National Geographic : 1968 Aug
learned that, for most salmon, spawning is their final act before death. He has watched the emergence of tiny fish in spring time, and later seen them make their way downstream to the sea, to be swallowed by the ocean's immensity. He has wondered where they go and what they do in the years of their sea existence. And especially he has scratched his head in deep puzzlement over how they find their way back through the trackless ocean to the same river, the same tributary-the same riffle, perhaps -where they began life years before. Fishing Bears Warned by Intruder's Whistle The best vantage point I have ever had for watching the start of the salmon's life cycle was in the Brooks River, one of the major spawning streams supporting the great Bristol Bay sockeye runs of Alaska (map, page 208). I went there in late summer, 1966, to catch up on the latest developments in salmon research. A metal observation tower built by the United States Bureau of Commercial Fisheries stood in the middle of the stream so that observers could perch 20 feet up and spy on the spawning fish. 196 Nearing journey's end, sockeyes thrash in the seine of Canadian fisheries scientists in Shuswap Lake, British Columbia; researchers tag them (left) for the final swim to spawning grounds along the lower Adams River. The taggers record size and sex of each fish, an epitaph noted again within a few days when the dead fish line the river banks. Tallying the number that spawn helps conserva tionists estimate the future population and set limits against overfishing. More than a million salmon may make the run up the Fraser River system to the Adams, most of them arriving in a single week. The fish cover the 300 miles upstream in 18 days, traveling about 17 miles a day.