The paddlefish is a large, fresh water fish that is unique due to its long snout that is shaped like the oar or paddle of a boat. It belongs to the Polyodontidae family with just two known species, the American and the Chinese paddlefish. The Chinese hasn't been seen in years and is believed to be extinct, however. The paddlefish usually lives in large rivers such as the Mississippi. Despite its large size it is a gentle fish, feeding on plankton, and has protected status in many areas where it is still found.
The paddlefish has gray smooth skin with a body shaped like a shark's, and it can grow to a length of 5 to 7 feet (1.5 to 2.1 m) and can weigh up to 200 pounds (91 kg). One of its most noticeable features is its enormous, wide opening mouth, and the other is the paddle-like snout for which it is named. The paddle is usually about a third of the length of the body, and protrudes above the mouth.
The habitat of the paddlefish occupies a large part of the United States in North America, stretching from the eastern states as far west as the state of Montana. It lives mainly in large rivers like the Missouri and Mississippi, as well as lakes and river basins. It is an ancient species that is believed to have been in the area for millions of years, according to fossil records. For some time it was a popular target of sport fishermen, and is now considered endangered in many regions.
The paddlefish's diet consists mainly of plankton, which is made up of tiny plants and animals that float in the water. The fish swims with its mouth wide open, filtering plankton from the water with structures called gill rakers located on the gill arches inside the mouth. Occasionally tiny fish and insects are also filtered out of the water and consumed.
There are electrosensory receptors all over the paddle shaped snout that help the paddlefish sense objects near it. Scientists believe that the fish uses them for navigation, and to help with finding food. The receptors can particularly important for assisting the fish as it finds its way to different areas of the river.
Spawning usually occurs in late May or early June when the river's water level is high. The eggs are sticky and tend to stick to the gravel of the riverbed and hatch in about seven days. The tiny babies are only about 1 inch (2.5 cm) long but they grow very quickly. Paddlefish can live as long as 50 years in the right conditions.