Shonisaurus...?

[Garlyle]

There's several good foods you can use as a fisher. The three best, in ascending power (and ascending price due to being harder recipies/requiring rarer materials):
Trapper's Quiche (+17 Gathering/+7 Perception on HQ)
Tomato Pie (+19 Gathering/+8 Perception on HQ)
Spinach Quiche (+24 Gathering/+10 Perception on HQ)

With Spinach Quiche, you actually have the stats to catch basically everything in the game short of Nepto Dragon and maybe one or two other legendary fish (Which you would definitely be able to catch with the FC buff active)

I haven't heard anything about needing Perception to catch Shonisaurus (or any fish really, barring increasing your HQ chances for those who are mooched). Or necessary for any particular fish. HQ Stuffed Artichoke would get you to 381 Gathering/320 Perception.