I cannot see a dead fish as a "conservation success". Bluefin tuna are still rare - they only avoid being technically endangered cos they stabilised at a tiny number. That's not a healthy population, just a stable one. Let them breed and really do well before you fish for them if you have to.
First bluefin tunas caught off Yorkshire since 1960s ‘success story’ for marine conservation
Researchers laud return of giant tuna to North Sea after being fished almost to point of extinction
theguardian.com