As any alert detective-story reader will immediately recognize, the illustration on the opposite page looks like a thumbprint. It contains those whorls, ridges and irregular patterns that, we are told, are never the same for two human thumbs, and thus are the definitive means of identifying human beings. Actually, this seeming thumbprint can do a good deal more: it is one of the scales of an adult sockeye salmon (below), as seen under a microscope, and it not only can identify the fish but can tell where it was spawned and where it is going.
In a startling ichthyological melodrama rivaling any paperback thriller, these scales have just helped establish a point that has kept biologists and fisheries experts on the edge of their laboratory chairs—a point that is momentous to sport and commercial fishing everywhere. On the Horsefly River of British Columbia, where scientists watched and worked and waited through tense days, the scales proved beyond question that salmon can be restored in immense numbers—by the millions, in fact—to barren but once-abundant streams. Identification by scale has made it possible to regulate salmon fishing in a systematic and selective way, and assure that the fish returning to a depleted stream to spawn will get there and rebuild their former populations. A quarter century ago the Horsefly, once one of the great salmon streams of the fabulously rich Fraser River system, numbered its returning salmon barely in the hundreds. But after what happened there last month, the culmination of an experiment hopefully begun eight years ago, fish biologists are prepared to say that runs of salmon and other migrating fish, given proper pollution control and a way of circumventing barriers such as dams, can be preserved and built up again on any river anywhere. As Clarence Pautzke, Commissioner of the U.S. Fish and Wildlife Service, put it succinctly, "No stream can be written off." What it could mean, said one eminent authority, is the return of game fish to all the streams where they were once abundant.
The sockeye is not a game fish, but salmon are so closely related that what applies to one species is generally applicable to all in matters having to do with conservation and control. In the center of each sockeye-salmon scale the rings have grown close together; these are growth rings formed in a salmon's first year in a lake, and they differ for every lake. The Horsefly salmon, for example, after being hatched swim 30-odd miles down the river and into Quesnel Lake. They spend their first year there and acquire a scale pattern different from that of the salmon spawned in the Stuart River, the Chilko, the Raft, or any of the other streams that make British Columbia the greatest salmon-producing region of the continent, if not the globe.
These young salmon from the Horsefly are three-inch fingerlings after a year in Quesnel Lake. They swim the Fraser to its mouth and in the first week of May join millions of salmon from other rivers before heading out to sea. Fisheries scientists trap them there and take samples of their scales. Plastic replicas are made and filed in small loose-leaf notebooks, about 4 inches by 7 inches, each page containing 115 replicas of scales. Thus, when the fish return three years later as adults, they can be identified as surely as though they were tagged by species and home addresses, and their return upstream can be regulated accordingly.
That circumstance and the history of the Horsefly made this fall one of the most dramatic ever known in northwestern fishing. The story began in a narrow valley deep in the heart of the Cariboo country of interior British Columbia during a few days of perfect Indian-summer weather last month. The Horsefly River is a bright, short, shallow, crystal-clear little stream that springs from two branches on the slopes of Mount Perseus, an 8,361-foot cone that the natives call Haycock Mountain. In its extreme upper reaches, the Horsefly flows 30 miles or so through deep wilderness and into a rocky chasm, heavily wooded on steep slopes that rise 800-odd feet above the water. The Horsefly at this point is 30 feet to 50 feet wide, and at the end of a dry summer perhaps four feet deep; it is a noisy, wild, turbulent stream with beautiful coiling rapids that seem to wind and unwind as the river is thrown from one canyon will to the other. As it emerges from its gorge it drops over a series of falls. Below the falls the river widens to 100 feet, slows down, warms up and flows with unhurried speed over miles of tranquil little rapids and riffles.
Centuries ago the sockeye or red salmon, Oncorhynchus nerka, bright-red fish weighing on the average six pounds and measuring 24 inches in length, selected this particular stretch of the river for its spawning beds. Every four years, 25 times each century, from time beyond reckoning, these salmon came from the North Pacific, forced their way up the Fraser River (swimming from 17 to 33 miles a day), passed hundreds of thousands of places that you or I might think would be fine for spawning, and unerringly reached this one little section of the Horsefly. If anything prevented their reaching it, they died without spawning.
Salmon live 12 days on their spawning grounds. Five days are spent preparing to spawn. The fish pair and select the right kind of riffle, with the precise kind of gravel and the right stream flow. Another five days are spent preparing the redd, the nest in the gravel. The female scoops this out, lying on her side and flapping her tail, the current of the river carrying the sand away. Two days are spent spawning. The female hovers, suspended over the sand of the excavation she has dug, the male pressing against her, and as she deposits some of the eggs she carries, the male at the same instant fertilizes them with his seminal fluid. The female now digs another nest upstream, the sand and gravel from this covering the eggs she has just laid, and so on with several hundred eggs in each nest until 3,000 to 5,000 have been laid. Both male and female die after spawning, reduced to only one-third what they weighed when they entered fresh water. The eggs develop under the gravel, where they are safe from predators, and the fry work to the surface of the gravel when the water warms in the spring. Then they are swept downstream by the current to quiet water, collect in schools, spend their first year in lake water and as three-inch fingerlings eventually disappear into the Pacific.
Other salmon runs, like the Adams River run, are larger than that of the Horsefly. But the Horsefly, or the Quesnel-Horsefly, to give it the name the scientists use, was once one of the major runs of the whole immense Fraser River system.
The first salmon run that brought the Horsefly to the attention of the outside world was that of 1857. So many salmon churned up so much gravel in their spawning operation that year that they uncovered gold. Five men exploring up the Horsefly found free gold in the gravel near the lower limits of the spawning grounds; they picked up 100 ounces of gold nuggets in a week and started the great gold rush into the interior. More gold was found in other rivers than on the Horsefly, however, and the river, already notorious for the large numbers of big, black horseflies that gave it its name, gained further ill repute for not containing more gold.
The Horsefly next came in for considerable public attention in 1888. It occurred to some forgotten promoter that mining, which was now widespread not only in the wilderness around the Horsefly but in the Quesnel River below Quesnel Lake, would be easier if the flow of the river could be entirely stopped and the gold picked up at the miner's convenience from the dry gravel that would thus be left. The Golden River Quesnel Company Limited accordingly began a dam, 763 feet long and 18 feet high, at the outlet of Quesnel Lake. Fortunately for the salmon—if not for investors—the work proceeded so slowly that the runs of 1889, 1893 and 1897 went on their way up the Quesnel, past the dam to the Horsefly without being impeded in the slightest by the structure. But in 1898 the dam was finished. The flow of the Quesnel was completely blocked. The next great salmon run was due in 1901 and in 1900 the mining operation was abandoned.