You might want to be clearer. A pescetarian would be someone who only eats fish, and I'm going to assume you eat other things as well. I assume you mean to say you're mostly vegetarian but do eat fish as the one animal food you'll consume. Is this true? If so, fish is an excellent protein, as are beans on the vegetarian side, so you shouldn't be having a problem getting enough protein. Is there more?
Hello,
Fish is high in proteins. You can get high quality protein from eggs, legumes, cheese, nuts, soy products, etc. Get a diet chart made from a nutritionist. Do keep me posted.
Best luck and regards!