Physical Characteristics
Early investigators once thought that paddlefishes used their snouts to dig vegetation from the bottom of lakes and rivers. In fact, they feed by filtering out zooplankton from the water, using filaments on their gill arches called gill rakers, and in this respect appear similar to the basking shark.
As in many of the distantly related shark class, the paddlefish's rostrum contains electroreceptors that can detect weak electrical fields, suggesting that they use their rostrum as an antenna to detect zooplankton. Even though the rostrum seems to help the fish feed, fish with severely damaged or missing rostrums are able to feed and appear to be just as healthy as other fish with them intact.
The rostrum also helps the fish to feed by acting as a stabilizer. As the fish moves through the water with its mouth open, the rostrum creates lift, much like a wing of an airplane. This helps the fish by keeping its head in a steady position and helps it keep from diving to the bottom.
Paddlefish lay their eggs in midstream over bare rocks or gravel. The eggs are adhesive and stick to the rocky substrate. The young are swept downstream after hatching and grow to adulthood in deep freshwater pools.
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