These are a great way to get food for people who dont want to pay for it. The fish can drop 2 or 3 at a time, plus scales which are good for druids and such, plus swimming. Though sense they have no value but to a vendor and as food, its kind of a bad idea to farm unless you plan to use them yourself.
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Stupid People bother me.... QUIET YOU!!! YOU DONT GET AN OPINION!!!
I used to hunt these as a source of exp as a halfling newbie... Good food loot, Easy kills, and you raise your swimming all at once, kill the piranha's as they spawn, and get yourself the rantho rapier by turning in their teeth to the guy in top of the bank, you'll get a real fast 2h slash to help train up the skill. I highly suggets it for newbie rangers, warriors, and pallys.