Fisheries Issues in the News
Wednesday 30 June 1999
Salmon use sun, familiar smells as guide back to birthplace
They're back again. Hundreds of silvery Puget Sound salmon, soon to be thousands, leaping up local streams and fish ladders and posing for snapshots behind the underwater window at the Ballard locks.
Despite their newfound status as endangered species, there will be plenty of salmon to astound tourists and natives, who once again will consider the salmon's saga and ask: How do they do that?
How does a Puget Sound fish traverse thousands of miles of ocean, yet return faithfully to its native river and stream to spawn? How does it distinguish between one river and the next? How does this seemingly primitive creature exhibit navigational abilities that rival man's most-sophisticated technology?
The short answer: Nobody knows.
But scientists are working on it. And now the question may be more timely than ever, since that homing mechanism is what determines the genetic differences between one run of salmon and the next - and between one that is endangered and another that is not.
From his corner office at the UW School of Fisheries, Quinn looks over Portage Bay and the artificial rearing pond and concrete fish ladder that have been the scene of salmon research for half a century. It was here, in the early 1950s, that scientists demonstrated the extraordinary homing instincts of the Pacific salmon.
The experiment went like this: Juvenile coho salmon from Soos Creek were moved to two alternate sites - the university and the Issaquah hatchery - then marked and released into the lakes, where they migrated to the ocean for two or more years. "When they returned as adults," Quinn says, "UW fish returned to the UW, Issaquah fish returned to Issaquah, and none returned to Soos Creek."
This established that the salmon's navigational impulse is primarily learned, not inherited, Quinn explains. If the trait had been inherited, the fish would have been drawn back to Soos Creek.
Lost with a plugged-up nose
Streams differ in chemical composition, Quinn explains. Each has its own unique mix of minerals, plants and chemical scents, which might not be detectable to humans but make a big difference to fish.
Salmon appear to learn the odor of their stream very soon after hatching. Each fish becomes "imprinted" with the distinct smell of its native stream. "It is spontaneous learning," Quinn explains. "There is no reward, no punishment, no reinforcement, positive or negative."
The fish then go to sea. The creature will not need the odor information until its return migration, one-to-three years later. But the memory persists. As the fish approaches its home territory, it will begin picking up traces of its native stream. Molecules of water will pass into the fish's olfactory "capsules," nostrillike openings in front of the eyes, and past sensory tissues which detect the distinct odor of the home stream.
The scent need not be natural. In another UW experiment, water in the salmon-rearing pond was tainted with artificial chemicals before the juvenile salmon were released. Years later, the returning fish were drawn to the artificially tainted fish ladder.
Either way, the homing instinct is nearly perfect. Of the fish that survive in the ocean, about 98 percent will find their way home to spawn. But even the 2 percent or so that stray serve a critical biological function. They expand the domain of the species.
If not for these errant fish, Puget Sound would have no salmon. Some 12,000 years ago, Western Washington was encased in ice up to a mile thick. As the glaciers retreated, they carved a new topography, a process that continues today.
Salmon had to start over again. Repopulating Puget Sound required at least two stray salmon, a male and female, from distant runs that were not glaciated. Ever so gradually, those occasional strays gained a finhold in one river, then another. As a result, the oldest Puget Sound salmon runs are a few thousand years old - a mere wink of an eye in evolutionary time.
Something else at work
If smell leads salmon to their stream, it certainly does not work in the ocean, scientists say. Even if a fish could detect the scent of a single stream from hundreds of miles out at sea, it could not determine which direction it came from. Something else is at work out there.
Researchers have investigated numerous theories: minute differences in salinity, water temperatures or dissolved oxygen. Quinn's model, proposed in 1982 and now widely shared, suggests salmon use a combination of several devices:
-- An internal "map" of the North Pacific, based on Earth's magnetic field.
-- A celestial compass with a backup magnetic compass that might actually incorporate tiny magnetite crystals inside the salmon's brain.
-- An internal clock that enables the fish to determine its latitude based on the sun's position.
Lots of animals, from bees to gray whales, migrate over long distances, Quinn says. They use a variety of navigation techniques, but many appear to be learned. Birds, for instance, tend to follow their mothers. So do whales.
It seems that animals learn the transit of the sun across the sky and combine this information with an internal clock, Quinn explains. Migrating birds, kept in captivity, will at the appointed time begin to hop in the direction they yearn to fly.
But salmon are all first-time migraters. Since they die after spawning once, none gets a second chance. There is no old-timer to follow and no opportunity to learn by experience.
