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WRITTEN BY WILLIAM DIETRICH
PHOTOGRAPHED BY TOM REESE
When predators are protected, what hangs in the balance?
Here in our Northwest, all endangered species are equal, too. But those higher on the food chain may be more equal than others.
At least that appears to be the case in regard to seals and sea lions. The Marine Mammal Protection Act of 1972, sponsored by former Washington Sen. Warren Magnuson, has resulted in a population explosion of those critters at the same time that fish stocks have been swimming toward near-extinction.
It's not just salmon and steelhead. Hake, another commercial fish species, have declined about 98 percent in Puget Sound, noted state Fish and Wildlife Department biologist Wayne Palsson, and the fish are a favorite of sea lions. Petitioners have nominated 18 species of bottom fish here for listing, and almost all are marine-mammal chow.
In contrast, ratfish by far our most common fish, making up 40 to 50 percent of the fish biomass in Puget Sound are a deep-dwelling species that seals and sea lions rarely dine on.
Crisis? Actually, some scientific data suggest that wintering sea lions have sharply declined in number in Puget Sound since their peak in 1996, presumably because there's not enough food. And harbor-seal numbers, which increased from 5,000 in Washington to an estimated 40,000 since the Magnuson law, recently appear to have stabilized, said marine-mammal biologist Harriet Huber.
So, is nature coming into happy balance? Or are natural predators undermining fish-rescue efforts, given that a seal can eat five pounds of fish per day and a sea lion as much as 50 pounds?
Steve Jeffries, another biologist with state Fish and Wildlife, estimates that marine mammals today eat at least five times as much fish in this state as they did in 1970. "Seals and sea lions are not the reason salmon are in trouble in this state," he said, "but they certainly are a factor in any recovery of salmon stocks."
Congress asked just that question a few years back. In 1997 a panel of scientists assembled by the National Marine Fisheries Service replied that the issue is complex, the answer murky, the questions need more study. And that's where we're at today.
SCIENTISTS WITH the National Marine Mammal Lab at Seattle's Sand Point now feed collected seal poop into washing machines and microscopically examine the tiny bones that emerge. Otolith "ear" bones can reveal the species and age of ingested fish. DNA bone testing done by federal labs at Montlake accomplishes the same thing.
The nightmare driving such study is the specter of Herschel, the California sea lion who made a smorgasbord of steelhead heading for the fish ladder at the Ballard Locks. The man-made dam at the locks forces the fish to pause in their annual migration, and man-made mammal protection brought California sea lions into Puget Sound in search of food. The first recorded local sighting of these other Californians was in 1978, six years after the Magnuson Act passed, said Bob DeLong, another marine-mammal researcher.
By 1984, scientists were aware the newcomer sea lions were making a significant dent in the Ballard Locks steelhead run. They also learned that only about 10 of the more than 1,000 sea lions in Puget Sound accounted for most of the problem: a small group had learned of the bonanza and kept it to themselves.
They swam back in days.
So the sea lions were caged again, shipped this time back to their breeding grounds in southern California.
They swam back in a few weeks.
Studies, debate and experiments ensued. By the time authorities had permission to remove five animals by killing them, 12 years had passed. Herschel was long gone, his fate unknown. But three replacements Hondo, Bob and Big Frank were captured and shipped by Federal Express airplane in 1996 to a life sentence at Sea World in Orlando. Two more troublemakers near tribal nets mysteriously disappeared.
Other sea lions didn't take their place, but it wasn't because they feared capture, underwater noise-makers or, at one point, an experiment with a fake plastic killer whale. Rather, it was because the run of 2,500 steelhead had collapsed to as few as 70 fish, and the free lunch was over.
The steelhead are still far from a healthy recovery and the lesson of the fiasco is far from clear. Dams everywhere have made salmon and steelhead easier prey. So are clever marine mammals at fault for finding an easy meal? Should they die for our obstructions?
This kind of conflict wasn't envisioned when the Marine Mammal Protection Act was passed almost three decades ago. Harbor seals and sea lions were hardly mentioned; rather it was the outcry about whale hunting, dolphins trapped in fishing nets and the clubbing of baby harp seals that drove the legislation.
Yet humans had been killing seals and sea lions for a long time. Aboriginal populations used them for food and 19th-century hunters sold sea-lion whiskers, testes and penis bones as aphrodisiacs to China. Modern civilization regarded them as competitors for valuable fish species. Sea lion hides were used for glue and sea-lion meat was ground into dog food.
