Freshwater Crayfish in WA • Smooth Marron (cherax cainii) • Hairly Marron (cherax tenuimanus) • Yabbie (Cherax destructor) Not native to WA

Courtesy: DoF, WA

The Life cycle of a Marron Marron grow by moulting, the process of discarding and shedding an old body shell to grow a new body shell that starts off soft in texture. The new body shell of a Marron becomes hard by absorbing calcium and minerals that are stored in gastroliths (small, hard round pellets) in the marron’s body. Moulting frequency is higher in juvenile Marron and decreases as Marron get older. The body of the Marron can be divided into two parts, the cephalothorax (head and neck fused together) and the abdomen and tail. The head is covered by the carapace to protect the internal organs. Antenna and antennule are major touch and sense organs that are used to locate food. Juvenile marron are rarely seen. They hide under rocks and in forest litter that has settled in the river. The speckled colouring that provides them with camouflage changes as they grow older. Marron grow mostly in the summer months, when water temperature is warmest. They thrive in water that is 15 to 25 degrees Celsius. They grow by moulting. They shed their shell, exposing a larger shell, that had been forming underneath. During the short time that the new shell takes to harden, marron are especially vulnerable to attack. During the winter, with water temperatures below 12 degrees, marron are less active and their growth rate slows. Marron usually reach sexual maturity at two-to- three years old. They spawn in early spring when water temperatures start to rise and in favourable seasons will produce more eggs (usually between 200 and 400, but sometimes large females may produce up to 800). The eggs take nearly half a year to develop inside the females. During mating, the males pass on a sperm packet that the females use to fertilise their eggs after laying. Once the eggs are fertilised, the females then carry them in a large mass under their tails until they hatch in late spring. Females bearing eggs in this way are described as ‘berried’. The hatched marron larvae then hang under the mother’s tail, clinging to fine hairs. The larvae remain this way for many weeks, feeding on nutrients from the yolk sac and moulting several times. By summer, these tiny juveniles are ready to actively feed. They drop away from their mother and remain in waterways close to where they were hatched. Small juvenile marron are highly vulnerable to predation from other fish and animals, and cannibalism by larger marron.

Smooth Marron (YouTube).

The Marron Growers Manual If you’d like to find out much more about the biology and life cycle of Marron, you will find a wealth of facts, figures and advice in the Manual For Growers available from the Marron Growers Association. The Marron Aquaculture in Western Australia - A Growers Manual is an extensive practical guide for anyone who is starting up or investing in a marron farm in Western Australia, and for existing marron growers who wish to expand their productivity. Much of the book will also be of interest to anyone who wishes to know more about marron in general , or is passionate about marron as a gourmet food. It provides specific, useful and practical information for successfully growing marron in WA. The book finishes with a selection of marron recipes. Purchase your copy today!

River Recyclers Marron prefer to live in parts of rivers and dams where there is permanent water and plenty of suitable habitat and food. This includes rivers and dams with large woody debris such as fallen trees and submerged leaves. Within the river ecosystem, marron play a critical role as recyclers, breaking down animal and plant matter that sinks to the bottom. Marron are regarded as ‘benthic omnivores’. This means that they eat all kinds of living, dead and decaying plant and animal material found on the river or dam bed, including small invertebrates, fish eggs, fish larvae and algae. Large marron also attack and eat juvenile marron.

Decapod Has 10 legs Detritus Dead organic material Distribution Geographic area within which a species is generally found Endemic Native to or only naturally found in one place Moult Shed and discard an old shell in order to grow a new one Omnivore An animal that feeds on both plant and animal matter Range Geographic area, including all locations in which a species is recorded, even if only rare or single sightings Thorax Part of the body between the head and the abdomen

Marron Glossary Antenna (plural: antennae) A sensory organ found in pairs on the heads of insects and crustaceans Benthic Found in or near the river bed or dam bottom (or seabed) Berried When a female marron carries eggs attached under her tail Carapace Protective shell covering the marron’s head and thorax Crepuscular Active at twilight, or just after sunset Critically endangered A species that is at an extremely high risk of becoming extinct, or dying out Crustacean Animals with hard, jointed external skeletons, such as crabs, shrimp, lobster, prawns and marron

Marron References: Department of Fisheries, Western Australia www.fish.wa.gov.au Freshwater Fish Distribution in WA freshwater.fish.wa.gov.au Centre for Fish and Fisheries Research, Murdoch University www.cffr.murdoch.edu.au/curres/Freshwater.html Fisheries Research & Development Corporation www.frdc.com.au

Extract from the Marron Growers Manual - Internal organs of the male Marron ( Courtesy of DoF, Western Australia )

Marron prefer clean freshwater and permenant streams. Marron are poor burrowers and do not survive if their habitat dries out. They are also very intolerant to changing water quality but can adapt to various conditions if acclimatised slowly, In Nature Marron usually rest during the daytime and begin to forage for food at sunset. Natural population densities are closely related to the amount of shelter or food in the form of debris available. Such waters are classified as Oligotrophic Marron are opportunistic omnivores and in nature depends on plants enriched with microbes and detrius. Past research has shown Marron do selectively choose their food material. Marron growth rates are also variable and depend on factors such as population density, shelter, water temperature and availability of food. Dissolved oxygen is a critical consideration in Marron survival.