Assuming that the fish is properly drawn using closed paths, you could try giving it a white stroke aligned to outside.
Or else, make a copy of the fish, colour it white with a white stroke and poke the copy behind the original fish.
Assuming that the fish is properly drawn using closed paths, you could try giving it a white stroke aligned to outside.
Or else, make a copy of the fish, colour it white with a white stroke and poke the copy behind the original fish.