First, I am sorry to hear this, Ken.
Second, a pond load of big fish could be quite valuable. If I were you, I would strongly consider getting professional evaluations of everything valuable on the property to ensure you get fair compensation for all of it. It might be worth a professional electrofish sampling to put a dollar value on the fish in the pond; certainly worth talking with a pro like Grimes, Lusk, etc. and telling what you know of the size and numbers of fish in the pond, getting a very rough estimate of their value, and making the decision whether or not to electrofish and get a hard dollar value to use for compensation purposes.
We got a professional, retroactive evaluation of what the timber value on our property had been at the time of acquisition when we had our place logged a few years ago. The result was quite valuable from a tax perspective, and if the IRS will follow a forester's professional estimate, you should be able to get as much value out of a professional fish squeezer's evaluation on your fish value.