Tasmanian numbfish facts for kids
Quick facts for kids Tasmanian numbfish |
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Narcinidae
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Narcine
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N. tasmaniensis
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| Narcine tasmaniensis Richardson, 1841
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The Tasmanian numbfish (Narcine tasmaniensis) is a type of electric ray. It belongs to the Narcinidae family. This ray lives only in southeastern Australia. It's quite common. You can find it in shallow waters near the coast in the south. In the north, it lives in deeper waters. It likes to live in sandy or muddy places.
You can tell this ray apart by its special shape. It has a spade-shaped body with a long tail. The tail has skin folds on both sides. Its back is plain dark brown. The biggest Tasmanian numbfish found was about 47 centimeters (18.5 inches) long.
The Tasmanian numbfish lives on the bottom of the ocean and doesn't move around much. It mostly eats worms and small crabs or shrimp. Like all numbfishes, it can give a small electric shock. This shock helps it defend itself from other animals that might try to eat it. This ray gives live birth to its young. The babies grow inside the mother, getting food from a yolk. A mother can have one to eight babies at a time.
Fishermen often catch the Tasmanian numbfish by accident in their nets. This is called bycatch. However, its numbers seem to be doing well. The International Union for Conservation of Nature (IUCN) says it is a species of "Least Concern". This means it's not currently in danger.
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Meet the Tasmanian Numbfish
A Scottish naturalist named John Richardson first described the Tasmanian numbfish in 1841. He wrote about it in a science paper. He named it Narcine tasmaniensis because the first one he studied came from Port Arthur, Tasmania. That first ray was a female, about 36 centimeters (14 inches) long.
Local people sometimes called this ray "ground shark". Other names for it include electric ray, electric torpedo, and little numbfish. Scientists have studied its family tree using mitochondrial DNA. They found that the Tasmanian numbfish is a bit different from some other Narcine species.
What Does It Look Like?
The Tasmanian numbfish can grow to at least 47 centimeters (18.5 inches) long. Its body is shaped like a trowel, which is a small shovel. It has a short, blunt snout and curved edges on its body. Its eyes are medium-sized. Behind the eyes are smaller, round holes called spiracles. These help it breathe.
On each side of its head, it has two large electric organs. These are what produce the electric shock. There's a flap of skin between its nostrils. Its mouth is narrow and can stick out a lot. It has small, diamond-shaped teeth with pointy tips. These teeth are arranged in rows and stay visible even when its mouth is closed. It also has five pairs of gill slits under its body.
Its triangular pelvic fins are much longer than they are wide. Adult male rays have special parts called claspers. These extend past the pelvic fins. The tail is wide and flat. It's about a quarter longer than the body. The tail has clear skin folds on both sides. It has two dorsal fins (on its back) that are about the same size. The first dorsal fin starts above the back tips of the pelvic fins. The tail ends with a low caudal fin (tail fin). The top part of the tail fin is a bit angled, especially in adult males. The bottom part is rounded.
Its skin often has creases and is smooth. It doesn't have the rough scales that many sharks and rays have. The Tasmanian numbfish is dark brown on top. It gets lighter on its fins. Its underside is white. Sometimes, it has a few dark spots underneath. Many young rays also have a darker stripe down their back. They might also have darker spots on their body and near their dorsal fins.
Where Does It Live?
The Tasmanian numbfish is common off southeastern Australia. You can find it from Coffs Harbour in New South Wales all the way to Esperance Plains in Western Australia. It also lives all around Tasmania. Near Tasmania, it lives in coastal waters down to about 100 meters (330 feet) deep. This is on the continental shelf. In areas further north, it lives in deeper waters. There, it can be found at depths of 200 to 640 meters (660 to 2,100 feet). This is on the upper continental slope.
This ray lives on the bottom of the ocean. It likes sandy or muddy areas. Sometimes, you might find it near rocky reefs. Adult male and female rays seem to live separately from the younger rays.
Life and Habits
The Tasmanian numbfish is a quiet ray. It spends a lot of time buried and still in the sand or mud. It mainly eats worms, especially those from the Maldanidae family. It also eats crustaceans like amphipods, decapods (like crabs and shrimp), and tanaids. Sometimes, it might eat nematodes or sipunculids.
Young rays eat about equal amounts of worms and crustaceans. But as they get older, adults eat mostly worms. This change might be because older rays are better at finding and catching worms. Worms often burrow into the sand, making them harder to find than crustaceans.
Like other numbfishes, the Tasmanian numbfish can give a mild electric shock. This helps it protect itself. One of its predators is the broadnose sevengill shark. A type of tapeworm called Anthobothrium hickmani can also live as a parasite inside this ray.
Reproduction and Life Cycle
The Tasmanian numbfish gives live birth. The baby rays grow inside the mother. They get all their food from a yolk sac. Females usually have one to eight babies at a time. On average, they have eight. Newborn rays are about 9 to 12 centimeters (3.5 to 4.7 inches) long.
Male rays are ready to have babies when they are about 21 to 26 centimeters (8.3 to 10.2 inches) long. Female rays are ready when they are about 20 to 26 centimeters (7.9 to 10.2 inches) long.
Numbfish and Humans
Fishermen often catch the Tasmanian numbfish by accident. This happens in the South East Trawl Fishery in Australia. When caught, these rays are usually thrown back into the ocean. We don't know exactly how many survive, but it's probably a lot.
Even though numbfish can give an electric shock, it's not very strong. It's much weaker than the shocks from other electric rays. So, they are not considered very dangerous to humans. This species does not seem to be in danger from human activities. Because of this, the International Union for Conservation of Nature (IUCN) has listed it as "Least Concern".
