http://www.councilofexmuslims.com/index ... ;topicseenThe reference to the resurrected fish is derived from the Syriac Alexander legends, which in turn are derived from the story of Gilgamesh searching for the waters of immortality. Tesei talks about it here.
http://www.almuslih.org/Library/Tesei,% ... iquity.pdf
In the Alexander legends, his cook takes a dead fish and searches for the waters of immortality by putting it in water from various springs/rivers. When the fish comes alive and escapes, then he has found the waters of immortality.
The fish is not itself a symbol of Christ, although in Syriac theology Christ makes man immortal by distributing the "Medicine of Life," the Syriac phrase for the Eucharist, bringing them into paradise. So the idea of a river flowing from paradise (the land of Christ) that carries immortality with it is very much a background of how Syriac Christianity envisioned the world, and which the Qur'an inherits.
What is significant about the Qur'anic version is that Alexander has been quite deliberately replaced with Moses. And this is very typical of quranic typology, which takes older Christian typology and deliberately renders it in pre-Christian form centered on Moses.
What characters have been replaced by others in the New Testament?