Sorry i've been editing my last post constantly. Take a look again haha.
Edit: This article is about cat food, but had a lot of interesting information.
Some relevant excerpts:
"Ingredients are listed on a pet food label in order of pre-cooking weight."
"Chicken is obviously chicken meat; Chicken Meal is chicken meat with the moisture removed. Any meat contains a high amount of moisture, up to 70% moisture. Chicken Meal is chicken with the moisture removed and thus provides the dog or cat with more protein nutrition by weight."
Originally Posted by finnfinnfriend
but obviously most of the moisture is gone from the foods with whole fish too...??
Since the ingredients are listed pre-cooking, most of the moisture could be removed post-mixing.