Jawfish are species of saltwater fish very similar in appearance to blennies. They are however smaller in size than blennies and are characterized by their comparatively larger mouths and heads. Jawfish are an extremely intelligent, hardy species of fish and are highly popular amongst beginner and experienced aquarists alike. Jawfish are species of saltwater fish very similar in appearance to blennies. Most species of jawfish have dazzling body colorations and patterns. They come in shades of pastel, yellow, blue, green, brown, black and white.