The princes of the sea are not the kings of the isles, but the merchant-princes of the city (Isaiah 23:8). They shall lay aside their robes of state—Tyrian purple embroidered with gold and silver—and shall put on the garments of mourners.
Jonah 3:6 presents an interesting parallel. The word thrones is used, as in 1 Samuel 4:13, for any chair of state, as that of priest or judge (Proverbs 9:14; Esther 3:1), as well as for the specifically kingly throne.
For the, most part, however, the later meaning is dominant.