One of the great mysteries in the cycle of salmon is how these fish know
where to go when they get to the ocean. They couldn't have
"remembered" their ocean migration route, because they have never been
there.
Scientists have learned some things about where they do go, by tagging the fish and by monitoring their ocean movement with electronic instruments. Yet very little is known about how salmon navigate. Onco may take day-to-day directions from the angle of the sunlight as it penetrates the seawater, or from water temperatures and ocean currents. The earth's magnetic fields might have something to do with it. But the best guess seems to be that they have a basic instinct imprinted in their genes. They just know without ever having had to learn. Different breeds of salmon follow different migration routes in the Pacific. Chinook are different from chum, sockeye or coho. Even among chinook, not all follow the same route as Onco. As far as scientists can tell, most chinook stay fairly close to shore. Some even take the Inland Passage, protected by green-wooded islands, up the coast of British Columbia and off the tail of Alaska. 
That's where Onco goes, swimming up to 15 miles a day. After two years in the Pacific - during the third year of her life - she has passed Anchorage and the Kenai Peninsula. At 21 pounds, she measures two and a half feet long and has a blue-green back and silvery-white belly. The two-tone coloring helps conceal her from enemies. Seen from above, she blends with dark ocean waters; from below, she blends with lighter sky. By now, she knows sea lions by sight and smell and avoids them. She has been chased by killer whales. Onco survives. 
During her third year in the ocean, she turns around and heads back down the coast. Traveling in a counter clockwise loop, she stays farther out at sea than before, but not by much. Less than 200 miles separate her from land's edge. As if responding to mysterious natural music that only salmon can hear, Onco knows to return to the Columbia River. She swims faster now. She is still eating and gaining weight. The cold ocean current is going her way and she covers up to 30 miles a day for months on end. Every salmon has its own time to return to fresh water. Not all kinds of salmon stay in the ocean three years. Sockeye and steelhead trout stay two or three years. Coho salmon seldom stay out that long. Even among chinook, the time spent at sea varies. Some chinook stay in the Pacific as much as five years before heading back home to spawn, but most stay out two or three years. And not all chinook come in at the same time of year. There are spring, summer and fall chinook. These are different runs of Chinook. Each is named according to the season they return from the sea. Onco is a spring chinook. Just before Easter in her third year at sea, she enters the mouth of the Columbia. 
Firm, plump, pink-meated, she's at the prime of her life. She weighs 28 pounds and is just a little less than three feet long. Onco is not the biggest fish here, but she is large. She carries scars from her adventures at sea. Behind the large fin on her back are tooth marks from a sea lion that just missed. A row of sea lice clings to her body, like tiny barnacles to the hull of a ship. Still, she is strong and healthy. Of the 200 smolts from Onco's redd that made it out to sea, only nine managed to avoid all the ocean perils and came back to the Columbia. That's not bad, considering the odds.  In fact, it's better than average in recent years for
adult fish returning. But not all of these fish will return to spawn. Luckily,
Onco misses a short gill-netting season by one day. But she has not yet escaped
the hooks of other fishermen.
Sportsmen patrol these waters waiting for the salmon. Their boats crowd together over "hot spots" where the fish are biting and where the law allows fishing. Onco would be a prize catch. Onco snaps at an apparently disabled anchovy. Sure enough, the anchovy has double hooks in it. A line is attached! Onco's first reaction is to dive deep and to swim away from the pressure on the line. That sets the hook deeper into the flesh of her mouth. At least she did not swallow it. Only one of the two hooks got her.  When her deep dive doesn't work, Onco
rises toward the surface. She slashes and twists, sometimes breaking the surface
of the water, to rid herself of the hook. Whenever she rests, she gets reeled in
closer to the boat. She dives again, rises again, trying to get loose. In fact,
the hook is working loose. If only she can muster enough strength to keep this
fight going. After 20 minutes, Onco is exhausted. She's very close to the boat,
now. She sees a large silver hoop-on-a-handle, with green nylon netting, pointed
her way.
With one ferocious leap and twist of her body, Onco rises out of the water. The hook tears from the loosened flesh of her mouth, and she falls - splash! -onto the water. Onco lies on the surface, stunned, for just a split-second. Then she rolls and swims downward, out of sight. She is truly the "big one that got away." |
