Use 0303310015 when a single shipment contains both Atlantic and Pacific halibut that are not segregated by species at the line level. If the shipment is entirely Pacific halibut with clear documentation, 0303310020 is the correct line; if entirely Atlantic halibut, use 0303310010. Mixing species without segregation defaults to the combined line. A licensed customs broker can help determine the appropriate classification based on your shipping documentation.

Acceptable documentation typically includes a catch certificate or vessel log identifying the species by scientific name, a processor's certificate of species identity, and country-of-origin documentation. For Canadian-origin halibut, IPHC landing records can serve as supporting evidence. FDA may also request HACCP records from the foreign processor as part of its seafood import oversight.