Step 1: Understanding the Concept:
Under the United Nations Convention on the Law of the Sea (UNCLOS), maritime boundaries designate jurisdictional zones.
Highly mobile fish stocks frequently cross these political boundaries, requiring cooperative international management.
Step 2: Detailed Explanation:
Let us look at the legal definitions of transboundary fish stocks:
1. Shared Fish Stocks: Stocks that live within the Exclusive Economic Zones (EEZs) of two or more neighboring coastal states.
2. Straddling Fish Stocks: Fish stocks that migrate between, or are found in both, an EEZ and the adjacent high seas.
3. Highly Migratory Fish Stocks: Oceanic species (such as tunas) that cover vast distances across multiple EEZs and high seas.
Since the question specifies migration between an EEZ and the high seas, these are legally defined as straddling fish stocks.
Step 3: Final Answer:
Fish stocks occurring in both an EEZ and the high seas are called Straddling Fish Stocks.