American paddlefish facts for kids
Quick facts for kids American paddlefish |
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| American paddlefish (facing left) | |
| Conservation status | |
| Scientific classification | |
| Genus: |
Polyodon
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| Species: |
spathula
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| Synonyms | |
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Genus
Spatularia Shaw 1804 non Haworth 1821 non van Deventer 1904 non Mehely 1935
Platirostra LeSueur 1818 Megarhinus Rafinesque 1820 non Schoenherr 1833 nomen nudum non Robineau-Desvoidy 1827 Proceros Rafinesque 1820 non Quatrefages 1845 Species
Squalus spathulus Walbaum 1792
Megarhinus paradoxus Rafinesque 1820 Platirostra edentula Lesueur 1818</ Polyodon feuille Lacépède 1797 Polyodon folius Bloch & Schneider 1801 Proceros maculatus Rafinesque 1820 Spatularia reticulata Shaw 1804 Proceros vittatus Rafinesque 1820 Accipenser lagenarius (sic) Rafinesque 1820 ?Polyodon pristis Rafinesque 1818 |
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The American paddlefish (Polyodon spathula) is a unique freshwater fish. It is closely related to sturgeons. This fish has been around for a very long time, with fossils dating back over 125 million years!
People call it by many names, like Mississippi paddlefish or spoonbill. It is the only living species in its family, Polyodontidae. Another paddlefish, the Chinese paddlefish, recently became extinct.
The American paddlefish is often called a "primitive fish." This is because it still has features from its ancient ancestors. For example, its skeleton is mostly cartilage, not bone. It also has a long, paddle-shaped snout, called a rostrum, which can be almost one-third of its body length.
This fish is special because it has tens of thousands of tiny sensors on its snout and head. These sensors help it find its main food source: tiny water creatures called zooplankton.
American paddlefish used to live freely throughout the Mississippi River basin. This included large rivers, braided channels, and oxbow lakes. They even lived in parts of the Great Lakes in Canada.
Sadly, their numbers have dropped a lot. This is mainly due to too much overfishing, losing their homes (habitat destruction), and pollution. Poaching (illegal fishing) also hurts them, especially because people want their caviar.
Today, American paddlefish are found in 22 states in the U.S. They are protected by state, federal, and international laws.
Contents
About the American Paddlefish
American paddlefish are related to sturgeons. They belong to an ancient group of ray-finned fish called Acipenseriformes. This group has a long fossil record, showing they first appeared about 125 million years ago.
The name Polyodon comes from Greek words meaning "many toothed." This is interesting because adult American paddlefish actually have no teeth! The name probably refers to their comb-like gill rakers. The word Spathula refers to their long, paddle-shaped snout.
American paddlefish are often called "primitive fish." This is because they have kept some features from their very old ancestors. For example, their skeleton is mostly cartilage. They also have a deeply forked tail, similar to sharks, even though they are not closely related to sharks.
The Chinese paddlefish was a relative that recently became extinct. It was different from the American paddlefish. It had a narrower, sword-like snout and ate small fish and crustaceans. The American paddlefish mainly eats tiny zooplankton.
What They Look Like
American paddlefish are some of the biggest and longest-living freshwater fish in North America. They can grow to about 1.5 m (4.9 ft) long and weigh around 27 kg (60 lb). Some can live for over thirty years! Females usually live longer and grow larger than males.
These fish have smooth skin and a body shape similar to a shark. Their eyes are small and point to the sides. They have a large mouth and a flat, paddle-shaped snout (rostrum). This rostrum can be about one-third of their total body length.
When they are very young, American paddlefish do not have a rostrum. It starts to grow soon after they hatch. The rostrum is part of their skull, not their jaws. They also have a deeply forked tail and are usually bluish-gray to black on top, with a whitish belly.
How They Eat and Sense Their World
For a long time, scientists wondered what the paddlefish's rostrum was for. Some thought it helped them dig in the mud or balance. But in 1993, new studies showed something amazing. The rostrum is covered with thousands of tiny sensors.
These sensors are like the ones sharks and rays have. They are called electroreceptors. American paddlefish use them to find plankton by detecting weak electrical fields. These fields are created by the plankton's movements.
When a paddlefish finds a group of zooplankton, it swims forward with its mouth wide open. It filters the water through its gill rakers to catch the tiny prey. This way of eating is called ram suspension-feeding. The electroreceptors may also help them avoid obstacles.
American paddlefish have small eyes and do not rely much on sight. Their electroreceptors are their main way of sensing food. Even if a paddlefish has a damaged rostrum, it can still find food and stay healthy. This is because they also have sensory pores on their head and gill flaps.
Reproduction and Life Cycle
American paddlefish live a long time, but they start having babies later in life. Females usually begin spawning when they are 7 to 10 years old. Some might wait until they are 16 to 18 years old. Females do not spawn every year; they usually spawn every second or third year. Males start spawning earlier, around age 7, and can do so every year or every other year.
They travel upstream to spawn in early spring. They need gravel bars that are free of mud. These areas must be covered by rising river water from melting snow and spring rains. For them to spawn, three things must happen:
- The water temperature must be between 55 to 60 °F (13 to 16 °C).
- The days must be getting longer, which happens in spring.
- The river must have the right rise and flow.
Historically, these perfect conditions only happened every 4 or 5 years, so paddlefish did not spawn every year.
American paddlefish are "broadcast spawners." This means the females release their eggs into the water over rocks or gravel. At the same time, males release their sperm. The eggs become sticky and attach to the river bottom.
