Whale Shark

Photo: Simon Pierce · CC BY-NC

Whale sharks concentrate in Mafia Island's waters between October and February, when the East African monsoon reversal brings nutrient-rich currents past the island's western coast and triggers plankton blooms that attract aggregations of these filter-feeding giants. The Mafia aggregation is distinct from other East African aggregation sites in its proximity to the reef edge — whale sharks are frequently encountered at depth along Kinasi Wall rather than only at the surface, suggesting they are actively feeding on the concentrated zooplankton in the wall's upwelling zone. Tanzania Whale Shark Project researchers have documented over 200 individual whale sharks in Mafia waters through photo-ID, with some individuals returning across multiple consecutive seasons.