Most product taxonomies will categorize them separately. Here's two examples trying to categorize tilapia.

Google Product Taxonomy:

Food, Beverages, & Tobacco > Food Items > Meat, Seafood & Eggs

Note the distinction between meat and seafood.

GPC:

Food/Beverage/Tobacco > Fish - Prepared/Processed (Frozen) > Attribute: Type of Fish = Tilapia

Whereas meat in the GPC is defined separately:

Food/Beverage/Tobacco > Meat/Poultry/Other animals - Prepared/processed> ...

Your local grocery store probably is organized the same way. Many people think of fish flesh and meat as being different things. Words are made up and all categories are artificial, whatcha gunnuh do.