The Safavids, sidelining Manama, designated the nearby town of Bilad Al Qadeem as the provincial capital. The town was also the seat of the Persian governor and the Shaikh al-Islam of the islands. The position of Shaikh al-Islam lay under the jurisdiction of the central Safavid government and as such, candidates were carefully vetted by the Isfahan courts. During the Safavid era, the islands continued to be a centre for Twelver Shi'ism scholarship, producing clerics for use in mainland Persia. Additionally, the rich agricultural northern region of Bahrain continued to flourish due to an abundance of date palm farms and orchards. The Portuguese traveler Pedro Teixeira commented on the extensive cultivation of crops like barley and wheat. The opening of Persian markets to Bahraini exports, especially pearls, boosted the islands' export economy. The yearly income of exported Bahraini pearls was 600,000 ducats, collected by around 2,000 pearling dhows. Another factor that contributed to Bahrain's agricultural wealth was the migration of Shia cultivators from Ottoman-occupied Qatif and al-Hasa, fearing religious persecution, in 1537. Sometime after 1736, Nader Shah constructed a fort on the southern outskirts of Manama (likely the Diwan Fort).