Have you talked to a income tax specialist CPA about this? I'm no tax expert, but I took several tax classes and I'm doubtful that the write-off would hold up if you got audited. The goodwill donated write-off is a different scenario because a person buys the goods for full retail, then later writes off the donation at current market values, which is obviously much less.
With donated tuna, I guessing that the write-off could only amount to the lesser of:
- the wholesale value of the tuna; or,
- the expenses associated with catching the tuna (gas, bait, tackle, etc.)
I would ask a CPA if an individual taxpayer could write off recreationally caught donated tuna. I am sure that a commercial fisher with some type of business entity could write off donated tuna, but I don't know about someone who catches fish for fun and doesn't expect any monetary benefits.
Even though the expenses most likely are always higher than the wholesale value of the tuna, a person would need to hold on to all receipts from the trip and keep detailed records to prove that the wholesale price was less than the boat expenses. Not worth the effort IMO.