Pygmy Suckerfish are primarily caught from the schools of fish found in Northrend but have a smaller chance to be found in open water. Schools of fish, with the exception of Crystalsong Forest have about a 65% chance to drop suckerfish, while open water has about a 10% chance. Note that the suckerfish is an adittional catch to the fish you catch from the school or body of water, you will never catch a pygmy suckerfish alone.
The droprate should remain as 10% on Open Sea, and change from 10% to ~75% on schools of fishes
The item Pygmy Suckerfish have atm a droprate of 10% everywhere (schools and open sea)
Open Sea
Schools
But it should be arround 75% on schools after patch 3.0.8 and 10% on open sea.
Link
Previous information
The droprate should remain as 10% on Open Sea, and change from 10% to ~75% on schools of fishes