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What the Ocean Knows Six Months Ahead of the Fish
For decades El Niño has told this coast where its fish would be. A new review expects that signal to fade.
Between January and March the wind on the Mauritanian and Senegalese coast blows along the shore and toward the equator, pushing the surface water out to sea and drawing colder water up from below to take its place. That colder water carries the nutrients that feed the plankton, and the round sardinella that works its way up and down this coast every year follows the food and the temperature it can tolerate, north past Cape Blanc and on into Saharan waters. Small pelagic fish are the main commercial fishery of the entire Canary Current system, with landings of around 450,000 tonnes a year in a region whose coastal economies are built on them.
In some winters a large part of the population stops short and gathers south of the cape instead. Jorge López-Parages and colleagues reproduced that interruption by coupling a model of the water to a model of its plankton and a third one of the fish themselves, and found more fish off Cape Blanc in winter and fewer along the Saharan coast above it. The currents off the cape are what does it, reorganised during El Niño so that they stop carrying the fish toward the water it will tolerate. The line worth a reader’s…
