You should know the old saying "Give a man, a fish and he eats for a day. Teach a man to fish and he'll eat for life". Well the same is true with the RPG fishing, however these fish will also give you stamina.
As of April 2019, there are four types of fish you can catch with the command [nya!rpg fish]. As of the March 2020 update, two new fish where added.
These fish are :
As of August 2019, you are now able to buy Raw Fish, Raw Carp and Raw Mackerel from the RPG shop under the Food icon. You are unable to buy Raw Prawn or Raw Oysters from the shop, right now.
You can also get the message that you have caught nothing.