The Harbinger Seals of San Francisco Bay 

What will it mean if Harbinger seals disappear from the bay?

It's damn cold in the foggy gray pre-dawn at the Richmond Bridge. Two women -- Palma Formica and Christin Khan -- are stamping their feet and rubbing their palms at the toll bridge plaza. In a cramped upstairs room hidden behind rows of old street lamps, a pile of spare parts, and scattered Caltrans gear, they suit up in orange vests and harnesses with heavy metal D-rings on the back, then drive to an access point on the bridge's lower level. The pale green waters of the north bay fade into the silvery fog as Formica lowers their gear -- camera, tripod, binoculars, logbooks, and lunch -- to Khan, who stands on a platform just below the lower deck. It takes sure footing to clamber down the exterior ladder to a platform that hangs under the road face and then to squeeze first over and then under a series of bracing beams to reach the viewing platform on the opposite side of the bridge. "But this is nothing," says Khan. "Last year in February, there was a week of nothing but rain. I would go home, turn on the heat full blast, take a hot shower, put on my robe, and drink hot tea, and I would still be cold."

Khan and Formica reach the platform and immediately train their binoculars nearly straight down, where, about 50 meters away, a dozen plump harbor seals are perched on the tips of barely-exposed rocks in the bay just south of the bridge piers. "Remember, they can see us, so keep a low profile," Khan warns. By mid-morning low tide, nearly 80 seals have hauled themselves out onto a string of mini-islands, known as Castro Rocks.

The seals aren't the only action in the water: Three large barges maneuver into place at the base of the bridge's piers, bringing construction workers and equipment as part of a massive project to retrofit the bridge for seismic safety. One worker dons a wetsuit and tank and lowers himself into the water to work at the base of the pier. A loud horn sounds, causing many of the highly sensitive seals to raise their heads in alarm.

Not long after low tide, with 59 seals still sunning themselves during this vital rest period before heading back into the chilly waters of the bay, a small yellow rowboat emerges from the south. It's headed right for rock "F" -- the farthest outcropping from the busy bridge, and thus the most popular spot for seals. From up on the bridge, the four rowers are tiny, antlike -- but through binoculars they can be seen pointing toward the mossy green, seal-studded rock. With steady strokes they pass into a boat exclusion zone marked out by orange buoys. An anxious seal thrashes off her perch into the water, and a dozen others jerk their heads up -- and then follow suit. By the time the sightseeing passengers have had their fill, 44 of the resting animals have slid off the rock, swimming into deeper water to find safety.

Khan and Formica exchange exasperated -- and worried -- looks. "With this rising tide, those seals are not coming back," says Khan. "Most are going to give up, and that's cutting their rest period short." Formica scans the boat's hull for a license number, but to no avail. "It's illegal to do that," she explains. "But there's very little enforcement anyway. If we can see the boat license we can report it, but probably they'll just get a phone call or a letter saying, 'You shouldn't have done that.'"

Khan and Formica, graduate students in marine biology at San Francisco State University, are part of the Richmond Bridge Harbor Seal Survey. A collaboration between Caltrans and SF State, the survey is overseen by the National Marine Fisheries Service in an effort to monitor -- and, where possible, diminish -- the effects of the bridge retrofit on the resident population of harbor seals who use Castro Rocks throughout the year. Harbor seals have been protected under federal law ever since the National Marine Mammal Act of 1972, and their numbers along most parts of the California coast have largely rebounded. But that's not true in the heavily urbanized San Francisco Bay, where shoreline development has chased the seals from the quiet, secluded haul-out sites they favor. Researchers expect that the pile-driving, drilling, and just plain old hammering involved in retrofitting the Richmond Bridge is bound to scare away many, if not most, of the seals from yet another of the few remaining sites in the bay.

Given the pressing need to shore up the bridge, there's little that can be done to prevent the damage to the seals' well-being, aside from minor suggestions for changes in construction approaches. So wildlife experts are using the opportunity to record scientific data on aquatic mammal behavior and health before and during a major disturbance. What they're finding is that the bay could lose its only year-round population of marine mammals. And that's a double threat: There's not only the risk of havoc in the ecosystem when a top predator goes missing, but there's a host of implications for the beleaguered health of the bay. If it's not safe for seals, how safe is it for the rest of us?

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