I was just looking at the "Nature's Variety" website and they have an area called ingredient glossary where you can look up the different ingredients and learn more about it. This is what it said for herring meal:
Herring Meal
Herring meal is the clean, dried, ground tissue of undecomposed whole herring or herring cuttings. Herring are small oily fish much like sardines that inhabit shallow temperate waters in the Atlantic. They are sustainably caught and processed fresh. Our high-quality herring meal is an excellent source of Omega-3 fatty acids and is naturally preserved with mixed tocopherols.

This is great to know that their fish isn't preserved with ethoxyquin. I still haven't found this label on the bags of dry food though.


On the "Taste Of The Wild" website they also have an area where you can learn more about their ingredients.
Ocean Fish Meal:
A high quality source of protein and omega-3 fatty acids. The omega-3 fatty acids from marine sources, EPA and DHA, provide nutrition for optimal skin and coat health as well as excellent overall health.

It doesn't let us know what's it's preserved with.