Marron crayfish (Cherax tenuimanus, also known as Hairy Marron and Cherax cainii, known as Smooth marron), is a larger crayfish species endemic to Western Australia.
However, Marron crayfish have specific care requirements to thrive in captivity. Recreating key elements of their natural habitat is key to their health and longevity.
In this article, I will examine the biology, habitat, behavior, diet, and care needs of Marron crayfish.
|Note: There are 2 types of crayfish that share the same name “Marron crayfish”.
However, despite being so closely related and similar to each other both physiologically and genetically, to the extent of potential hybridization, Cherax cainii has proven to be more successful and better adapted to survival.
Nowadays, Cherax tenuimanus is currently listed as rare under the Western Australian Wildlife Conservation Act 1950 and is managed as ‘critically endangered’ (according to IUCN criteria) by the Western Australian Government (CALM 2005).
Quick Notes about Marron Crayfish
|Scientific Name||Cherax tenuimanus/Cherax cainii|
|Other names||Hairy Marron/Smooth marron|
|Tank size (minimum)||15 gallons (~60 liters)|
|Size||up to 15 inches (38 cm) long|
|Optimal Temperature||68 – 75°F (20 – 24°C)|
|Optimal PH||7.0 – 9.0|
|Optimal GH||8 – 20|
|Life span||up to 10 years|
Taxonomy of Marron Crayfish
In 1912, Cherax tenuimanus was first described and identified as a single species by G.W. Smith. Several subsequent studies of Cherax taxonomy also referred to only a single species.
In the 1980s, another closely related crayfish species was discovered in the same region. Based on differences in electrophoretic and morphological characteristics between animals, Marron crayfish were split into two subspecies.
Subspecies classification was maintained in subsequent marron classifications.
In 2002, a new subspecies was elevated from sub-species to species based on a review of allozyme data collected intermittently and was assigned the new name Cherax cainii.
Etymology of Cherax Tenuimanus/Cainii
The generic name Cherax is thought to be derived from the Greek word “Kherax,” which means “a kind of lobster” or “crayfish”. At the same time, it can be a misspelling of the Greek word ‘charax’, meaning a pointed stake, or a thing that scratches as a reference to the sharp, pointed rostrum (beak) and spiny claws that can scratch.
The species name “Tenuimanus” is a combination of two Latin words: “Tenuis,” which means “Thin or slender”, and “Manus,” which means “Hand” or “Limb.”
So, “Tenuimanus” refers specifically to the slender, thin claws or chelipeds of this crayfish species compared to others in the Cherax genus.
The etymology highlights a distinct morphological feature used to differentiate Cherax tenuimanus from close relatives.
Natural Habitat of Marron Crayfish
Cherax tenuimanus (Hairy marron or Margaret River marron) is endemic to the Margaret River in southwestern Australia. The Hairy Marron is naturally restricted. The species is currently known from only eleven sites along a section of the Margaret River and occurs in an area less than 50 km in length.
Cherax cainii (Smooth marron) occurs over much of the south-west of Western Australia (as far east as Esperance and as far north as Geraldton) where it forms the basis of a popular recreational fishery and aquaculture industry. Even more, recently, this species was introduced into South Africa, Zimbabwe, Japan, the USA, China, and the Caribbean as a commercial aquaculture species.
These crayfish prefer clear, fast-flowing streams and rivers with sandy bottoms and abundant vegetation. The water is soft, acidic, and high in tannins.
Description of Marron Crayfish
Size. These are one of the largest crayfish species in the world which can grow to more than 15 inches (38 cm) in total length having been recorded more than 4.4 lb (2 kg)!
Note: For example, the Smooth marron crayfish can grow to between 0.15 – 0.3 lb (60 – 150 g) in 12 months, and between 0.2 – 0.7 lb (100 – 300 g) in 24 months.
- Carapace differences. Hairy marron crayfish have a median carina that extends continuously, without depression, to the cervical groove. Additionally, there are prominent tufts of long recumbent setae; and the absence of tuberculation on the areola compared to Smooth marron.
