Editor’s Note: In late December 2009, the sea lions at Pier 39 in San Francisco vacated their home on the floating piers. This article may shed some light on what’s happening on the SF coast and the reasons for their leaving. Like many others, we wonder where they went and for what reasons.
PETER FIMRITE, San Francisco Chronicle, September 22, 2009
“Whale poop!” shouted several researchers in unison, as biologists scrambled to collect the floating reddish specimens Saturday as part of a comprehensive study of the ocean’s ecology off the Northern California coast.
The color of the whale excrement meant that the huge creature had been feeding mostly on a tiny shrimp-like crustacean called krill instead of fish and anchovies, its preferred food in recent decades. It is a change in diet that several bird species at the Farallon National Wildlife Refuge are unable to make, according to researchers in a joint ocean survey by the Cordell Bank National Marine Sanctuary, the Gulf of the Farallones National Marine Sanctuary and PRBO Conservation Science.
As a result, colonies of fish-eating cormorants, seagulls and murres failed to breed this year on the Farallon Islands. Over the past few months, dozens of dead birds and even sea lions have been found on local beaches.
Anchovies have disappeared, and scientists don’t know why. The researchers on the vessel believe that, in their absence, birds and mammals like humpback whales that eat krill are thriving while the ones that are eating only fish are in trouble, and the whale excrement served as evidence.
“We’ve had an extraordinary number of dead animals,” said Jan Roletto, the research coordinator for the Gulf of the Farallones National Marine Sanctuary. “It seems to be that the animals that suffered the most were the animals that forage on anchovies.”
Brandt’s cormorants, a black bird with white plumes that can dive as deep as 300 feet for its prey, did not produce any chicks this year on the Farallones or on Alcatraz. That’s compared with 15,000 chicks in 2007.
For the anchovy-loving bird, it was the first complete breeding failure in 40 years during a year without El Niño conditions so far, according to scientists at PRBO, formerly known as the Point Reyes Bird Observatory.
Western gulls and common murres produced about one-seventh of the number of chicks they normally hatch. Researchers on the Farallones reported an increase in predation on the chicks that were produced, mainly because the parents were too far away looking for food.
Beachgoers probably noticed the death toll. Six to eight times the normal number of dead cormorants and sea lions were found on Bay Area beaches in May, June and July, according to researchers. The death toll in each case involves birds and marine mammals that prey on anchovies and other fish.
The deaths and breeding failures are all the more troubling because there appears to be plenty of krill, rockfish and other prey species to feed the seagoing birds and mammals.
Jaime Jahncke, the director of marine ecology for PRBO, said common murres had previous breeding failures in 1982-83 and in 1991-92, but both times the problems were linked to El Niño, a weather condition associated with warmer ocean temperatures and atmospheric conditions that cause heavy storms. Although forecasters say an El Niño is forming in the tropics, it has not yet hit California, Jahncke said.
“I don’t know what it means, but it’s not good,” Jahncke said. “There are a lot of changes happening, and none of them have a clear explanation.”
Seagoing birds and mammals near the Farallon Islands depend on krill, anchovies and other prey that are attracted to conditions produced when cold, deep ocean currents bounce off the underwater outcropping called the Cordell Bank, forcing nutrients upward. The nutrients are most abundant during the transition from winter to spring.
Spring arrives an average of 20 days earlier than it did in 1970, Jahncke said. There has also been an increase in the strength of the upwellings over the past two decades, he said.
Apart from the lack of anchovies, that is probably a good thing.
The team of scientists on the boat spotted several blue whales before the humpback put on its show.
The abundance of blue whales, which feed almost exclusively on krill, and the evidence provided by the humpback made it clear that there is plenty of krill in the ocean.
“Whales primarily over the last decade have been feeding on fish,” said Lisa Etherington, the research coordinator for the Cordell Bank National Marine Sanctuary. “The last couple of years they’ve been feeding on krill. We don’t know why.”
Jahncke said salmon smolt also feed on krill, a fact that may or may not help the beleaguered Central Coast chinook. The Cassin’s auklet, a small, chunky seabird that feeds on krill, had above-average nesting success this year.
But wild fluctuations are now almost normal, according to the researchers, who are concerned that the El Niño predicted for next year will cause a further decline in the numbers of birds.