The Indian Ocean Dipole (IOD) — a climate pattern that describes the difference in sea surface temperature between the western and eastern Indian Ocean — has turned negative in May 2025 for the first time since 2022. A negative IOD means warmer-than-average water in the eastern Indian Ocean and cooler-than-average water in the western Indian Ocean. For anglers fishing the East African and South African coasts, this shift has direct and significant implications.
Impact on South African Fishing
A negative IOD typically strengthens the Agulhas Current along the South African east coast, bringing warmer water closer to shore than average. For KZN fishing, this means the prime sailfish and marlin grounds may be accessible closer to shore this season — reducing run times and fuel costs. The warmer inshore water will also likely accelerate the usual seasonal patterns, with peak couta and garrick fishing potentially arriving 2–4 weeks earlier than the historical average.
Impact on Mozambique
The Mozambique Channel is already running 0.6°C warmer than average on the western side. This is concentrated baitfish activity — warmer channel water means more sardine and mackerel feeding on elevated plankton levels, which translates directly to more marlin and sailfish in the channel. Early season reports from Bazaruto and Pemba are already reflecting this with above-average catches of sailfish reported from October onward.