From what I understand, fashion marketing is more about identifying the needs and wants of a consumer group, and then creating the product that fills this. It’s a lot about data collection, watching trends and trend-setters and then promoting back to the public what they have already told you. In fact if you communicate the exact same message that you’ve been given by the public, back to them, you get a lot of agreement from them that the product is what they want.
Merchandising is then taking the completed product the last step of the way. The retail chains and sales-people now have the product, and need to vamp-up awareness of it in more local customer bases to generate the sales.
I started working out this difference after reading the article at http://tprog.com