It would not be inaccurate to think of paddlefish as "living fossils.Researchers have found that Japanese sea catfish, like this one, have evolved sensors on their whiskers that can detect slight changes in water acidity to help the fish find prey in the dark. The Polyodontidae family of fish goes back to the Early Cretaceous, 120 to 125 million years ago, about the same time that flowering plants (angiosperms) appeared on Earth. The other four disappeared long, long ago and are known only from fossil evidence. In addition to our paddlefish, only five other species of paddlefishes are known: One is the recently extinct Chinese paddlefish. Unlike our plankton-feeding paddlefish, the Chinese paddlefish was a fish-eater. No one has seen a living Chinese paddlefish since 2003. Attempts to propagate the species artificially (as we do with North America's paddlefish) were unsuccessful. As late as the 1970s, annual harvest of the Chinese paddlefish was 25 tons. Dams on the rivers prevented them from doing this, just as dams prevent our paddlefish from moving up and down stream channels. Like salmon, adults of that species needed to be able to move from the sea upstream into freshwater to spawn. It was native to the Yangtze and Yellow River systems in China (huge rivers that are similar to our Mississippi and Missouri rivers). Sadly, the paddlefish's closest relative, the Chinese paddlefish, has recently been declared extinct. The constant grazing of these fish on tiny aquatic organisms helps to keep their populations in check paddlefish and their eggs and fry provide food for other aquatic predators.
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