Morphology and Behavior
Polyodon spathula (Paddlefish) are an intriguing and strange freshwater fish. Their long nose, or rostrum, is a distinct feature. This rostrum is formed after hatching and is covered in sensory pores. Another distinct feature is a long operculum flap which may aid in protecting the gills while feeding. Their skin is smooth and isn’t scaled, resembling that of a shark. Like sharks, they have a cartilaginous skeleton that consists mostly of a spinal cord and lack bones. They have a tail that is heterocercal and small eyes placed close to the mouth. Paddlefish can reach up to 5 feet in length and weigh over 60 pounds (Jennings, 2000).
Paddlefish feed by swimming with their mouths open, usually near the surface of the water. They travel long distances in search of food and for breeding. Paddlefish are long lived, and do not reach sexual maturity until 7-10 years of age. Spawning typically occurs in late spring during the correct conditions. Paddlefish migrate upstream in search of correct conditions for water flow, temperature, length of day, and correct substrate. Without all of these conditions, Paddlefish will not spawn, sometimes going 3 years between events. When a spawn does occur, males and females broadcast sperm and eggs over a gravel bed. Fertilization occurs externally and the eggs wash downstream to deeper pools (Jennings 2000).
Conservation Concerns
Paddlefish numbers have been gradually declining due to pollution and other human factors. One major concern is in breeding. Since Paddlefish are so picky about breeding conditions, it is of the utmost importance that breeding sites be maintained. The manipulation of riverbanks, addition of dams, and other practices affecting river level can prevent breeding. Another factor that makes their reproduction slower is old age to reach sexual maturity. Their feeding behaviors can put them at risk as well. Swimming near the surface puts them in danger of being struck and killed by boats. Finally, people exploited them in the past for meat and caviar. The meat is desirable due to the lack of bones. The Roe (eggs) are popular for caviar due to the mild flavor and large number of eggs per fish (Jennings, 2000).
Commercial Market
Paddlefish are commonly farmed. The main motivation for farming is for caviar. Their caviar can be sold for as much as $35 and ounce and females can produce about 20 pounds of caviar ($11,200 per fish). Their meat is sold as a byproduct, though it is highly sought after. Paddlefish farming is appealing to many fish farmers. In addition to improving water quality, they do not require supplemental feeding. Farm ponds are often stocked and left to sit for 7 years until females reach maturity (Jennings, 2000).
Paddlefish Caviar
For more information on this intriguing fish, check out this article!
https://pubs.er.usgs.gov/publication/1017141
Works Cited
Pictures
https://www.outdoorlife.com/articles/fishing/2015/03/egg-takers-harvesting-americas-paddlefish-caviar/
Information
Jennings, C. A., & Zigler, S. J. (2000). Ecology and biology of paddlefish in North America: historical perspectives, management approaches, and research priorities. Reviews in Fish Biology and Fisheries, 10(2), 15.