Aquaponics - Marron

Apparently, marron come in two varieties. Hairy and not so hairy. Cherax cainii (smooth) and Cherax tenuimanus, or Margret River marron (hairy).

fine marron illustration*

Marron are a fresh water crayfish, native to Western Australia. They are a good candidate for farming because they have a good food conversion rate, so they grow well and don't cost too much to feed. They can grow up to a weight of 2 kg but are usually harvested for sale at between 100 to 200 grams at a little under 2 years of age. Marron rank equal to the highest percentage of meat to total body weight for similar under-water walking things.

They are active mainly at night, and are opportunistic feeders that will eat whatever they find. In the wild the majority of the food comes from plant material, small living and dead beasties, and detritus (decomposing plant matter colonized by fungi and bacteria.

They thrive in water temperatures ranging from around 13 deg C to 25 deg C. Water temperatures over 30 deg C will result in deaths.

Marron need a quarter of a square metre of space each when grown in a conventional dam or similar, but it may prove possible to increase the possible population density by using a multi level hi-rise approach, or with the addition of a stack of short lengths of PVC tubing to increase the available surface area, and allow lots of places to live and hide.

In order to grow, marron find a safe place to hide, then spend some time shedding their hard shell. Once shed, they expand into their new softer shell and go back to their normal lives until outgrowing themselves again. They may appear sluggish and generally disinterested in the world when about to shed their shells. If this happens, leave them alone and don't try to cheer them up by feeding them. When changing shells they go off their food for a while, and continued feeding runs the risk of fouling the water. As with all aquaponics feeding, feed only what is eaten right away, and stop feeding if food is left uneaten.

Marron can be grown in tanks or ponds as shallow as 20 cm, but beware their climbing and escaping abilities. Like other similarly shaped critters, they can walk on land and will wonder off in search of a good time if allowed to do so.

Marron don't like the sores they get on their undersides from bare concrete tanks so add something soft like sand, or fill the bottom of their tank with PVC tubing.

Apparently marron like to eat worms.

They also enjoy the type of pH levels found within aquaponics systems, and have a particular fondness for pH levels of between 7.0 and 8.5. They are found growing in the wild in water ranging from pH 6.0 to as high as pH 9.0.

Fresh water is best but they can tolerate saline levels of up to 15 parts per thousand. They thrive in salinity levels of less than 5 parts per thousand, and wont breed in higher salinity water.

*actual marron may have legs.