Figure 1

Map of the study sites representing the sampling sectors along the Northern and Northeastern Brazil (1) indicating the 10, 50, 100 and 200 m isobaths. Detailed maps of the sampling regions: (2) Amazon Lowland (AL), (3) Northeastern coast (NC), on the coast of the Maranhão (MA) and Piauí (PI) states, and (4) Amazon Estuary and adjacent coastal zones (AE). Amapá (AP), Pará (PA), Maranhão (MA), Piauí (PI) and Ceará states (CE). Sector AE only includes the study sampling area and not the entire Northern region. Dots indicate the sampling locations.