You have to catch 100 of a specific species of fish to reach "class 10" in fish caught for that species. Then deliver 10 of a certain color of that species to to earn the "hunter of the [specific color]" (Grade 1) to be able to mount that type of fish on a WOODEN plaque. To get a golden plaque (the best one) you would have to catch 1000 of that species of fish! (and 50 of the specific color)
Recently I spent hours farming pondies reliably in a ghost fort in order to get my wooden plaque for a variety of those fish. 100 pondies caught over a number of hours (impossible if it wasn't pondies which spawn reliably and are caught quickly). Forget working towards anything other than the wooden plaque for a certain fish because the time investment asked of you is just way too much.
Moving on from pondies, it would be absolutely insane to catch 100 of any other specific type of fish for their wood trophy.. let alone hundreds more for the later tier trophy plaques. For fish that are hard to spawn in the first place, where it could take hours between sightings, how would you ever reliably catch even 100 of those type of fish... let alone 1000. For example, by sailing over to the devils roar and casting your baited line for devilfish you only really see one for every 10 or so fish that come nibbling. **If you are sitting there, actviely removing your rod from the water anytime it isn't the fish you are looking for it could take a good 10 minutes before you see ONE of the species of fish you are looking for (let alone the specific color of which you would also need an unreasonable number of)
As it stands, most players will never even get a WOODEN fish plaque for ANY type of fish in their entire time playing sea of thieves, even if they are interested. 100 fish MINIMUM before you are awarded a trophy for fishing seems completely out of touch. Initially I thought it was 10 of a specific breed and color of fish for a wooden plaque of it, 10 more for a better plaque, etc. Instead you have to farm hundreds and thousands of randomly spawned fish for potentially hundreds of hours to be able to mount the ONE that you want.
Im surprised there isn't more of an uproar about this! The requirements for a LOT of the trophys are really ridiculous, but fishing is the most disheartening in my opinion.