Oh yes, you can give shrimps. Not too much too often, but as a treat, definitely.
Fish is ok as food, but not too much too often, especielly not raw fish.
If you by any reason give them much raw fish, say, tuna, try to give extra E-vitamine.
Cooked fish is more leeway in there.
Some cats are allergic to fish, or rather, if you happen to have a cat who seems to be allergic to something, and you are looking for the causes, begin with replacing the fish.
But for most cats fish is oK, and some few cats even manage to live solely on fish.
Almost all cats are also loving fish and fish smell.