What is the temperature of your pond? Can you bring this fish inside? It looks like this fish got himself caught on something and it pulled a couple of scales. Right now their is no infection. The problem is there is nothing that you can do for the fish in the probably water temperature of your pond and over the winter very little healing will go on. There is very little that you can do with water temperatures under 60 degrees.
Mike

Thanks Mike, unfortunately the temp is in the low 40's .. would I not cause even more stress if I had to try move him inside ?

Also wouldn't I need a recycled tank inside or with this temp there is not much I can do ?

I also don't have a tank in doors so would need to consider buying a stock tank or something.

I had a mature goldfish that had a big chunk of meat taken out of her side just after the anal fin by a heron this spring. It was so so deep that from up top her body was bent sideways at the wound. I figured she would die for sure. It healed and as the muscle grew back, she straightened out. She is fine now.

Rapidwiz,

With pond temps in the 40's there is very little healing going to take place on this fish. Yes it would cause more stress to move the fish but the warmer temps would allow the fish to heal if the water quality can be kept excellent. Outside the fish is going to have to go all winter and then the real problems begin. As the water starts to warm every little thing in the pond will be able to get to the bare meat. It is most likely that the fish in early spring will either get an infection or fungus will attack it. Depending on what condition the pond is in will determine how much of a chance the fish has.
Mike

I agree with Mike that the overall health and cleanliness of your pond will be a determining factor in the healing of your fish. If you are being conservative (as I have been in the past with injured fish with good success) then make sure your pond is in pristine condition. Nutrition is another factor. As soon as your fish are eating again make sure that they have optimal nutrition. In early spring you can feed a wheatgerm based food soaked in orange juice.

Why couldnt he bring it in to a tank & keep him there till spring then put him back to the pond ,that way you can treat it for sure.I would,I wouldnt chance losing it.But then Ive had aquariums ,ponds over 50 years.

I am a goldfish person but they are nearly the same fish. In my education on the subject for goldfish the first course of action is to salt the water. 1 tablespoon per gallon.

If it is imperative to bring it inside, as long as the temp change does not exceed 3 degrees per hour it should be fine. If you can grab lots of filter media to put into your new filter your temporary hold tank should cycle just fine. I would use some of your pond water as well, doesn't have to be a lot. Just check your water parameters once to twice a day to make sure there is no bumps. Do you have an API master test kit? An appropriatley sized stock tank or a 55-75 gallon aquarium would do fine, to my knowledge 50 gallons per koi is the general rule of thumb.

You can moderate the temperature rise by adding cooler water or ice until you can get the tank to room temperature.

Here is a link that might be useful: A forum for goldfish and koi

On that site I sent you there is an emergency 911 area that you can post to, I had to make sure this was for koi too as koi has its own forum but no 911, but the 911 I found out is for both.