Raw manta ray is a members-only fish that requires level 81 Fishing to obtain.
Like sea turtles and tiger sharks, manta rays may only be caught while playing the Fishing Trawlerminigame. It can be cooked at level 91, although there is a very high burn rate even up until level 99. This can explain why cooked manta rays are sometimes more expensive than raw ones.
The Ardougne Tasks require a manta ray to be fished on the trawler as part of the Elite tasks. Boosts can be used to achieve this.