Coastal communities in Senegal are reeling as stocks of sardinella – the country’s most consumed fish – disappear from local waters. While fishermen blame industrial trawlers, scientists say climate change is sending the small, paddle-shaped fish northwards in search of cooler habitats.
Fisherman Amadou Gueye returns to Dakar's small port of Ouakam with only five octopuses after a long day spent at sea.
"It's not good. There's the current and no fish," he laments. "The big boats make it hard, leaving us with nowhere to fish."
Finding sardinella, a staple food and crucial economic resource in Senegal, has become a major challenge, confirms Ibrahima Ndiaye, vice-president of Ouakam's local fishermen's committee.
"The pirogues now spend seven days at sea going to Mauritania, Guinea-Bissau and Guinea-Conakry – whereas in the past there was daily fishing," he tells RFI.
"We used to go out in the morning and come back in the evening."
Ecosystems changing
A study this month in the British journal Scientific Reports found that sardinella were migrating up the coast of west Africa from Senegal and Mauritania to Morocco, where large catches are now being recorded.
The so-called "tropicalisation of ecosystems" – or warmer sea temperatures altering north-west African coastal waters – is driving the redistribution of sardinella and other small pelagic fish.
The warming has caused sardinella to migrate northward at a rate of 181 kilometres per decade.
Led by scientists in Senegal, France, Norway, Morocco, Mauritania and the Gambia, the study analyses data from 2,363 trawlers and 170,000 kilometres of acoustic sea surveys done between 1995 and 2015.
It found that more than three decades of warming had impacted the cold ocean Canary Current that flows along the coast, regulating the marine ecosystem and influencing climate patterns.
Climate stressors
Already over-exploited fish stocks were being forced out of their usual habitats by a "complex interplay of climatic-related stressors", the report warned.
These included changes to wind patterns and "upwelling" – when nutrient-rich, colder waters from the bottom of the ocean rise to the surface to support marine life.
"While overfishing is obviously a direct human activity, the powerful environmental impacts are an indirect human activity," Vincent Rossi, an oceanographer with the French research centre CNRS, told RFI.
The loss of sardinella, a vital resource, risked further threatening food security in West African countries that depend on the fish, the study found.
It warned that shared stocks would become increasingly difficult to manage sustainably.
The researchers said better monitoring was needed to properly understand the ways in which the marine ecosystem off north-west Africa was responding to climate change.
This story is partly adapted from a report by RFI's Dakar correspondent Léa-Lisa Westerhoff.
