Copied from GameFAQs, so take it as you will. Seems pretty trustworthy judging by the above anecdote with Run Speed Up, lol.
Firefin - 5x chance for Ink Saver (Sub), 1/2 chance for Ink Recovery Up
Forge - 5x chance for Special Duration Up, 1/2 chance for Ink Saver (Sub)
Inkline - 5x Defense Up, 1/2 Damage Up
Krak-On - 5x Swim Speed Up, 1/2 Defense Up
Rockenberg - 5x Run Speed Up, 1/2 Swim Speed Up
Skalop - 5x Quick Respawn, 1/2 Special Saver
Splash Mob - 5x Ink Saver (Main), 1/2 Run Speed Up
Squidforce - 5x Damage Up, 1/2 Ink Saver Main
Takoroka - 5x Special Charge Up, 1/2 Special Duration Up
Tentatek - 5x Ink Recovery Up, 1/2 Quick Super Jump
Zekko - 5x Special Saver, 1/2 Special Charge Up
Zink - 5x Quick Super Jump, 1/2 Quick Respawn
Link:
http://www.gamefaqs.com/boards/805617-splatoon/71923500 (The post's source for this info is the strategy guide.)