Procambarus clarkii – Red Swamp Crawfish

Procambarus clarkii – Red Swamp Crawfish

Procambarus clarkii was first described in 1854 by Charles Frédéric Girard. They are part of the family Cambaridae. This family is originally from Central and North America. The family includes about 16 genera and 161 species.

Description

With a maximum length (without scissors) of 12 centimeters, Procambarus clarkii is medium in size. In the wild, it is coloured dark red to black. White to red dots are visible on top. These dots develop into spines on the scissors.

Various varieties that do not occur in the wild have now been bred in the aquarium trade. They are commercially available in white, blue, orange and bright red.

Gender Distinction

Especially during the mating season, the difference between males and females is clearly visible. The male then gets a kind of hooks on the second and third walking legs. Outside the mating season, you can tell the difference in adult animals by size. The female is usually slightly larger than the male. The claws of the male, on the other hand, are larger than those of the females.

Diet

The diet of Procambarus clarkii consists mainly of plants. Soft and hard leaves from Java Fern to Java moss are cut into pieces and eaten. They are not picky about what they eat. Frozen foods that sink to the bottom, such as tubifex and mosquito larvae, are often eaten. If you’ve kept them in the tank for a while, they will come out curious about food as soon as you put your hands over the tank. With their scissors pointing upwards, they are waiting to see what you have in store.

If they get the chance, they also grab live fish with their claws. They cut the fish into pieces and eat the fish at their leisure. Usually, it is sick fish that fall prey to the claws of this lobster, but a careless fish can sometimes have bad luck.

Biotope

Originally, the Red Swamp Crawfish lived in North and Central America, from Illinois to Florida and Mexico. They inhabit the rivers, creeks and swamps. You can also encounter them outside the water. They are perfectly able to leave the water and do this regularly in search of food. Underwater they build tunnels in the mud where they can take shelter.

This lobster is now found in many more areas. They have been introduced in South America, Europe, North Africa and Asia, among others. In the United States, this lobster was used as a by-product in the cultivation of rice. In the rice fields, the lobster was released and caught for consumption. Meanwhile, Procambarus clarkii has become an invasive species in many countries.

Invasive Species – Lobster Plague

The main reason that Procambarus clarkii can become an invasive species is the crayfish plague (Aphanomyces astaci). This is a type of fungus that attaches to lobsters. Once the fungus has found a lobster, the fungus develops a kind of network (mycelium) in the flesh of the lobster. The fungus feeds on the lobster, eventually killing it. The Red Swamp Crawfish can carry the fungus alive but suppresses and encapsulates it effectively. As a result, he is a carrier of the fungus but does not suffer from it.

Without a live carrier, the fungus disappears after a few days. By removing the American lobsters you can also remove the live fungus. It is then possible to reintroduce the native species.

Prohibition of holding and trading Procambarus clarkii in Europe

In addition to the lobster plague, Procambarus clarkii has a number of other negative properties.

• they dig in banksides and damage revetments
• they strip the banksides of plants
• digging makes the water cloudy where it should be clear and much more nutrients get into the water

This has an effect on peat formation, for example, but also native fish species, amphibians, insects and even birds are affected by this. They are otherwise harmless to humans, although they do come out of the water and can be found in gardens, playgrounds or even the home.

Since August 2016, they have therefore been on the list of invasive exotics. They may no longer be held or traded in the EU. Unwitting private individuals still offer this species under other names. Especially the specially coloured variants can still be found.

Breeding Red American Crayfish

During mating, the female is placed on her back by the male. He holds the female with his scissors and the hooks on his legs. See the video below:

Commercial breeding of Procambarus clarkii

Procambarus clarkii is widely bred for consumption. They can be bred in large numbers in rice fields. The crawfish are caught by pumping a field dry. The crawfish will then crawl to new water by themselves and can be easily scooped up. They can also be caught by traps. With a little bit of baitfish and a steel cage, the crawfish are easy to catch. The traps in the shallow water are emptied every day with a small boat. The crawfish are eaten boiled, fried or baked.

See the video below about breeding of Procambarus clarkii in rice fields:

Video

Author

John de Lange

Copyright images

AquariumGlaser.de
Javier Colmenero – CC BY-ND 2.0
Rachid H. – CC BY-NC 2.0

Resources

Wikipedia
Procambarus Clarkii – Het Aquarium – Januari 1996 – Arend van den Nieuwenhuizen
Nederlandsesoorten.nl
Nederlandse Voedsel en Warenautoriteit