What is "tidra"

Tidra is an offshore island long and wide. Roughly the size of Manhattan (13.4 miles (21.6 km) long and 2.3 miles (3.7 km) wide).
It is the largest island off the shore of Banc d' Arguin, Mauritania and is home to a community of Imraguen fishing tribe. The island is part of the Banc d'Arguin National Park.