Summary: | The four nations of Salmon World have existed for 10,000 years. Since the end of the last Ice Age, salmon established naturally substantial populations and prospered in four large regions of the earth: (1) the European side of the North Atlantic; (2) the North American side of the North Atlantic; (3) the Asian side of the North Pacific; and (4) the North American side of the North Pacific. Taxonomically, salmon are categorized into two groups: (1) the several species comprising the Pacific salmon; or (2) the single species of Atlantic salmon. Anadromous brown trout (sea trout) share similar life history with Atlantic salmon and are affected by the same factors as Atlantic salmon. All seven species of Pacific salmon on both sides of the North Pacific Ocean have declined substantially from historic levels, but large runs still occur in northern British Columbia, Yukon, Alaska, and the Far East of Russia. Atlantic salmon on both sides of the North Atlantic Ocean have declined even more precipitously than have North Pacific Ocean salmon. The largest (though small by historic standards) remaining runs of Atlantic salmon occur in the rivers along the Atlantic coasts of northern Canada and northern Scandinavia; however, the worldwide number of Atlantic salmon is large, perhaps even larger than at any time in history, because massive numbers of Atlantic salmon are raised in aquacultural facilities. Hatchery production and release of Pacific salmon has been used to maintain some runs in the southern region of the range (e.g., Japan, Korea, California, Oregon, and Washington). In California, Oregon, Washington, Idaho, and southern British Columbia, runs have been depleted by loss of spawning and rearing habitat, a history of over-fishing, dam construction and operation, water withdrawal for irrigation and industrial cooling, competition with hatchery-produced salmon, competition with various non-indigenous fish species, predation by marine mammals and birds, and climatic and oceanic shifts. Runs in the northern half of the range (e.g., Russian Far East, Alaska, Yukon, and northern British Columbia) are in better condition, a situation likely to continue for the foreseeable future. The northern runs have been relatively abundant since the mid 1970s, but will likely decline somewhat for the next several decades because ocean conditions in the North Pacific tend to shift on a several-decade time cycle. Southern runs should be relatively better (though low by historic standards) for the next several decades, but decline again when ocean conditions shift. In the western region of the contiguous United States, billions of dollars have been spent in a so-far failed attempt to reverse the long-term decline of wild Pacific salmon. Of the four nations of Salmon World, it appears probable that western North America will emulate the other three: extirpated or much reduced runs in the southern half of the range; runs closer to historic levels in the northern half of the range (British Columbia northward).
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