Los Angeles, California - The warming of the ocean's surface is forcing anchovies and sardines – a key source of food for dolphins and whales – into deeper and colder waters further off the coast.
On a boat off the coast of California, Sara Lesser gazes wistfully at dozens of dolphins playing in the vessel's wake. This summer, extreme heat is making such a scene increasingly rare.
On daily tourist boat trips, "the number of whales and dolphins we're seeing is less than we would on a normal year," Lesser, a 39-year-old naturalist at the Aquarium of the Pacific in Long Beach, told the AFP.
Dolphins and whales "are going to follow their food, and so we're seeing less sightings" due to reduced anchovy and sardine stocks, Lesser explained.
The educator aims to raise awareness among visitors about the plight of the animals, as fewer whale sightings is just a harbinger of larger negative changes.
Surface water temperatures along the California coast are now around three–four degrees Celsius above normal levels, the US National Oceanic and Atmospheric Administration (NOAA) reports.
The current heatwave has been ongoing for "about six months," said Andrew Leising, a research oceanographer at NOAA.
What makes it more worrying is that it coincides with the return of El Nino. This year, scientists are predicting that El Nino could rank among the largest ever recorded.
"Chances are this El Nino is going to be stronger than the 2015–2016 one," Leising said, noting the devastation wreaked by the last heatwave.
Ocean waters became so hot a decade ago that thousands of birds died because they could not reliably get fish on the surface. The carcasses of malnourished sea lions and whales washed up on beaches.
This year, conditions are likely due to be worse – dozens of pelicans and cormorants have already been found dead near San Diego.