Easy, the scientific method does not apply to evolution.
There are many scientific methods and most of them are used to substantiate the Theory of biological evolution. In all cases peer review is used, which is probably the "method" you think means nothing.
Fish are in the path of common descent from unicellular organisms to man. We had a common ancestor, but probably split off from each other millions of years ago.
Many people you know look like fish, many smell like fish and some are almost as smart as fish. I wouldn't put down fish too much, if I were you. lol
Well said.