Which impact on South American fisheries results when El Niño-Southern Oscillation (ENSO) reduces coastal upwelling?

💡 Explanation

When ENSO reduces coastal upwelling off South America, nutrient supply to surface waters decreases because cold, nutrient-rich waters are not drawn up from the deep, inhibiting phytoplankton growth and disrupting the food web. Therefore, a decline in commercially valuable fish populations results, rather than species shifts or productivity increases which require nutrient abundance.

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