Some 27,000 harbor seals were deliberately killed with depth charges in Alaska in the 1950s to protect fishing grounds. Some 40,000 to 60,000 seal pups were slaughtered annually in the 1960s for the European fur market. Oregon, Washington and British Columbia all put bounties on harbor seals in response to fisherman demands, driving local populations to near-extinction.
Yet the more biologists learned about marine mammals, the more remarkable the animals seemed. If Magnuson deserves credit for helping save them in 1972, it's their own grace, charisma and extraordinary physiology that make a return to widespread harvest almost impossible to imagine in the 21st century. Seals and sea lions are just too dang fascinating.
HARBOR SEALS and sea lions belong to a group of 33 species of marine mammals called pinnipeds, from the Latin pinna, meaning fin, and pedis, meaning foot. The fin-footed mammals are believed descended from the same terrestrial ancestors that gave rise to bears and dogs, and they are equally smart, quick-learning and adaptive.
A California sea lion named Rocky was taught a simple language of six verbs, five adjectives and 11 objects and could comprehend about 7,000 different sentences using those words. For example, "Ball, black pipe, fetch," means, "Take the black pipe to the ball." A New England Aquarium harbor seal named Hoover was able to mimic a few English words.
If marine mammals are so smart, why did their air-breathing terrestrial ancestors ever choose the cold, wet sea? Because food is more plentiful in the ocean. We can see examples of possible future transitions today. One type of pig wades the coral reefs of the Tokelau Islands in the Pacific to feed. In Scotland certain sheep swim to offshore rocks to eat seaweed. Maybe, millions of years from now, there will be marine pigs and sheep.
If so, they'll have to make some of the same kinds of astonishing adaptations found in seals and sea lions. Both mammals, for example, maintain body temperatures close to our own about 100 degrees yet live comfortably in 45-degree water that would kill us in minutes or hours. Water leaches heat 25 times faster than air.
COMPACT, HEAVY bodies help: Adult harbor seals weigh about 180 pounds and sea lions 500 to 700 pounds. Their blubber and fur is so effective as an insulator that they have more trouble cooling than staying warm. They also have a versatile circulatory system that helps conserve their blood heat when cold or send it flushing from their skin when warm. Their blood-volume ratio to their body weight is almost double that of land animals.
Water conveys a kind of weightlessness. Both species are awkward on land but have a torpedo shape in water than lets them cruise at speeds of 5 to 15 knots. Sea lions can sprint as fast as 30 knots, equivalent to a speedboat, and drive themselves fully out of the water to leap like a porpoise.
Both species have been recorded diving to depths of 600 feet, sea lions to 700 feet, and both can stay submerged for up to half an hour. They actually exhale to make diving easier, relying on their large blood volume, a dramatic slowing of their heartbeat and a special blood compound called myoglobin to conserve oxygen. If knocked unconscious their lungs are automatically closed off to prevent filling with water.
Seals prefer to sleep on land but can sleep underwater, automatically surfacing periodically for air. More commonly, they assume a posture called bottling, drifting on the surface with just their nose sticking out as they doze.
Unlike humans, pinnipeds are able to drink sea water if they have to. Their kidneys are so efficient that they can extract the salt and have a small net gain of fresh water. Yet seals seldom bother, instead getting 90 percent of their fresh water from the water present in the fish they eat. And while we get thirsty in hours, male sea lions can go up to three months without food or water while defending their territory in California breeding rookeries.
Harbor seals and sea lions use sound like we do above water, to communicate with barks, grunts and roars. To a still-unknown degree they use echolocation, or sonar, to navigate, like whales and dolphins. In water they can hear high frequencies inaudible to us, living in a rich repertory of noise.
Yet they are also intensely visual animals, using their large eyes for the equivalent of almost 20/20 vision underwater, though they are a bit near-sighted above.
While they can't smell underwater, pinnipeds have a good sense of smell on land. And their whiskers are so sensitive that they can detect the vibrations that potential prey make in the water, helping them hunt. Experiments have shown that Arctic and Antarctic species use the whisker vibrations to help find openings in overlying ice.
PINNIPEDS DIFFER in lifestyle. Harbor seals are homebodies, rarely straying more than 25 miles from where they were born. California sea lions, in contrast, are seasonal migrants. They breed in Southern California's Channel Islands or Mexico in the summer. The animals we see here are males that migrate north in the fall in search of the food necessary to grow to full size and thus compete on the breeding grounds for females. They roam thousands of miles, probably navigating with a combination of magnetism, scent and memory.
