There are two ways to verify a supplier of imported fish / fishery (a.k.a. seafood) products from another country:
The importer obtains the product from a country that has an active memorandum of understanding (MOU) with the FDA that documents the equivalency of their food safety systems, or
The importer implements verification procedures for ensuring the fishery products being importer were processed in accordance with FDA seafood requirements.
Memorandum of Understanding:
An importer can check if there is a MOU with the exporting country looking it up on the FDA website, here. Note that MOUs are not particularly common.
Verification Requirements for Importing Fish / Fishery Products
If you are unable to obtain the fish / fishery products from a country that has an active MOU, then you must conduct your own verification to confirm that the product was produced in compliance with FDA regulations. This verification may be completed by a competent 3rd party.
The importer's verification process must be written and must include the following, at minimum:
Product specs for each imported product that ensure that product is not adulterated.
One or more of the following:
HACCP and sanitation monitoring records that relate to the specific lot of fish being imported.
A lot-by-lot or continuing certificate from a government authority or 3rd party certifying that the food was processed in accordance with FDA regulation on fish / fishery products (21 CFR §123)
Regularly inspecting the foreign processor's facilities to ensure that the imported product is being processed according to FDA regulation.
Maintaining on file a copy of the foreign processors HACCP plan and a written guarantee (English) that the imported product is being processed according to FDA regulation.
Periodically testing the imported products and maintaining on file a written guarantee (English) that the imported product is being processed according to FDA regulation.
Another equivalent method of verification.
All verification records must be kept on file by the importer.