What does Isaiah 23:6 mean?

Through this passage Isaiah reveals how the destruction of Tyre will be felt everywhere. Neighbors who grew rich from all the revenue that flowed through its gates will mourn. Others also benefited from Tyre's shipping industry, including its trading partners around the world (Isaiah 23:1–5).

Now Isaiah calls for the people of Tarshish to join in the mourning. Tarshish is often identified with Tartessos on the coast of Spain. This city was all the way across the Mediterranean Sea from Tyre. The ships of Tarshish (Isaiah 23:1) were either built there or designed to make the long journey all the way across the sea. The city of Tarshish was said to be rich in silver, iron, tin, and lead (Ezekiel 27:12). The people of Tarshish would have benefited enormously from the trade conducted by the merchants of Tyre.