When dams affect fish populations, they also affect the people and industries that depend on those fish. By changing the timing and amount of fish coming through different sections of the river, dams can detrimentally alter local peoples fishing practices. A current example of this is threatening to occur on the Mekong River with the proposed construction of a dam on the Hoo Shong waterway. Currently the major fish of the Mekong fishery travel upstream through this critical waterway that is the only natural unobstructed waterway around Khone Falls on the Mekong River. The ability of the fish to make it through this passageway is crucial to the lives of village people located further north who are dependent on the fish for food and income. A recent agricultural census found the people in provinces bordering the Mekong received between 27 and 78% of their protein from the fish that routinely traveled up the Hoo Shang, indicating even further the importance in keeping the waterway unobstructed with no dam building.
Besides hurting regional food supplies, the reductions in fish population dams cause equate to a high economic cost as well, sometimes reducing numbers to the point the regional fishing industry is severely harmed or destroyed. Dams on the Missouri River led to major fish losses in the early 1900s, going from a catch of 680 tons in 1894 to 122 tons in 1963, which obviously equated to great profit reductions. One of the now most dammed rivers in North America, the Columbia River lost $6.5 billion from its fishing industry between 1960 and 1980 due to its many dams' effects on fish. In addition to sheer profit loss, other expenses arise for the fishing industry, such as the cost of stocking rivers with hatchery-raised fish since wild stocks are so low, in an attempt to at least maintain a fish population for the recreational side of the industry. The video below discusses this issue in the context of Tennessee rivers.
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