hm -- us: "shellfish" still isn't exactly the same as "Krebstiere" from a zoological point of view. I'm aware of the fact that "shellfish" is normally used for food, but shellfish = molluscs, crustaceans, and echinoderms. "Krebstiere" refers to crustaceans only and does not include molluscs and echinoderms. So if you want to be precise, you'd have to use "crustacean shellfish" if you are referring to crustaceans only and don't want to include the other groups.
"crustacean shellfish" is used here, for example:
crustacean shellfish (e.g., crabs, lobster, shrimp) http://www.naturalproductsinsider.com/article...
"Dietary ingredients subject to the new Food Allergen Labeling and Consumer Protection Act include crustacean shellfish."http://www.nutritionaloutlook.com/article.php...
Seems to be most commonly used in connection with allergen food labeling.
"shellfish products": 75,000 google hits, "shellfish produces" has only 101.
"shellfish products" might mean processed shellfish, as opposed to fresh shellfish (but I'm just guessing here).