In 1469 Shetland came under nominal Scottish control , although the Norse ' Lairds of Norway ' kept their Papa Stour estates until the 17th century . In the 16th century merchants from Bremen and Hamburg were operating a summer trading booth to buy fish from the local fleet . By the 18th century , two Scottish lairds , Thomas Gifford of Busta , and Arthur Nicolson of Lerwick , owned the island . They maintained a prosperous Haaf ( Old Norse : ' deep sea ' ) fishing industry , undertaken in the summer months using six @-@ oared boats known as sixareens .