字幕表 動画を再生する 英語字幕をプリント Somewhere in the world, a plant or animal species becomes extinct every day. And the pace at which our natural environments and ecosystems are being destroyed just keeps increasing. One creature under threat is the Lake Sturgeon. The Lake Sturgeon – is from a family of a prehistoric fish that have lived in North America’s freshwater lakes and rivers for millions of years. Many of Canada's Aboriginal peoples relied heavily on the Lake Sturgeon as a source of food. Early European settlers found new uses for the abundant Sturgeon, as fertilizer, livestock feed and even as a source of fuel. But today, its numbers have declined so drastically, the Lake Sturgeon is struggling for its survival. Lake Sturgeon populations are widespread throughout North America, with potential habitats ranging from western Alberta to the St. Lawrence in Quebec, and from southern Hudson Bay to the lower Mississippi. Today, the Lake Sturgeon is considered threatened in many US states and Canadian provinces, and is being considered for protection under Canada's Species at Risk Act. The Lake Sturgeon prefers cold water and is found in the near shore areas of large lakes and rivers. It is a bottom dweller, and feeds on leeches, clams, small fish and a variety of insects. The Lake Sturgeon is also known to travel long distances – sometimes over hundreds of kilometers - just to reach suitable spawning grounds. Lake Sturgeon can grow up to two and a half meters and can live to be 150 years old. However, unlike most fish, the Lake Sturgeon doesn’t begin spawning until it is quite old – 15 years for the males and 25 for the females. Once mature, they may spawn every three to four years. This means that despite its longevity, the Lake Sturgeon produces far less offspring than most other fishes. Over the past century, commercial fishing has caused significant declines in many Lake Sturgeon populations. For several decades they were heavily over-fished for their oil and later their caviar, which left much of the fish as waste. Lake Sturgeon populations are still recovering from the decimation of over-fishing. And because the Sturgeon only spawns every three to four years, it will take a great deal of time for the species to recover. In some places, the Lake Sturgeon is still fished beyond legal limits. However, strong education campaigns that promote catch and release have had a positive impact. More recently, the direct and indirect effects of hydro dams have become the most significant threat to this fish. Dams are formidable barriers that can stop the Lake Sturgeon from successfully reaching its spawning grounds. Hydro developers across Canada are currently working hard to find solutions to maintain access and natural flow patterns. Other threats to species recovery include: pollution, poaching and the introduction of invasive plant and animal species into the sturgeon’s natural habitat. Cottage developments are also adding new threats, as infilling, crib docks and manmade beaches reduce the amount and quality of good fish habitat in these once secluded natural areas. No one knows what will happen if we lose the Lake Sturgeon, or any other species. The Earth’s ecosystems are delicate and complex. Losing any species changes the natural dynamics and impacts all other parts of the ecosystem. Extinct is forever, so it is important to act now - because there is no second chance.
B2 中上級 カナダのチョウザメ湖を守る (Protecting Canada's Lake Sturgeon) 406 26 Bing-Je に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語