This topic has been around in a few variations, but a "future problem" has become a "current problem", at least for me, now.
I have done it. I hit rank 49 in fishing. Fishing is a dead end currently.
tl;dr: Fishing becomes incredibly painful at high levels.Funny enough that my "sc competitor" is also at rank 48, because at 49, the pain begins.
Fishing works in the following way: every 5 ranks you gain +1 fish tier.
So at the following ranks, you get the following tiers:
Code
0: 1
4: 1 2
9: 1 2 3
14: 1 2 3 4
19: 1 2 3 4 5
24: 1 2 3 4 5 6
29: 1 2 3 4 5 6 7
34: 1 2 3 4 5 6 7 8
39: 1 2 3 4 5 6 7 8 9
44: 1 2 3 4 5 6 7 8 9 10
49: 1 2 3 4 5 6 7 8 9 10 11
54: 1 2 3 4 5 6 7 8 9 10 11 12
59: 1 2 3 4 5 6 7 8 9 10 11 12 13
64: 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Every 15 fish levels / ranks, you are able to cut off 1 tier if you fish in a well, meaning that if you manage to find a well, and don't 1006 on it, you're getting the fish as follows:
Code
0: 1
4: 1 2
9: 1 2 3
14: 2 3 4
19: 2 3 4 5
24: 2 3 4 5 6
29: 3 4 5 6 7
34: 3 4 5 6 7 8
39: 3 4 5 6 7 8 9
44: 4 5 6 7 8 9 10
49: 4 5 6 7 8 9 10 11
54: 4 5 6 7 8 9 10 11 12
59: 5 6 7 8 9 10 11 12 13
64: 5 6 7 8 9 10 11 12 13 14
Every fish you find can spawn in a mana, life or rare variation. If we fully ignore rare fishes and assume 0% stacking (meaning you stack all fish, regardless of how good they are), you cannot keep stacking after rank 49, because you get more fish than you have slots.
You get 8 tiers in a well at rank 49 (because the cutoff of tiers just does not... cut it anymore), and you have 16 inventory slots. You still need 1 free slot to get new fish, and 1 free slot for your rod, meaning carrying 7 tiers is the maximum.
I have posted this image for visualization before:

Further pain points:
- You have to cancel 50+% of your fish because you cannot catch it (or it randomly escapes).
- You don't get prof for canceling, unlike suffusencing and cooking.
- You need good rods (100+ dura), because otherwise fishing is even worse. It has gotten to the point where I can't even fish without an event of 60+% anymore.
- Those rods frequently keep losing durability due to lag or 1006s. Yes, there was a safeguard implemented, but that doesn't work 50+% of the time. At least we're only losing dura, not the rod now.
- You get less prof per fish(!!) than someone at a lower rank does. So you need more prof, fail more fish, and need to overall catch more fish in order to rank up. Just some quick maths: I am getting roughly 61% of the prof that someone at rank 15 does. Combine that with half the catch rate, and I need 3.22x the amount of fish (attempts) somebody at rank 15 needs, for the same amount of prof, not for a rankup
- At rank 49, even in a well, about 70+% of your fish is not usable to obtain cooking prof (my fishing and cooking rank are about 10 ranks apart)
- You cannot even fish for lower fish and create a few low stacks "quickly". It just doesn't work, level 1 fishes are as difficult as level 50 fishes, and provide the same loot, but no prof
- At lower ranks, you can use the % minimum stacking, and stack the crappy fish (falling below your %) to keep for cooking prof later. At high rank you can't, because you don't have slots.
But of course, this would just be a complaint topic if I didn't provide any solution approaches:
- Make each 5 ranks (of each skill?) increase your item slots by +1
- Apply full or partial extra equipment slots to item slots
- Allow unstacking of items, so that life and mana fish could go to the same stack und unstacked later
- Cut off a tier every 5 ranks in a well, not every 15 ranks. Every 10 ranks almost works, until 64, where you're short 2 slots again. This would also tremendously help with cooking prof.
I have mentioned these various times, sometimes even tagging paul, but I haven't even received a response whether any of this is even intended behavior.