where and how do i fish rocktails?

 

do i need 2 do a quest?

You need level 90 fishing to catch the fish and level 93 cooking to cook it.

You use a fishing rod and for the bait you use Living Rock Remains, which are obtained from mining the remains of one of the rock creatures after you kill it and you need level 73 mining to mine it.

 

As to where you fish them, you fish them in the Living Rock Caverns