Their wintering numbers in Puget Sound peaked at about 1,300 in 1996 and have fallen to 200 or 300, presumably because of the decline of all kinds of fish stocks here. Thousands still move up and down the Washington coast, however, and the total sea-lion population is quite large, perhaps 200,000 animals in California and 100,000 more in Baja California. Scientists estimate the population may have been as low as 50,000 when the Magnuson Act passed.
Counting harbor seals is not easy. Scientists can tally the number hauled out on rocks or beaches at the daily peak, usually low tide, but it took years of research to correctly estimate that the rock count represents just 60 percent of the population; the rest are in the water. Today they total nearly 40,000, up from an estimated 5,000, and only recently has their growth curve appeared to level.
If a juvenile survives to adulthood it can live two decades as a male or three as a female, breeding after the age of 5. With few enemies besides killer whales, there would seem to be no limit to their numbers.
Nature can adjust, however, because pinnipeds have developed a strategy that allows them to give birth and then mate again in a single season. An egg can be fertilized by a male but won't attach to the uterine wall for weeks or months until the mother has completed nursing her pup, molting her fur, and regaining her strength. If food is scarce, fetal development won't occur at all.
Female seals usually have just one pup at a time and have been observed rejecting one of their young if there's a rare twin birth. They keep their young alive in the cold water with a milk that is about 50 percent fat and 10 percent protein, compared to 3 percent fat and 2 percent protein in human milk. While it's common to see pup and Mom together in local waters, instruction ends with weaning and the pup is on its own. Sea-lion mothers, in contrast, continue to teach their young after weaning.
LIKE OTHER marine mammals, pinnipeds can sometimes be observed in play. California sea lions are expert at body surfing.
And they eat, big time. Pinnipeds tend to swallow their food whole or in large chunks and are believed to have little sense of taste. On the West Coast they eat 134 separate species of seafood, including salmon and steelhead smolts and adults, hake, herring, squid, rockfish, cod, crab, octopus, sardine, smelt, sculpin and pollock.
Federal studies suggested sea lions in Puget Sound were consuming between 830 and 2,064 metric tons of fish per year in the mid-1990s. Harbor seals were consuming about 31,500 tons in the state as a whole. Since those estimates, sea-lion numbers have declined in Puget Sound but grown on the coast, and harbor-seal numbers have almost doubled.
Roughly, that suggests the total seal and sea-lion consumption is somewhere between 50 and 100 million pounds of fish each year in this state.
Yet scientists also noted that as of 1995, the human catch on the West Coast was twice that of seals and sea lions. The animals' direct impact on salmon fishing is significant but not decisive: One study showed sea lions grabbed 12 percent of California troll-caught salmon in 1996 and about the same amount in Washington gillnet fisheries.
In Alaska, the situation is reversed: human overfishing of pollock is being blamed for a Stellar sea-lion population collapse. The number of sea lions has dwindled from about 140,000 in 1960 to 16,000 today.
SO: IS THE marine-mammal comeback a wonderful success story? Or an ill-planned population explosion that is undermining fish-recovery efforts?
It depends on your perspective. Fish and Wildlife's Jeffries said common-sense management should be the ultimate goal. "Killing them all or not killing any are two extremes," he said. "In the middle are the resource managers. I just don't think that in the year 2001, man can just step back and say everything can take care of itself."
The Marine Mammal Lab's DeLong, in contrast, isn't sure there's a problem at all. Marine mammals spread their feeding among many species, he points out, and tend to prey on the most abundant, not the weakest. When humans fish, the biomass leaves the sea. When marine mammals fish, much of the productivity of the ocean is simply recycled through waste and decomposing mammal bodies: lower organisms eat it and keep the nutrients in the food chain.
"Is there an ecological impact? Not that we've been able to identify," DeLong said. So complicated is the sea, and so efficient is it at restocking natural predation, that, "If you remove predator pressure, there's not necessarily more fish."
The truth of the matter is that it is we homo sapiens who've set in motion huge swings in the populations of plants and animals, and we're just becoming aware of the consequences and trying to understand them. The Marine Mammal Protection Act and Endangered Species Act slammed on the brakes in our Northwest. Now we're in a skid, fighting to bring things under control.
William Dietrich is an author and former Seattle Times reporter. Tom Reese is a Seattle Times staff photographer.
|Cover Story||Plant Life||On Fitness||Northwest Living||Taste||Now & Then|