Paddlefish

Q.

What species found in the Ohio River that can weigh almost 200 pounds, looks like a shark with a Pinocchio nose, and has been around since 50 million years before the dinosaurs?


A.

Polyodon spathula: The paddlefish Paddlefish are one of the oldest fishes, with fossil records dating their first appearance at 300 to 400 million years ago.[6]

paddlefish

So what's with the big nose?

A paddlefish's paddle is technically called a rostrum. After experimenting with the paddlefish, University of Missouri, St. Louis researcher Lon A. Wilkens concluded that the paddle acts as a highly developed antenna primarily used to detect tiny plankton on which the paddlefish feeds.[1]

Thousands of tiny pores penetrate the skin on the upper and lower surfaces of the paddle to the top of the head and tips of the gill covers. In all, they occupy nearly half the skin surface of the fish. These pores function as electro-receptors.[1]

These receptors are amazingly sensitive and can respond to very small electrical fields like an antenna. Plankton, such as the water flea (Daphnia), have been found to emit weak electrical signals. Exactly how a paddlefish translates the detection of weak electrical signals into accurate feeding strikes on tiny plankton is unknown. But, without its antenna, the paddlefish would probably not survive as a planktivore in its murky aquatic environment. The paddle and electro-receptors allow the paddlefish to feed with little competition from other fish that feed primarily by sight.[1]

Before 1900, paddlefish were a common component of fish communities in Mississippi River and the large rivers in its drainage basin including the Ohio River. Currently, however, paddlefish have been lost from four states and Canada, and half the states within the paddlefish's range list it as endangered, threatened, or a species of special concern.[6] Many state and federal agencies are working to restore paddlefish populations in its native range.

The decline of the paddlefish has been attributed to:

  • Habitat Alteration: Construction of dams on rivers has especially affected paddlefish by altering traditional river habitats and disrupting spawning migrations and other movements.
  • Overharvest of the fish, particularly for its eggs (roe)
  • Pollution has also played a role in their decline. [6]

Because of the decline of the European sturgeon, North American paddlefish and sturgeon have been subject to increasing harvest to supply eggs to meet the worldwide demand for caviar. Paddlefish eggs are important to the commercial caviar business. In fact, much of the caviar that is sold as sturgeon roe is actually paddlefish roe. Some paddlefish roe is caught and sold legally, others are not.[5]

Paddlefish cannot be caught by traditional fishing methods because of their feeding habits. Most paddlefish are caught accidentally or snagged by anglers.[2] If you happen to catch a paddlefish, it is best to get it back into the water as soon as possible. But afterward you might want to contact Patrick Barry. Barry is a Penn State graduate student researcher trying to discover what is happening to paddlefish in the rivers near Pittsburgh. To help his research, Barry is posting bright yellow signs this spring at boat launches along the Ohio River, at local fishing tackle shops and anywhere else folks who enjoy the river gather. "Have You Seen This Fish?" they ask in bold letters. Barry would like to know where, when and how you caught your fish. You can contact him at paddlefish@psu.edu.[3]

PADDLEFISH STATS AND FACTS

Identification

Without their long snout they would resemble sharks - deeply forked tail - gray in color

Size & Weight

Commonly reaching 5 feet or more in length and 60 pounds in weight.The largest paddlefish on record was caught in Iowa and weighed 198 pounds. [6]

Life-span

Some studies have estimated that paddlefish may live in excess of 50 years. [6]

Distribution

Native to Lake Erie, the Ohio River and its tributaries

Habitat

They frequent many types of riverine habitats but often seek out deeper, low current areas such as side channels, backwaters, oxbow and other river-lakes, and tailwaters below dams. Paddlefish are highly mobile and have been observed to move more than 200 miles in a river system. [6]

Feeding

Filter feeders similar to giant baleen whales. Paddlefish have extensive comb-like gill rakers to filter the water and capture tiny crustaceans and insect larvae that drift as plankton in the water. Like a whale, a paddlefish swims with its mouth open wide so it can filter plankton from large quantities of waterPaddlefish less than 7 or 8 inches long do not have well developed gill rakers and cannot strain mass quantities of plankton from the water. Instead, small paddlefish feed by capturing individual plankton, one at a time. [1]

Reproduction

Paddlefish take a long time to become mature and capable of spawning. Paddlefish males are ready at seven years and about 40 inches long. Females take nine or 10 years, and are about 42 inches long when they first spawn. [3]Paddlefish spawn in the spring during periods of high flow. The female scatters eggs over submerged gravel and cobble bars. The young hatch and drift down stream to deeper pools with slow water. [2]

Etymology

Genus: Polydon: from a Greek word meaning "many tooth", refers to their gill rakers Species: spathula is Latin for "spatula" or "blade," in reference to the fish's paddle or rostrum. [4]

REFERENCES

[1] Missouri Conservationist On-line http://www.conservation.state.mo.us/conmag/2001/01/30.htm
[2] Ohio Department of Natural Resources http://www.dnr.state.oh.us/wildlife/1newsite/Fishing/aquanotes-fishid/padlfish.htm
[3] Penn State news release February 6, 2003 http://aginfo.psu.edu/News/february03/paddle.html
[4] Texas Parks & Wildlife http://www.tpwd.state.tx.us/fish/infish/species/pad/pad.htm
[5] U. S. Fish & Wildlife http://orve.fws.gov/paddlefish.html
[6] U. S. Geological Survey http://www.umesc.usgs.gov/aquatic/fish/paddlefish/risk.html