- Telson. Marron crayfish are easily distinguished from all other Cherax species because they are considerably larger and possess spines on the telson.
- According to the study, these crayfish generally have a dark-marron coloration. This is a good camouflage in southern waters rich in brown tannins. However, there is also an electric blue variety now raised for aquariums and recently an orange striped marron was found in the south-west.
Lifespan of Marron Crayfish
Some reports indicate they may live over 10 years in optimal tank conditions. Their lifespans in nature are impacted by predation, disease, and environmental factors.
Typical Behavior of Marron Crayfish
Marron crayfish are crepuscular or nocturnal animals. They are most active just after sunset. During the day they tend to remain hidden under logs, rocks, and debris.
They are not social creatures and generally do not share the same hiding spots. For the most part, they are solitary.
This species can be aggressive toward each other and other crayfish species, especially when defending territory, competing for food, or during mating. The males in particular tend to fight using their large front claws. When threatened, they can move rapidly backward by curling and unfolding their abdomens.
Marron crayfish are a non-burrowing species. Instead of burrowing deep tunnels, they prefer to live under a shelter.
- Social: No
- Active: No
- Peaceful: No
- Territorial: Yes
- Burrowers: No
Diet of Marron Crayfish
These crayfish are omnivorous scavengers, feeding on both plant and animal matter. They are not picky eaters and will consume a wide variety of food such as:
- aquatic plants,
- decaying vegetation,
- dead or decaying organic matter,
- small insects,
- insect larvae,
- fish eggs/fry, etc.
Just like other crayfish species, Marron crayfish are opportunistic feeders and adjust their diet based on food availability in their local habitat.
Based on numerous studies, it can be concluded that for optimal growth these crayfish require a diet consisting of 30-40 percent protein and in the ratio of 10-15% of their body weight per week. Thus, in the case of daily feeding of these animals, it will be about 2% of their body weight per day.
However, since this can be difficult to calculate, it will be sufficient if the size of the food does not exceed the size of the carapace.
If these crayfish are kept as pets in aquariums, suggested foods include:
- blanched vegetables,
- crushed snails,
- dead fish or shrimp,
- detritus worms,
- tubifex worms,
- blackworms, etc.
- Diet Type: Omnivorous
- Food Preference: Mix of meats and vegetation.
- Feeding Frequency: 3 – 4 times a week for adults. Daily for juveniles.
- Schedule. Feed them before lights out.
- Leave their food for 24 hours before removing it. To prevent water contamination, leftover feed should be removed by siphoning before fresh food is added. Leaves can be left for several days in the tank.
- Leave old exoskeletons. Do not remove molted exoskeletons to improve health.
- Check their hiding places. Keep in mind that Marron crayfish often drags and stores food in their hiding spots for later consumption. Check them from time to time to prevent any bacterial contaminations.
- Crayfish need diversity in food. Do not give them the same food all the time. Change their diet periodically.
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Are Marron Crayfish Plant Safe?
No, these crayfish are not compatible with live plants. Like most crayfish species, they will try to eat, cut, shred, and uproot everything in the tank.
Therefore, it is not recommended to keep them in planted tanks. The only viable options for this species are:
- Plastic plants,
- floating plants,
- some cheap plants that you are ready to lose.
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Marron Crayfish: Calcium and Molting Cycle
All crustaceans have a hard multi-layered exoskeleton (shell). However, exoskeletons do not grow as the animal inside them grows. Therefore, Marron crayfish are forced to molt as they grow bigger.
Calcium (Ca) is an essential component of the exoskeleton composition. So, growing a new exoskeleton requires a high amount of Ca to facilitate calcification. The process of molting puts them in a vulnerable state.
When Marron crayfish are about to molt they become less active, stop eating, and seek shelter. Otherwise, they can easily fall prey to their tankmates.
Tank Requirements and Water Conditions
In natural habitats, areas with cool, flowing, well-oxygenated water allow marron crayfish to thrive, while they tend to avoid stagnant backwaters. Overall, ideal marron habitat consists of freshwater environments with plentiful vegetation, woody debris, rocky banks, and muddy substrates that enable these crayfish to easily meet their cover and dietary needs.
