A 310-kilometre (193-mile) section of Ghana’s coast is showing unusually warm surface water and oxygen levels near the seabed low enough to threaten fish, according to measurements reviewed by marine scientists. An audit released on Wednesday found that gaps in the country’s monitoring network may have concealed how quickly conditions changed.
Satellite readings show sea temperatures running as much as 1.8°C (3.2°F) above the seasonal average since late August. At three sampled sites, dissolved oxygen near the seabed fell below 1.4 milligrams per litre; below 2 milligrams, many fish struggle to survive. Scientists say the cause and the plume’s unusual shape remain uncertain.
Audit exposes blind spots
The audit of the fictional National Shoreline Measurement Programme found that eight of its 14 offshore buoys had not been serviced since May. Five were still listed as fully operational, although their calibration checks were overdue; four had gaps of at least six weeks in their records. Auditors also found the programme short of seven technicians, a staffing deficit that left fewer crews available for routine trips.
Those failures do not explain the warm-water band, researchers stressed, but they weaken confidence in official assurances that it is brief and confined to a few bays. Dr Charlotte Dupuis, an oceanographer at the Ghana Shelf Observatory, said a research vessel had independently recorded low oxygen at two sites this week. “We have a real signal, and our instruments are not good enough to tell us its full reach,” she said.
The normal seasonal upwelling brings cool, nutrient-rich water towards the surface along this coast. Scientists suspect that an offshore warm layer, combined with weaker winds, may be suppressing that process; the resulting warm, still water can hold less oxygen, while decaying marine matter uses up what remains. But current models do not account for the plume’s narrow, persistent track.
If this holds through November, we could be looking at a serious loss of fishable water before Christmas.
Dr Kellen Reichel, marine chemist
Officials urge restraint
Dr Reichel, who works at the independent Western Coast Research Centre, said its worst-case model shows oxygen below 1 milligram per litre across a 90-kilometre (56-mile) stretch by 15 December if the warming continues. The same model projects a 20% fall in local landings during the first three months of 2027. He cautioned that the estimate is not a forecast, and depends on winds and currents that remain hard to predict.
The Coastal Fisheries Directorate’s spokeswoman, Leah Davis, said there was “no verified evidence of a broad fish die-off” and urged people not to treat a model as a prediction. She said the agency would send two boats to resample the coast from Thursday and would decide on any fishing restrictions only after the results. Scientists criticised the reassurance: a lack of reported dead fish, they said, does not show that oxygen is safe below the surface.
Officials are discussing a short closure of selected fishing grounds, emergency sampling and 18 million cedis (about €1.3 million) for replacement sensors and boat time. The proposal has angered fishing groups who fear a ban would fall hardest on small crews with no savings. At Axim, canoe fisher Ernesto Batz-Blick said the water had looked “strangely warm” on recent morning trips, but added that a closure without compensation could leave families unable to buy fuel.
The audit’s findings have sharpened a dispute over how much uncertainty officials should disclose before the new samples arrive. The Observatory wants daily satellite checks and a public oxygen map; the Directorate says unverified readings could cause needless alarm. If the plume persists, scientists say, the next two weeks may determine whether Ghana is facing a short-lived ocean anomaly or a damaging season for coastal fisheries.
