Traceability requires that every participant in a supply chain can identify the same product, location, and event in the same way. Without a shared identifier system, a processor's lot number and a retailer's SKU are just internal codes that mean nothing to each other.
GS1 solves this with globally unique, publicly resolvable identifiers. A GTIN assigned to a halibut fillet SKU is the same number whether you're reading it in Kodiak, Tokyo, or a London grocery. A GLN assigned to a processing facility uniquely identifies that location in any GDST-compliant system.
GDST — the seafood industry's data standard — uses GS1 identifiers as its foundation. Implementing GDST means implementing GS1. They are complementary, not competing standards.