Nonexistent.
I'm a 300 Artisan Fisherman, I'd know.
I use a +20 Big Iron Fishing Pole, +2 Fishing enchant on my gloves, +75 Bright Baubles for most fishing, and +100 Aquadynamic Fish Attractors if I'm after Stonescale Eel. This means I'm usually fishing at 300+97, with 300+122 at most.
Useful fish:
Deviate Fish - Lushwater Oasis, Barrens
Firefin Snapper - Wetlands, Menethil Harbor
Oily Blackmouth - Wetlands, Menethil Harbor
Stonescale Eel - Tanaris, Steamwheedle Port
Nightfin Snapper - Feralas, Verdantis River
Sunscale Salmon - Feralas, Verdantis River
Winter Squid - Tanaris, Steamwheedle Port