I just got my Eternium Line the last Extravaganza, which was the last thing I needed to max out my fishing skill :D. It's now, with only gear and base skill, 502. I think this is the max that can be achieved with current available gear.
To get it I have equipped:
- Arcanite Fishing Pole (+35)
----> Eternium Line (+5)
- Lucky Fishing Hat (+5)
- Nat Pagle's Extreme Anglin' Boots (+5)
- Gloves Enchanted (+2)
+ 450 Base Skill.
If you count in buffs, you can get to a max of 662:
- Underbelly Elixer -> Tuskarr (+50)
- Captain Rumsey's Lager (+10)
- One of the best lures (+100)