More than 40 miles out from the Golden Gate Bridge and over an undersea slope plunging from the edge of the continental shelf, a team of scientists lowered a specialized net into the cold, green Pacific Ocean.
Soon, the research vessel Fulmar, a 67-foot aluminum-hulled catamaran, began towing the net above the slope, known as the "shelf break," for a tiny but titanically important creature called krill.
Jaime Jahncke, director of marine ecology at Petaluma-based PRBO Conservation Science, already knew the catch would be slim.
"Honestly, right now there's not much of it here," Jahncke said last week aboard the Fulmar.
Echo soundings displayed on a screen inside the Fulmar's cabin showed a relatively small mass of krill, a transparent, shrimp-like crustacean, in the depths below.
Why the krill had cleared out wasn't clear, Jahncke said. And the meaning of the results on this particular day are neither good nor bad. But the consistent monitoring of the area enables scientists to assess patterns in the marine ecosystem, including possible impacts of climate change.
Last year, abundant krill drew record numbers of humpback and blue whales to the Farallones, and Cassin's Auklets, birds that dive 100 feet or more to catch krill, had unparalleled breeding success on the rocky islands.
Krill, found in all oceans of the world, are a cornerstone of the marine food chain. The half-inch long animals live in massive swarms, eating microscopic phytoplankton, and are, in turn, devoured by fish, seals, squid, penguins and even 40-ton whales.
Last week the scientists stationed on the Fulmar's top deck saw few birds or marine mammals in waters known as one of nature's most abundant pantries.
"There doesn't seem to be a lot of food," said Kirsten Lindquist, a field biologist with the Farallones Marine Sanctuary Association.