ocean trade; maritime trade
Refers to commercial trade conducted across oceans, typically involving long-distance shipping.
Ocean trade is important for the country's economy.
This port developed as a hub for maritime trade.
貿易 is general 'trade' (often international), while 遠洋貿易 specifically refers to trade over long ocean distances.
海上貿易 also means 'maritime trade' but can include coastal or short-sea shipping, whereas 遠洋貿易 emphasizes deep-ocean, long-distance routes.
Compound of 遠洋 (open sea, ocean) and 貿易 (trade, commerce).