Oyster Sauce vs. Fish Sauce?

[lgray104]

Are they interchangeable, or not so much? I'm making the following...
Honey-Gingered Pork Tenderloin
(or ‘the best thing ever’)
Keeping Up with the Joneses
kendallandkeith.blogspot.com

Ingredients:
2 (3/4-1 lb) pork tenderloins
1/4 cup honey
1/4 cup soy sauce
1/4 cup oyster sauce
2 Tbsp brown sugar
1 Tbsp, plus 1 tsp minced fresh ginger root (this must be fresh. must.)
1 Tbsp minced garlic
1 Tbsp ketchup
1/4 tsp onion powder
1/4 tsp ground red pepper
1/4 tsp ground cinnamon

[treedimensional]

They are very different. Fish sauce is watery and salty/pungent in flavor. Oyster sauce is thicker and a slightly sweet-salty. Tough to describe tastes, but they are not at all similar in flavor or texture.