The eggs hatch into larval fish in about seven days if the water is around 60 °F (16 °C). These tiny fish then float downstream to calmer areas. There, they start eating zooplankton.
Young paddlefish are not strong swimmers, so they can be easily caught by predators. Growing fast in their first year is very important for them. Baby fish, called fry, can grow about 1 in (2.5 cm) per week. By late July, they are about 5–6 in (13–15 cm) long. Their growth depends on how much food is available.
Interestingly, in 2020, scientists successfully crossbred Russian sturgeon eggs with American paddlefish sperm. This created a new hybrid fish called "sturddlefish." This was the first time fish from such different groups were successfully crossbred!
Where They Live
American paddlefish are very mobile and live well in rivers. They can be found in many river habitats across the Mississippi Valley. They prefer deeper, slow-moving areas like side channels, oxbow lakes, and areas below dams. They have been known to travel over 2,000 mi (3,200 km) in a river system.
Historically, they lived throughout the Mississippi River Basin. This included rivers from the northwest to the northeast, and from the headwaters south to the mouth of the Mississippi. They disappeared from states like New York, Maryland, and Pennsylvania. They also vanished from parts of the Great Lakes region.
However, some states have started programs to reintroduce them. For example, Pennsylvania began stocking hatchery-raised paddlefish in the Ohio and Allegheny rivers in 1991. New York also started stocking programs. While adult fish have been found, there is no clear sign of them reproducing naturally in these areas yet.
Today, American paddlefish are found in 22 states in the U.S. They are protected by state and federal laws. Some states allow sport or commercial fishing for them under strict rules.
People and Paddlefish
Raising Paddlefish
People started raising American paddlefish artificially in the 1960s. This was mainly to help with sport fishing. But soon, people realized paddlefish were also valuable for their meat and roe (eggs), which can be made into caviar.
Raising them artificially means getting adult fish from the wild. These fish are given a hormone to help them spawn. A female can produce anywhere from 70,000 to 300,000 eggs! There are different ways to collect the eggs from the female fish. Scientists make sure the eggs are ready before collecting them.
Once the eggs are collected, they are mixed with sperm from male paddlefish. The fertilized eggs are sticky and sink to the bottom. They are then put into special containers to hatch, which usually takes 5 to 12 days.
Global Market
Thanks to new technology, there is now a worldwide market for raising American paddlefish. In 1970, paddlefish were sent from the U.S. to Europe and Asia. For example, thousands of young paddlefish were sent to the former Soviet Union for aquaculture (fish farming).
They successfully reproduced there, and young paddlefish were then sent to other countries like Romania and Hungary. Today, American paddlefish are raised in Ukraine, Germany, Austria, and Bulgaria.
China also imports millions of fertilized paddlefish eggs and young fish every year from Russia and the United States. Some are raised in ponds with carp and sold to restaurants. Others are raised to produce caviar. China has even sent American paddlefish to Cuba for caviar farming.
Sport Fishing
American paddlefish are a popular sport fish in places where their populations are healthy enough. In areas where their numbers are low, state and federal programs release fish to keep the sport alive.
Since paddlefish are filter-feeders, they do not bite on bait or lures. Instead, they are caught by "snagging." This means using a hook to snag the fish as it swims by.
Many states have records for the largest paddlefish caught. In Kansas, a paddlefish weighing 144 lb (65 kg) was snagged in 2004. The biggest American paddlefish ever recorded was caught in Iowa in 1916. It was 85 in (2.2 m) long and weighed an estimated 198 lb (90 kg)!
Why Their Numbers Are Declining
Overfishing and Habitat Loss
The number of American paddlefish has dropped a lot. The main reasons are too much fishing and the destruction of their homes. In 2004, they were listed as Vulnerable on the IUCN Red List of Threatened Species. This means their population could shrink by at least 30% in the next 10 years.
Paddlefish need large, free-flowing rivers with many channels, backwater areas, and oxbow lakes. These places must have lots of zooplankton for food and gravel bars for spawning.
Building dams on rivers, like the Missouri River, has trapped many paddlefish. Dams block their journey upstream to their spawning grounds. Changes to rivers, like making them narrower, also destroy important spawning and nursery habitats. Because of this, many paddlefish populations behind dams cannot survive on their own and need to be restocked.
Zebra Mussels
Zebra mussels are an invasive species that are also harming paddlefish. These mussels have spread in the Mississippi River and Great Lakes. Zebra mussels are filter feeders, just like paddlefish. They eat huge amounts of phytoplankton and zooplankton from the water. This means less food is available for paddlefish and other native animals.
Zebra mussels reproduce very quickly. Even though some animals eat them, it has not been enough to control their populations.
Illegal Fishing
Poaching (illegal fishing) has also contributed to the decline of American paddlefish. This is especially true where there is a high demand for caviar. Since the 1980s, there have been limits on importing expensive beluga caviar from the Caspian Sea. This made people look for other sources of caviar, like American sturgeon and paddlefish.
The roe (eggs) of American paddlefish can be made into caviar that tastes and looks similar to some sturgeon caviar. Because of this, some illegally caught paddlefish roe has been sold as more expensive Caspian Sea caviar.
Laws are very strict about catching paddlefish and illegally selling their roe. People who break these laws can face big fines and even prison time. Paddlefish are also protected by CITES, an international agreement that controls the trade of endangered animals and plants.
See also
In Spanish: Pez espátula para niños
