The PADDLE FISH

Paddlefish (family Polyodontidae) are primitive Chondrostean ray-finned fishes. The paddlefish can be distinguished by its large mouth and its elongated snout called a rostrum (bill). These spatula-like snouts comprise half the length of their entire body. There are only two extant species of these fish: the Chinese and the American paddlefish. The American species is Missouri's State Aquatic Animal.

These fish are not closely related to sharks, but they do have some body parts that resemble those of sharks such as their skeletons, primarily composed of cartilage, and deeply forked heterocercal tail fins.

In some areas, paddlefish are referred to as "Spoonbill", "Spoonies" or "Spoonbill Catfish". Paddlefish are also extremely oily. Mounted specimens occasionally leak an oily substance.

The American paddlefish, Polyodon spathula, also called the Mississippi paddlefish or spoonbill, lives in slow-flowing waters of the Mississippi River drainage system. It appears to have been extirpated from Lake Erie and its tributaries. They are closely related to the sturgeons. This large Chondrostian freshwater fish may grow to 220 cm (7 feet) and weigh up to 100 kg (220 pounds). The paddlefish takes its common and scientific names from its distinctive snout, which is greatly elongated and flattened into a paddle shape. The American paddlefish is believed to use sensitive electroreceptors on its paddle to detect prey, as well as to navigate while migrating to spawning sites. The paddlefish feeds primarily on zooplankton but also feeds on crustaceans and bivalves.

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".

The rostrum contains receptors in its rostrum 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, it has been observed that fish with severely damaged or missing rostrums are able to feed and are 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. After hatching, the young are swept downstream and grow to adulthood in deep freshwater pools.

Once common throughout the Midwest, overfishing and habitat changes have caused major population declines; both the meat and roe of the paddlefish are desirable as food. Dams and other barriers can prevent the fish from recolonizing places where they once occurred and can deny them access to important critical habitats such as spawning areas. Until about 1900, the paddlefish was also found in the Lake Erie and in river systems tributary thereto in the US and Canada. Invasive species such as zebra mussels have reduced the number of zooplankton in the Great Lakes to such low levels that any hypothetical reintroduction program would seem likely to fail. Recently, paddlefish were spotted in the Danube river. It has not been determined whether these fished escaped from Romanian or Bulgarian fish farms during the 2006 European floods, or whether they were let into the Danube earlier and matured in the river.

The American paddlefish remains a popular sport fish in those parts of its range where populations are sufficient to allow harvesting. Since they are filter-feeders, paddlefish will not accept bait or lures and must be caught by snagging. Several states, including Missouri, have enacted stocking programs for these fish in reservoirs where the resident populations were low or nonexistent, or in areas where historical populations are no longer naturally sustainable. Paddle fish are killed for their eggs which are used as caviar.

Polyodon spathula is one of two living species of Paddlefish.

During the last century, paddlefish and sturgeon have stimulated the world stock trades with their eggs (roe), called caviar. Paddlefish and sturgeon are two of the most important fish for freshwater caviar. Paddlefish take many years before they are able to spawn. A female may take 9 to 10 years, when they are about 42 inches long, and males 7 years old and 40 inches long are able to spawn. When able to spawn, the female releases adhesive eggs randomly over the water bottom and abandons them. They are capable of producing over one-half million eggs a year, but they may not spawn every year.

Due to the value of their eggs, paddlefish are a constant target for poachers, and they are subsequently a protected resource over a large part of their range. Additionally, in many of the 22 states that paddlefish reside, habitat destruction is causing their numbers to decrease more rapidly. Paddlefish need free flowing rivers that have shallow pools with sandy, rocky bottoms. These types of areas are perfect for their spawning. Water must also be at the right temperature for the fish to be capable of spawning. Since today's rivers are constantly being modified by the construction of dams, dredging, and excessive water removal for farming purposes, these types of areas are hard for the paddlefish to locate.

In some areas, free flowing lakes with reservoirs are able to provide paddlefish with the right breeding habitat. One such area is the Missouri River-Lake Sakakawea system in North Dakota. This area is capable of producing good paddlefish numbers because it is a free flowing system with many good areas for paddlefish to spawn. Fishing for paddlefish in violation of local fishing regulations in some states is a felony.

Source : Wikipedia