Dinosaurs of the Deep Background Reading for Students




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Dinosaurs of the Deep - Background Reading for Students



Evolution

Fish arose over 500 million years ago, sturgeon first appeared approximately 175 million years ago, and today these dinosaurs of the deep remain relatively unchanged. While many of the Earth’s first fish have gone extinct, and many more have evolved to become the first vertebrates, sturgeon have remained relatively unchanged. These characteristics include: a cartilaginous skeleton, fine-grained skin with scale-like plates (denticles), torpedo shape, upturned tail fin, mouth set far back on the underside of the head, a blunt nose, and bony scutes. Sturgeon are well-adapted bottom feeders. They use their protractible tube mouth like a vacuum to suck up whatever they come across on the riverbottom. Because sturgeon spend much of their life in the dark depths, their eyes are very small and their eyesight poor. To compensate, they have developed highly sensitive whiskers or barbels to help locate prey.
Sturgeon are anadromous fish, they can spend all or part of their adult! lifecycle in salt water returning to fresh water to spawn. Historically, white sturgeon on the lower Columbia River spent much of their life in the ocean, feeding in the rich marine environment, and then returning to the rivers to spawn. Scientists believe that white sturgeon on the upper Columbia River did not historically migrate to the ocean like the sturgeon of the lower Columbia. However, scientists do believe that their movements have been greatly affected within the upper Columbia Basin by the development of numerous hydroelectric dams, and today they are effectively a landlocked species spending no time in the ocean.

Distribution

There are 29 species of sturgeon found throughout the world. All of these species are found in the Northern Hemisphere including Europe, Asia and North America. Of the 9 species found in North America, 2 are located on the West Coast. These include both the green sturgeon (Acipenser medirostris) and the white sturgeon (Acipenser transmontanus). Acipenser transmontanus, or “sturgeon beyond the mountains”, are found in 3 major drainages, California’s Sacramento River, the Columbia River, and the Fraser River. In British Columbia, spawning populations of white sturgeon occur in three rivers: the Fraser, Nechako, and Columbia / Kootenay.


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