Genetic engineering is accomplished in three basic steps. These are (1.) The isolation of DNA fragments from a donor organism; (2.) The insertion of an isolated donor DNA fragment into a vector genome and (3.) The growth of a recombinant vector in an appropriate host.
When you do that the fish will die. That is because it will take too much water in it and die from it, or rather, the fish's cells will take too much water in.
