There was no "fish god dagon.". Dagon was an agricultural deity associated with the grain harvest. Just one of about 200 things Alexander Hislop got wrong.
>>There was no “fish god dagon.”.<<
I suppose the fact that from the waist down he was a fish doesnt count for anything right?
http://www.bible-history.com/sketches/ancient/dagon.html
Dagon was the god of the Philistines. This image shows that the idol was represented in the combination of both man and fish. The name “Dagon” is derived from “dag” which means “fish.”
Although there was a deep affection from Dagon’s worshippers to their deity, the symbol of a fish in human form was really meant to represent fertility and the vivifying powers of nature and reproduction.
Note the hat of the priest to dagon. Then you may want to search scripture for references to dagon.