Grass carps are a type of fish.
Like all types of fish, each grass carp gives one fish fillet when caught.
Catching grass carps
Grass carps can only be caught with green and purple lures in fishing spot #2 (the reedy area with some water lilies).
Grass carps can be caught in small circles and therefore are harder to catch.
See Fishing List for more detailed information.
Grass carps in the fishing book
The Grass carp is on page 14 of the fishing book:
This vegetarian fish leads a simple, healthy life. Tip: Does not like worms!