A high price for fish

At a remodeled missile base on a cliff overlooking the San Francisco Bay, Joelle Sweeney is developing a cutting-edge technique to analyze sea lion feces. Her donors reside in a 10-foot tall fiberglass-paneled tank, of such high-tech luxury that it has been jokingly dubbed the Poop Palace. But Sweeney's work, at the bayside Marine Mammal Center, is deadly serious. The matter of just what, and how much, the California sea lions are eating may have something to do with why so many of them have recently been wounded by gunfire. Eighty-three sea lion shootings were reported along the coast of California in 2002, up from 19 in 1999. While the barking sea lions may charm tourists at Fishermen's Wharf, commercial seamen complain that the animals compete with them for salmon, even stealing the fish right off of their lines. The sea lions, they argue, are a leading reason for the decline in local fish stocks. Indeed, the number of California sea lions has increased more than 5% annually in recent years, with the current population at more than 200 000, according to federal marine biologist Joe Cordaro. Yet whether they are really the main culprits in the salmon decline is a matter of dispute. Sea lion defenders, including some scientists, say the issue is more complex, involving overfishing and declining habitat due to development of spawning grounds. But to date, these advocates have lacked solid – excuse the pun – data to back up their claims. Scat samples from wild creatures don't tell the whole story, since it is presumed that some bones have been digested away. That is were Sweeney and her Poop Palace come in. By keeping careful track of what her inmate sea lions eat, the 29-year-old Master's Degree student plans to produce a mathematical formula relating intake to output. Her 4-year project, funded with a $50 000 grant from the National Marine Fisheries Service, is one of the first controlled experiments of its kind. The key, Sweeney says, is to keep track of otoliths – fish ear bones, the size of which correlates with the overall size of the fish. Sweeney's formula may one day help let the embattled sea lions off the hook. But for now, violence against them is increasing, lending urgency to her task. The most recent casualty was Shopper, discovered in July lying in a Napa valley vineyard, killed by a single bullet just below his left eye. The 286-lb sea lion had garnered fame before his death because of his fondness for journeying far from his bay home. He got his nickname after being observed gazing into a motorcycle shop in Petaluma, where he was picked up by rescue workers and released into the Bay. One month later he was dead, his killing generating such outrage that a $14 000 reward has been raised for anyone providing clues as to the perpetrator. There have been few prosecutions under a 1972 US law making it illegal to harm or kill marine mammals. But at the Marine Mammal Center, a 30-year-old nonprofit hospital that supports rescues, rehabilitation, and scientific research, staff workers and volunteers are horrified by the violence. Center employees regard sea lions, otters, and other ocean-dwelling mammals not only as creatures worthy of affection and tolerance but as “sentinels” – living early warning systems offering important clues about the state of the seas and, for that matter, the world. The mammals' diets are worth studying in that context, and in fact, researchers at the Center and at nearby universities are increasingly focusing on this issue. Six years ago, for example, the Marine Mammal Center diagnosed the first case of domoic acid toxicity in marine mammals. A neurotoxin released by Pseudonitzchia australis (an organism responsible for some harmful algal blooms), domoic acid was first identified as a threat to humans in 1987, when three people died and more than 100 became ill after eating toxic mussels in eastern Canada. Since then, federal health officials have been monitoring shellfish, but in the 1998 case, illness among the sea lions was the first signal that something was wrong. Scientists say harmful algal blooms, or red tides, appear to be worsening, for reasons not clearly understood. In 2003, a shellfish biologist with the Washington Department of Fish and Wildlife warned a US congressional subcommittee that “virtually every coastal state is now threatened by harmful or toxic algal species, whereas 30 years ago, the problem was much more scattered and sporadic”. In another example of the marine mammals serving as furry canaries in coal mines, scientists and researchers have recently discovered a link between a pollutant parasite, Toxoplasma gondii, and the decrease in recent years in sea otter populations off the California Coast. Although other causes are also suspect, researchers from UC Davis studying otters living near freshwater runoff found that 42% of live otters and 62% of dead otters tested positive for T gondii. The parasite is believed to come from the feces of cats, washed into the sea by runoff or inadequate disposal of kitty litter. But what early warnings do stories of Shopper and other wounded sea lions deliver? Here, perhaps, they're just bringing reminders of an old, recurrent problem: man's inhumanity to mammal. Katherine Ellison

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