Pandarian Angler

Emperor Salmon and Krasarang Paddlefish pools I found along the river between Valley of the Four Winds and Krasarang Wilds.
Giant Mantis Shrimp pools I found easily along the east and south coasts of The Jade Forest.
Jade Lungfish pools I found in the rivers and lakes of The Jade Forest, and also fished up in open waters or rivers.
Redbelly Mandarin pools I found in The Jade Forest, and also in the river between The Jade Forest and Valley of the Four Winds.
Golden Carp are the most common fish and can be fished from any rivers or lakes in Pandaria.
Jewel Danio pools now found in the lakes of the Timeless Isle (thanks to Ipm555 for the reminder).
Reef Octopus pools I found among the islands off the east coast of The Jade Forest.
Tiger Gourami pools can be found in Kun-Lai Summit (thanks to Keekyo for pointing that out) and in The Veiled Stair (thanks to digitalutopia1)
Mimic Octopus, Flying Tiger Gourami and Spinefish Alpha are fished up from any waters in zones that contain both fresh and seawater areas, namely The Jade Forest, Krasarang Wilds and Valley of the Four Winds.
They begin a quest that leads you to Nat Pagle

If anyone has updates or good places to find the fish let me know and I'll update.
Happy fishing!

Mimic Octopus, Flying Tiger Gourami, and Spinefish Alpha are semi-rare fish that can be caught in both open water and pools.

Mimic Octopus is caught in the ocean.
Spinefish Alpha is caught anywhere that Spinefish are caught, which is inland water in Sha-touched lands (e.g. Kun-lai Summit).
Flying Tiger Gourami is caught in inland water where Spinefish are NOT caught. However, some areas in Krasarang Wilds are exempt due to being objectives of quests. Check the wowhead maps or El's Extreme Anglin' for specifics or fish in another zone.

These fish are unique, so you can only carry one at a time though this is only important if you're farming Nat Pagle rep.

You get credit for this achievement not only from fishing but through purchasing a bag of the needed fish from the cooking vendor at Halfhill [npc=64395].