The canal crab is a critter that is the objective of the cooking quest 
[10 Daily] Feeling Crabby?, given by Lua error in package.lua at line 80: module 'Module:Factiongfx/faction_tip_link.json' not found. Robby Flay near the Stockades in the Mage Quarter of Stormwind City. while on the quest, you will be able to loot these crabs, but if not on the quest, you will kill them. They are still killable while on the quest, but once killed, you cannot loot it.
Patch changes[]
- Lua error in package.lua at line 80: module 'Module:Inlinegfx/img_link_data.json' not found./Lua error in package.lua at line 80: module 'Module:Inlinegfx/img_link_data.json' not found. Patch 4.0.1 (12-Oct-2010): Added.