Weather Watch

Record atmospheric river paves way for ‘above average’ coho salmon run

The mouth of Cayucos Creek. Strong water flows and large waves this winter have produced a clear path to the ocean.
The mouth of Cayucos Creek. Strong water flows and large waves this winter have produced a clear path to the ocean. Special to The Tribune

Atmospheric rivers have made this year one for the record books. There have been 10 atmospheric rivers so far this rain season — defined as the 12-month period of July 1 through June 30. It’s the most I’ve ever seen.

As I have written before, these rivers in the sky can stretch for thousands of miles across the ocean and are often formed by massive storms drawing ridiculous amounts of water vapor into narrow bands ahead of cold fronts.

They can carry more fresh water than the Amazon River.

Along the West Coast, they are informally called the “pineapple express,” which is a subset of an atmospheric river event that originates in the tropical waters near Hawaii — hence the pineapples. In the past, meteorologists referred to these as “the hose.”

Many locations along the northwestern San Luis Obispo County coastline and into Northern California have seen record-breaking amounts of precipitation and water flows into creeks and rivers for the combined months of January and February. Rocky Butte near Hearst Castle has recorded about 60 inches of rainfall over the past two months.

These atmospheric rivers provided the water our state desperately needed after five years of horrific drought, filling many of the state’s lakes and reservoirs, but they also produced significant flooding and damage to California’s infrastructure. Locally, it may be months, if not longer, until you can drive the stretch of Highway 1 between Ragged Point and Carmel, perhaps the most beautiful highway in the United States.

The drought followed by record rainfall has not only affected our roads and dams, but also our wildlife, such as coho salmon in Northern California.

The drought followed by record rainfall has not only affected our roads and dams, but also our wildlife, such as coho salmon in Northern California.

These fish have a fascinating life cycle. After hatching in streams and creeks from November through April, depending on the water temperature, these translucent alevins, or fry, spend the first few weeks hiding in the nooks and crannies between gravel until their yolk sacs are absorbed. After emerging from the gravel, they become silver to golden in color and start to feed heavily and grow quickly. As they quickly grow, they become parr, or juveniles, and move into deeper and deeper pools in their territory.

After one year in fresh water, they migrate downstream to the ocean as smolt, primarily in the months of March and April, when the sand bars that form at the mouths of many California coastal streams are no longer blocking their journey to the sea. It’s believed that the young salmon form into schools and move along the continental shelf to feed and grow.

After two years in the ocean, the adult coho salmon migrate up the rivers and creeks whence they first hatched.

However, a few salmon known as “jacks” or “grilse” return as 2-year-old spawners. This migration usually occurs between November and January, when anticipated rains and heavy runoff open the sand bars. After spawning, they quickly pass, completing their three-year life cycle.

In 2014, tiny amounts of rain fell from the sky. What did fall was quickly absorbed by the parched soils and vegetation. There simply wasn’t enough rain runoff or wave energy to open the sandbars at the ocean’s edge. Consequently, the 2014 adult salmon cohort had no path to the streams and creeks.

Our dedicated and knowledgeable state fish biologists hypothesized that the 2017 salmon run would be a disaster since very few of the 2014 class were able to spawn and hatch babies. They worried that every third year in the future, they would see minuscule salmon runs, further threatening this beautiful animal’s survival.

Well, it turns out, state fisheries’ biologists are reporting well above average coho salmon runs this year. Tracker tags embedded in the fish indicate that much of the 2017 salmon run were fish that hatched in 2013. The biologist determined that the 2013 cohort spent another year in coastal streams and creeks before the “very strong 2015-16 El Niño” that produced heavy rainfall in Northern California cleared their path to the ocean. Consequently, the salmon attempting reach the coastal streams and creeks in 2014 spent an additional year at sea.

In other words, the tracker tags indicated that many of the coho salmon in the 2017 run were 4 years old, versus the normal three-year life cycle. That’s probably the human equivalent of 100 in salmon years.

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John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter: @PGE_John.

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