One of hundreds of tuna crabs that have washed ashore Fiesta Island.

A ban on U.S. Pacific sardine fishing that took effect July 1 will mean more food for starving sea lions, pelicans, and other creatures. But there’s no shutting down the other forces rattling the food chain.

Weird weather conditions are being linked to mass casualties and the stranding of sea creatures up and down the coast.

A giant plume of warm water known as “the blob” lurks about 1000 miles off the coast and is creeping up on California, pushing sea temperatures two to six degrees above average.

Then there’s the warming caused by El Niño, which has been gaining strength since March and may help the drought next winter, but it’s hardly helping sea life. Along with fueling new diseases and altering habitat, the warmer conditions weave a tangled food web.

“Warming, such as has occurred with the blob in the past 1-2 years, stratifies the water column,” says Dave Checkley of Scripps Institute of Oceanography. That reduces the availability of nutrients.

Left high and dry in May was the Velella velella, crepe-paper-thin cousins of jellyfish equipped with sails that washed up by the millions on county beaches, pushed and pulled by wind and currents. They made a rare appearance last summer, too, and a gusty winter El Niño was also predicted — but fizzled out.

In June, beaches were red with piles of crimson tuna crabs drawn up from Baja to become fish food and selfie-fodder.

Hot pink slugs called “nudibranchs” have been migrating from the south coast to populate the tide pools of Central and Northern California. Sea stars are still struggling with a wasting disease, which now seems to also be melting the spines off their prey; the urchins that have come out of hiding as sea stars disappear.

Among the worst off is the sea lion. In Southern California, the “unusual mortality event” of 2013 is no longer unusual. Now it’s called the 2013-2015 Sea Lion Unusual Mortality Event. According to NOAA, last year’s sea-lion crash was likely due to food scarcity, “especially sardines.” And this year is worse.

The Pacific Fishery Management Council, which regulates the fishing industry here, closed the commercial sardine fishery due to an estimated 90 percent decline in the stock since 2007. It’s the first shutdown since the one in the 1950s (chronicled in Steinbeck’s Cannery Row). In both cases, overharvesting combined with natural boom-bust cycles created a worst-case scenario. But a mystery remains.

According to the fishery management council’s website, warmer temperatures favor sardines, yet “temperatures in the Southern California Bight have risen in the past two years, but we haven’t seen an increase in young sardines as expected.” Checkley, the Scripps professor, considers it a matter of timing.

“The sardine population responds to long-term fluctuations in ocean conditions.” The recent warming is less important than a cyclical cooling phase (the “Pacific Decadal Oscillation”) that affected the North Pacific for the past 1-2 decades, says Checkley, who directs Scripps California Cooperative Oceanic Fisheries Investigations.

Since sardines live three to seven years, “this is the time scale the population responds to.” But the food cart is also tipped. Sardine feed on zooplankton, which eat phytoplankton. The smaller plankton sardines prefer has been scarce. Larger plankton is doing better, Checkley says — which should benefit anchovy. Sea lions love both of these forage fish. “But neither anchovy nor sardine has been available in abundance recently.”

It may have less to do with their population size than their availability, he says.

“The warm water has kept both away from the surface and shore, keeping the sea lions hungry.”

NOAA biologist Mark Lowry, who tracks the California sea lion population and studies their diet, says that in 2015 they’ve been eating “mostly shortbelly rockfish along with an assortment of other prey species.”

Studies by NOAA have found that other foods may not pack the same nutrition as sardines for mothers or newly weaned pups. Pup season began in June, and Lowry is busy with the count.

“I'm conducting an aerial photographic census right now but won't have any numbers until after the counts are made from the photographs,” Lowry says.

The tally won’t be known for several months, but Lowry is already predicting really low numbers.