The fact that Chilean Sea Bass (a very large saltwater fish) and Striped Bass (commonly caught in a freshwater pond near you) could be mistaken for one another points to the heart of the problem.
Kitchen staff illiteracy.
Striped Bass is usually caught in the salt water in the Northeast. They do spawn in brackish estuaries and are often caught there but I am unaware that they are caught in fresh water ponds. They can grow to about 60 pounds.
You’re probably being kind in chalking it up to kitchen staff illiteracy rather than the restaurant’s buyer cutting corners.