Expert Topic - Farmed Crayfish
Crayfish are low on the food chain, which makes them very easy to look after and stock in small aquaculture systems. They can be easily grown at low densities. There is a long history of freshwater crayfish farming worldwide, particularly in the United States and Europe with more recent industrial development in Australia.
American crayfish species
In America, the most commonly farmed species are the red swamp crayfish (Procambarus clarkii) and the white swamp crayfish (P. acutus). These are both indigenous species to these areas but they have been exported (alive) to many other continents, where they are now produced. The crayfish industry is the largest commercial crustacean aquaculture industry in the United States with an annual harvest exceeding 45 million kg. The predominant commercial species is the red swamp crayfish.
In the southern USA, red swamp crawfish and the white swamp crawfish are cultured in shallow ponds with a water depth of 300 to 600mm. Deeper ponds are sometimes used in very hot areas.
Although total production remains quite small Redclaw aquaculture has been established for more than 25 years. This despite many projections that it would become a significant aquaculture species worldwide, and possibly a rival of the giant freshwater prawn (Macrobrachium rosenbergii).
There is no hatchery production. Redclaws are reared directly in juvenile ponds where it obtains the bulk of its food from decaying matter and associated microbes contained in the pond bottom mud. Commercial crayfish pellets are available and have proven to be effective. A feeding frequency of once per day is adequate, preferably at dusk when crayfish are active.
UK crayfish farming
There are about 80 crayfish producers in the UK and supplies are available from July to October, the crayfish "season". Several types of production system exist, the most popular being extensive ranching or semi-intensive systems.
Ranching is favoured if crayfish farming is only an addition to a mainline enterprise. The ponds only need to be stocked and the crayfish breed and multiply naturally with the surplus crayfish harvested. Semi-intensive or intensive production systems exercise more control over the aquatic environment, feeding, etc. and the labour requirements are higher (much higher construction and management costs).
The enterprise is more suited to southern England than most of Scotland and has yet to be proved to be a viable commercial enterprise on a long-term basis.
Australian Crayfish Species
Australian marron (Cherax tenuimanus) is a species commonly grown both inside and outside of Australia. It is a spiny, non-burrowing freshwater crayfish found naturally in Western Australia. It is the highest valued freshwater crayfish farmed in Australia.
Another Australian crayfish that has also received some attention from growers worldwide is the yabbie (Cherax destructor). Care has been taken not to import the yabbie into other countries (like South Africa) because it is an aggressive burrower and could become an ecological problem (invasive species) under local conditions, though marron is farmed commercially in that country.
"Herax quadricarinatus, referred to popularly by its Australian synonym "redclaw", is a tropical species native to the rivers of north-west Queensland and the Northern Territory in Australia.
Although well known to the local inhabitants of this isolated region, it remained effectively unknown to the rest of the world until the late 1980s, when it was trialled for aquaculture. Redclaw proved to be well suited to cultivation, and the redclaw aquaculture industry was born, developing quickly and spreading throughout northern Australia, and soon afterwards overseas.
Redclaw benefits from a host of physical, biological and commercial attributes that make it an excellent candidate for aquaculture. It is physically robust with broad geographic potential, has a simple life cycle and straightforward production technology, requires low protein diet and is economic to produce.
Its texture and flavour compare very favourably with commonly eaten marine crustaceans and, having the appearance of a lobster, is positioned at the premium end of the crustacean market spectrum.
New Zealand species
In New Zealand freshwater crayfish have been farmed since the 1960s, although crayfish aquaculture is still in an early development stage with no farm currently producing large volumes of saleable stock.
Moreover, differences in environmental conditions suggest that Australian or American intensive farming systems may not be suited for New Zealand conditions; (e.g., warmer water temperatures and crayfish that mature in one year).
Asian Crayfish farming
Despite Asia being a leading farmer of shrimp and prawn (another crustacean), crayfish farming is only just emerging, with most crayfish being imported from the USA and other countries. The reason for the slow entry into crayfish farming is understandable.
Crayfish have long been the scourge of rice farmers, as crayfish burrows undermine rice paddies and render them unfarmable.
However, countries such as China are currently experiencing "Crayfish mania," as the small red lobsters have become a favourite cuisine.