El Nino is bad news for salmon and steelhead

The little troublemaker is back.

It’s bad-but-expected news for salmon and steelhead runs up and down the West Coast, including those that return to the Snake and Columbia rivers.

The NOAA Climate Prediction Center said last week that El Niño conditions are now present off the coast of South America, and they can be expected to gather strength by this winter.

According to a news release from the agency, the weather phenomenon is identified by the accumulation of warmer-than-normal sea surface temperatures in the Pacific Ocean west of South America near the equator.

El Niño (little boy in Spanish) influences global weather patterns.

“Depending on its strength, El Niño can cause a range of impacts, such as increasing the risk of heavy rainfall and droughts in certain locations around the world,” said Michelle L’Heureux, climate scientist at the Climate Prediction Center, in the news release.

“Climate change can exacerbate or mitigate certain impacts related to El Niño. For example, El Niño could lead to new records for temperatures, particularly in areas that already experience above-average temperatures during El Niño.”

It also influences salmon survival.

El Niño brings warmer sea surface temperatures to the northern Pacific Ocean, an area where salmon and steelhead spend their time at sea.

That warm water depresses upwelling – the exchange of deeper, cooler water with surface water – and pulls aquatic creatures from the south, both predator and prey, with it.

Ocean water off the continental shelf that normally is dominated with northern copepods – fat-laden creatures near the bottom of the food chain – are replaced with skinny southern copepods.

Young salmon need to pack on weight to survive. But the El Niño-induced diet reverberates up the food web.

With less to eat, the survival of juvenile salmon and steelhead generally declines during El Niño years.

“The whole base of the food chain is based on celery instead of cheeseburgers, and it’s not great,” Laurie Weitkamp, a fisheries biologist with the National Oceanic and Atmospheric Administration at Newport, Oregon, told the Tribune last month.

To make matters worse, the northward creep of warm water also makes it inviting for predators that otherwise would find it too cool for their liking.

Fish like Pacific and jack mackerel, and other species in the tuna family, can both compete with young salmon for prey and eat them.

El Niño also brings the risk of adding fuel to marine heat waves that have plagued parts of the North Pacific, even during cool La Nina cycles.

El Niños appear about every 2 to 7 years and are most pronounced during winter months, according to the news release.

The agency is forecasting this iteration of El Niño to be moderate to strong in strength.