"Eh, if it's just symbolically bringing back a few dozen pounds of fish, it's not that much trouble. With the right handling, you don't need to pay any fees. Just provide proof of origin, and you can check it with your plane luggage. Then, after you enter the country, if you're not too unlucky, you won't need to spend a single cent more,"
"Not too unlucky?"
"Right, customs might still do a spot check. If they don't find anything, you're OK. If they do, it's just a matter of paying a small entry tariff based on the weight. With a proof of origin, it's not illegal; at worst, it's a small misstep because you weren't clear on the process the first time."
"So, if I do as you say, how can I maximize my benefits?"
"The easiest way is definitely to sell it to a company that specializes in Bluefin Tuna. Sign the contract, take the money, and then it's none of your business!"