Research conducted by experts that conclusively show that fish do in fact feel pain, stress and anxiety just like any other vertebrae like your cats and dogs or even other primates. In fact Dr. Donald Broom Professor of Animal Welfare and advisor to the British government has said “The scientific literature is quite clear. Anatomically, physiologically and biologically, the pain system in fish is virtually the same as in birds and mammals. 
Fish are slippery little animals, that live in water, fresh OR salt.
On September 11 2015 (The fourteenth anniversary of 9/11) an article was published talking about National Lobster Day.
With fish farm enclosures packing the creatures in, well, like sardines, leaving little room for the fish to swim freely or to engage in their normal behavioral patterns. The result? Stressed fish, who like us, tend to get sick more easily when their defenses are down. With their immune systems compromised, the fish become more prone to illness, parasitic infections and diseases, which then can spread quickly through their over-populated aquatic quarters.