To do that, they may actually use those tiny crystals of magnetite, which serve as tiny compass needles, to align themselves with the magnetic poles.
Far-fetched? Sharks detect magnetic fields electrically, including fields induced by their own own movement. Still, Quinn is cautious.
"All of this is still pretty speculative," Quinn says. "We're talking about an entire sensory system that we don't understand. But I think we're getting closer."
Like the salmon's journey itself, the mission is more than intellectual. Quinn believes that the more we learn about the salmon's navigational abilities, the more we learn about the capabilities of human beings.
He thinks of ancient Polynesians who navigated across thousands of miles of the South Pacific or Eskimos who traversed vast expanses of Arctic wilderness seemingly devoid of landmarks.
"We know that magnetic field detection is present in honeybees, sharks, bees, fish, even primitive organisms such as nudibranchs. So why not human beings?"
Sunday 27 June 1999
Sharp rise in chinook salmon jacks pleases fisheries managers
SPOKANE - A sharp rise this year in counts of Columbia River chinook salmon jacks - males that return from the ocean to spawning grounds a year or two early - has fisheries managers optimistic that ocean conditions are improving for the Northwest's dwindling salmon runs.
Steve King, salmon fishery manager for the Oregon Department of Fish and Wildlife, said last week that this year's count of jacks at the Bonneville Dam - about 30 miles east of Portland - is the highest since 1976.
"This indicates improved runs may be coming the next couple of years," King said.
For reasons that mystify biologists, the precocious jacks make their way up the Columbia-Snake system to spawning grounds the year after heading downstream as juveniles. Salmon typically spend two to three years in the ocean.
The number of chinook jacks counted at dams as they swim upstream is seen as an indicator of how many of the more numerous, fully grown chinook will return to spawn over the next two years.
As of last week, 10,597 spring and summer chinook jacks had been counted at Bonneville Dam for the year, according to the Portland-based Fish Passage Center, which collects fish counts from throughout the Columbia-Snake system. That's more than six times the number counted as of June 24 of last year - 1,674 - and more than three times the average for the same date for the 10-year period 1989-1998.
The total of chinook adults counted is slightly down compared with the same date last year - 47,526, compared with 48,953 last year - but is good considering the small size of the runs when those fish were juveniles in 1996 and 1997, said Larry Basham, a Fish Passage Center biologist. The outlook for other Northwest salmon runs also is generally good this year, he said.
Thursday 17 June 99
Atlantic salmon escape into Sound from pens
It may be a fisherman's delight or an environmentalist's nightmare, but 100,000 Atlantic salmon that escaped from a commercial fish farm are swimming free in Puget Sound this week.
The Atlantic salmon, weighing up to 9 pounds each, escaped from a commercial fish farm at the south end of Bainbridge Island on Sunday. Northwest Seafarms, the owner, reported that steel rings snapped under pressure during the extreme high and low tides, opening a gap in the pens.
The unusual tides also cause powerful currents, which are expected to scatter the fish quickly.
The escape is of concern to environmentalists and fisheries officials who fear the non-native fish will introduce disease or even interbreed with native fish, undermining already troubled Puget Sound salmon.
But the incident also creates a rare opportunity for sports fishermen, who are asked to help track down the escapees.
It was the second massive escape in two years from the Bainbridge farm. In 1997, an estimated 300,000 Atlantic salmon escaped from the Bainbridge net pens, then owned by Global Aquaculture.
Sports fishermen had a field day, hooking thousands of the escaped fish. This week's opportunity is more complicated. State officials have decided not to open the immediate area to fishing, for fear of accidentally catching Puget Sound salmon listed as endangered.
But areas south of the Southworth ferry dock are open, said Kevin Amos of the Washington Department of Fish and Wildlife. The area around Bainbridge will open on July 1, but with restrictions on gear.
The Atlantic salmon are distinguished from native Northwest species by the large round black spots on their cheekbones, fishery officials said.
Friday 5 June 99
Coastal fishermen wary of U.S.-Canada salmon deal:
Here's the essence of the new U.S.-Canada salmon agreement:
Both sides agree to conserve Pacific salmon by killing fewer of
them.
And here are the details: U.S. fishermen will kill fewer Canadian
fish, and Canadian fishermen will kill fewer U.S. fish.
Simple as it sounds, it took more than six years, millions of dollars
and scores of private and public meetings between high-level
diplomats to reach the agreement announced yesterday by U.S.
and Canadian officials.