Generally the only fish you DON'T want to feed fresh is Pacific Northwest Fish, you could be safe and freeze it for 2 weeks but I personally would feed it fresh from around there.

 

I'd feed it!

 

Yup!!

I'd freeze it for a few weeks first and check it out for hooks beforehand. Did you catch it yourself?

 

My husband caught two trophy size and filleted them, but there is still tons of meat plus the head (probably 3-4 lbs each) left after he cut the good stuff off for us. My GSMD has only eaten canned fish so I thought I'd give this a try but wasn't sure it was safe for her to eat. Free raw meat isn't something we come across very often! Thanks for all the responses. We will give it a whirl tomorrow and see how it goes! Oh...no hooks. He checked first!

 

There are a couple other cautions with fish. Mercury is a biggie. Your fish probably have more than is safe to feed in goodly amounts often. I put Max's weight in the calculator and feeding one whole meal a week wouldn't be a good idea for him. I probably would go ahead and use it, just not as the omega 3 source for a whole week.
Sea Turtle Restoration Project : Got Mercury?

I am sure the fish is fresh and was handled properly so the problem with slightly overripe fish called scromboid poisoning isn't an issue, just be aware. The very slight overripeness can cause a severe allergic reaction and some fish are more likely to cause it than others.

If you fed only fish for an extended period of time you might cause beriberi. Some fish contain an enyzme that destroys thiamine. I figure sardines aren't exactly a natural food for dogs anyway so feed them but not on days he gets pork which has a lot of thiamine.