What protein are there in the fishes salmon, Tinned tuna fish, Plaice, Perch and Herring and why do they have?

Proteins may be structural - bones, muscle, etc. or they may be enzymatic, helping chemical reactions important to metabolism and life, or they may be signaling - coordinating the body's growth and maintenance, etc. There are probably thousands of different type of proteins in every species of fish and as many that they share in common.