The eel-tailed catfish, Tandanus tandanus, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

 (order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Siluriformes) of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Plotosidae. This fish is also known as dewfish, freshwater catfish, jewfish, and tandan.

Distribution

This species is a freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 native to the Murray

Murray River

The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...

-Darling

Darling River

The Darling River is the third longest river in Australia, measuring from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales. Including its longest contiguous tributaries it is long, making it the longest river system in Australia.The...

 river system of eastern Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. The scientific name for eel-tailed catfish comes from an aboriginal name for the fish - Tandan - which Major Mitchell recorded on his 1832 expedition.

Description

Eel-tailed catfish commonly grow to about 50.0 centimetres (19.7 in) and weigh about 1.8 kilograms (4.0 lb). Fish of this species may grow up to about 90.0 cm (35.4 in) and weigh up to 6.0 kg (13.2 lb). Eel-tailed catfish may live up to about 8 years.

Eel-tailed catfish have large head with thick and fleshy lips and tubular nostrils. The skin is tough and smooth. Body coloration in adults vary from olive-green to brown, black or purplish on their backs and white on the underside. A downturned mouth with fleshy lips surrounded by a number of barbels

Barbel (anatomy)

A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

 assist them with feeding. They are a solid, almost cylindrical, elongate fish, with the posterior half of their body tapering into a pointed eel-like tail. A continuous fin margin surrounds this tapering posterior half of the body. Their eyes are small.

Ecology

The eel-tailed catfish inhabits slow moving streams, lakes and ponds with fringing vegetation. It swims close to the sand or gravel bottoms. This species is more abundant in lakes than in flowing water. Though they are usually solitary, juveniles may form aggregations. The eel-tailed catfish is found in most freshwater habitats of the Murray-Darling river system except for the upland, sub-alpine and alpine headwaters of southern tributaries. It is also present in speciated but undescribed forms in several east coast systems in northern New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

 due to natural river capture

River capture

Stream capture, river capture, or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream...

 events.

Eel-tailed catfish feed on insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e, prawn

Prawn

Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...

s, crayfish

Crayfish

Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...

, mollusks, and small fishes. The eel-tailed catfish is host for a number of intestinal parasite

Intestinal parasite

Intestinal parasites are parasites that populate the gastro-intestinal tract in humans and other animals. They can live throughout the body, but most prefer the intestinal wall. Means of exposure include: ingestion of undercooked meat, drinking infected water, and skin absorption...

s including cestodes and nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s.

Eel-tailed catfish spawn in spring and midsummer, when the water temperature increases to between 20–24°C (68–75°F. The nest is built about one or two weeks before spawning. They build large nests up to a metre in diameter with small stones and gravel, within which the eggs are laid. One parent, sometimes both, guard the eggs until they hatch.

Conservation

The Murray-Darling populations of eel-tailed catfish has declined significantly over recent decades. Most populations in the southern half of the Murray-Darling river system are extinct or nearly so.

There are suggestions that introduced carp

Common carp

The Common carp is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia. The wild populations are considered vulnerable to extinction, but the species has also been domesticated and introduced into environments worldwide, and is often considered an invasive...

, with similar feeding habitats, directly compete with eel-tailed catfish, to the detriment of the catfish. Severe siltation also probably severely impacts upon the species spawning by smothering the rocks and pebbles they use to build nests.

Fortunately, populations in several rivers and impoundments in the northern half of the Murray-Darling appear secure for now. Interestingly, the species does well in the upland reaches of these northern Murray-Darling rivers; this is in contrast to its absence from the upland reaches of southern Murray-Darling rivers, where water temperatures are cooler.