The minimum recommended tank size for one Marron crayfish is a 15-gallon (60-liter) tank. A pair (male and female) will require at least 40 gallons (120 liters). Remember these crayfish grow huge!
Of course, having a larger tank is always preferable for the stability of water chemistry. In addition, it can be easier to make diverse areas for them to hide.
- Keep in mind that having too many crayfish in insufficient space will definitely lead to increased aggression, injuries, and cannibalism. Overcrowding is the main source of stress for crayfish. This is particularly important when you have more than one male, as they are more aggressive than females.
- Long tanks are better than tall tanks of the same size for keeping any crayfish species. Unlike fish, they need mostly a place to crawl from side to side, not up and down.
- Crayfish are very good escape artists. It is absolutely necessary to cover the tank. Keep in mind that they are strong enough to move the lid. Make sure your tank has a stable lid!
Temperature: The ideal water temperature for Marron crayfish is between the range of 68 – 75°F (20 – 24°C). Although they can tolerate low temperatures, they stop growing at water temperatures under 55°F (12.5°C). It was also observed that their growth declines rapidly above 75°F (24°C) as well, with mortality occurring at 86°F (30°C) and above.
pH: Optimal water pH should be provided for this species in the range of 7.0 – 9.0.
Hardness: These crayfish will appreciate hard water GH between 8 – 20.
Oxygen: Dissolved oxygen levels should be maintained at or above 6 mg/L. They become stressed when levels drop below 3 mg/L. They need good aeration and water flow.
Salinity: Experiments showed that Marron crayfish may tolerate, although not necessarily be able to reproduce in, salinities ranging from 0 to 15 ppt. Their growth decreases at salinities above 6-8 ppt.
There are no special requirements. As long as you have got the filter that works great with the size of the tank you have got you will be fine.
Note: However, having sponge filters with Marron crayfish can be a bad idea. The point is that they like to chip and chew on it. With time, they will simply shred and break apart the sponge.
No special requirements. They are nocturnal animals and used to live with very little light.
If you have plants or other animals in the tank, lighting should be adapted to their needs.
No special requirements. These crayfish are not diggers.
Decorations in an aquarium play a role that goes beyond pleasing us visually.
For the crayfish, they serve different functions, specifically providing shelter. So, the more decorations you have, the happier your pets will be.
They will appreciate all types of leaves, rocks, driftwood, PVC pipes, etc. in your tank.
Breeding Marron Crayfish
According to studies, Cherax cainii grow slightly faster than Cherax tenuimanus, and they are also more readily bred, including in captivity. Moreover, these two species can successfully hybridize.
According to the study, Marron crayfish take at least 2 to 3 years to reach sexual maturity at a total body length of 3.1 – 4.3 inches (8-11 cm) in length.
The eggs take nearly half a year to develop inside the females. The male deposits a spermatophore between a female’s 5th pair of legs.
On average, females incubate 200-400 eggs for 12-16 weeks on pleopods under the tail (but large females may produce up to 800), from which about 150-250 juveniles will be released.
Newly hatched young crayfish are incapable of living separately from the mother for a further 2-4 weeks. They need to molt before they become completely independent.
Females whose young have become independent should be separated from females still carrying eggs or young to prevent cannibalism.
Marron Crayfish and Suitable Tankmates
It is not recommended to keep Marron crayfish with other crayfish species or even conspecifics for 2 main reasons:
- They grow really big.
- They will fight eventually and more aggressive crayfish species can become dominant.
Bottom-dwelling, slow-moving, or fish with long fins (like Betta) will be the first ones to get hurt.
Marron crayfish are very large freshwater crayfish.
There are two main species – the rarer hairy marron (Cherax tenuimanus) and the more common smooth marron (Cherax cainii). Nonetheless, both are omnivorous nocturnal scavengers that reach up to 15 inches in length and can easily hybridize.
If you decide to keep these crayfish as pets, you should be aware of their impressive size, aggressive nature, and the limited choices of potential aquarium mates for them.
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