumping blood around the body again and to preserve neurological function.

If you come home to find a fish out of water, it may sadly be the case that your fish has been deprived of oxygen for too long and they will pass away. If they have only been out of the water for a short time, there are a few different things you can try to revive them. This article will discuss these in detail.

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The 7 Steps of Fish CPR

CPR in fish is not the same as in humans. Fish breathe very differently from people. They do still exchange gas but in their own unique way. Fish take water into their mouth and cause it to exit over the gills. The gills are situated behind the fish’s head. When water passes over the gill’s thin walls, oxygen that has been dissolved in the water moves across into the fish’s blood where it is transported to the fish’s cells.

At the same time, carbon dioxide is released back into the water. The gills have a very large surface area, and they have a really good blood supply to maximize the exchange of gasses.

1. Check Your Fish is Alive

Sadly, if your fish has been out of water for too long, they will not be able to be revived as they will have been starved of oxygen. Check your fish over to see if they are alive and if it is worthwhile performing CPR on them. Signs your fish may have passed away will include:

  • No movement at all
  • Concave eyes (curving inwards instead of bulging outwards)
  • Cracks in skin
  • Extreme dryness
  • Gray pupils
  • No sign of a heartbeat
Dead carp fish in the water
Image Credit: Athapet Piruksa, Shutterstock

2. Get Your Fish Back into Some Water

The first thing you need to do is to place your fish back into some water gently. This is not as simple as it sounds though. You should not place them straight back in the tank with other fish. This is because it is likely the other fish will be curious and bother and nip at it, causing more stress. The best thing to do is to take a large clear jug or bowl and place some of the tank water in this, then put the fish in here.

When you pick up the fish, they may feel hard. This is because the fish has been drying out and their muscles may have seized up. Do not attempt to move or bend the fish, this can do more damage. Simply submerge the fish, with minimal contact, into the tank water.

When the fish is in the water, observe them closely to see if they start to breathe again. Some fish that have been out of the water for a short amount of time are able to start breathing normally again and no assistance is required.  If the fish is not breathing or appears to be struggling in any way, more assistance is required.


3. Clean Any Debris Off Your Fish

Very gently wipe any dirt or debris off your fish. Especially around the gill area where it could block the gills. Gently moving your fish around the water can also dislodge any dirt.

Dead goldfish in blue plastic bowl
Image Credit: Mark Brandon, Shutterstock

4. Oxygenate the Gills

Fish out of water may become dried out to the extent they cannot use their gills. If this is the case, you can take a small tool such as a popsicle stick and very gently move the mouth to an open position and move the covers of the gills. Doing this slowly and gently is very important as any strong or aggressive movements will cause more damage.

This opens up the breathing channel from the mouth to the gills and will allow water to flow over them. Often if the fish has been out of water for a longer period of time, simply allowing water to flow through the mouth and over the gills is not enough. There are a few things you can do to attempt to reoxygenate the gills.

You can gently move the fish around to draw water over the gills. This can be done by slowly guiding the fish forward through the water. Never move the fish backwards as this may push water the wrong way over the gills and the force of the water moving may damage them. You can use a small syringe or pipette to gently push water over the gills. Extra care must be taken not to damage the gills as they are very fragile structures.

However you move water over the gills, it cannot be too forceful otherwise you will damage the gills. Always keep this in mind.


5. Rub Your Fish’s Belly Gently

You can also attempt to rub your fish’s tummy to encourage airflow over the gills. Again, this must be done very gently. With one finger, slowly massage the underbelly with small circular movements.

hand holding goldfish
Image Credit: Pavaphon Supanantananont, Shutterstock

6. Increase Oxygen

If at all possible, the next step is to try and increase the amount of oxygen your fish is receiving in the water they are in. This can be done by using an air stone or an air bubbler. You can switch up the settings of an air bubbler so that more bubbles of oxygen are released into the surrounding water.

Hold your fish closer to the highly oxygenated water so that its gills are submerged in it. This will allow them access to more oxygen and may help in reviving them.


7. Monitor Your Fish Closely

If you do manage to get your fish breathing again, unfortunately, you are not out of the woods just yet. The stress of the ordeal can be very detrimental to your fish’s health. Their immune system will not be functioning as well, and they will be prone to infections. Keep a close eye on your fish for the next few days. If you see any signs of illness, contact your vet immediately.

Nymph goldfish in aquarium with plants and pebbles
Image Credit: dien, Shutterstock

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Considerations When Performing CPR

There are some serious ethics to consider when choosing to perform CPR on a fish. It can be a controversial act to carry out. The decision to commence CPR is normally a medical judgment made by a professional in a hospital setting. The decision to start CPR untrained and at home with no medical equipment or advice is often a dangerous one. The fish cannot opt in or out themselves and lots of fish owners have had zero experience of resuscitation methods. There is a high chance that more damage than good may be done by the untrained hand.

Another serious point is that the fish will be in considerable pain and discomfort when they are out of the water. Performing CPR is extremely distressing for them and can be painful. In a lot of cases, as the fish has suffered so much already, often the kindest thing to do is to euthanize them. Attempting CPR may seem like the right thing to do, but if the fish suffers unduly because of this, it is inhumane.

Another issue is that it is very difficult to gauge if a fish is in pain or not. Cats and dogs have much more obvious ways of telling us if they are distressed or in pain. With fish, it is much more subtle, and they hardly show any signs at all. Therefore, it is not obvious if our fish are suffering so we don’t actually know what damage we are doing by performing CPR.

In a lot of cases, where fish have been out of water for a prolonged period, or if they have had an injury or illness in the tank which renders them unable to breathe, the kindest option is to perform humane euthanasia.

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Frequently Asked Questions

Do fish have lungs?

Fish do not have lungs in the same way humans and other animals do. Fish have gills instead. Fish take water into their mouths, forcing it over the gills. Dissolved oxygen is absorbed from the water and dissolved carbon dioxide is released into the water. This is how fish exchange gasses. The gills have a large surface area and are extremely well vascularised, meaning they are well adapted for oxygen extraction.

Can you do chest compressions on a fish?

No, it is not possible to perform chest compressions on a fish and this can be very dangerous. Fish do not have lungs so chest compressions will not work in the same way that they do in humans. You can gently rub a fish’s underbelly to encourage water flow over the gills, but it is not recommended to do chest compressions.

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Conclusion

Performing CPR on fish is a controversial subject. If you find your fish unable to breathe, there are a few things you can try to revive them, however, you may be doing more damage than good. If your fish has not been out of the water long and has no other signs of injury or illness the prognosis is better. If the fish has been out of water for a longer period or is sick or injured, the kindest option is likely to be euthanasia.


Featured Image Credit: panpilai paipa, Shutterstock

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