Common Yabby, Yabbie; Cherax davisi (Clark, 1941), Cherax esculus (Riek, 1956)

The length of C. destructor often ranges between 10 to 20 cm but occasionally will grow to 30 cm (Gherardi and Allen 2022). In Australia, the average common yabby caught by amateur anglers usually weighed between 20 g to 80 g. Females will experience a reduced growth rate after maturity is reached, likely in response to the energy requirements of spawning; for this reason, females are often smaller than males, who can grow up to 300 g (NSW Department of Primary Industries 2017).

Cherax destructor is an omnivorous species that feeds on plants, detritus, and some arthropods (Gherardi and Allen 2022). Their diet also switches according to climate. During summer seasons, they tend to eat fish, and in the winter, they eat plants and detritus (Beatty 2005). Cherax destructor may have cannibalistic tendencies in areas where there is an overabundance of the species and low levels of natural food sources (Gherardi and Allen 2022). Yabby have shown antagonistic behavior to get access to limited resources. In a trial competition between yabby and the marron, Cherax tenuimanus, yabby won. They concluded that its aggression led to success (Gherardi 2007).

The yabby has a high fecundity and reproductive characteristics that would support establishment (Geddes and Smallridge 1993, Gherardi 2007). Females are capable of reproducing five times a year in suitable conditions and reach sexual maturity at less than one year old. Clutch size is typically 300 to 500 eggs but instances of large females carrying 1400 eggs have been reported (Kouba et al. 2021). Females carrying eggs provide parental care by ensuring a well oxygenated environment and keeping eggs clean and free of foreign particles (Withnall 2000).

Potential pathway(s) of introduction: Unauthorized intentional release

Yabby is not currently in waters connecting to the Great Lakes and is not known to be transported through the Great Lakes region. However, it has been increasingly transported globally which could increase the future risk of introduction into the Great Lakes. Cherax destructor was originally transported for aquaculture and food, but more recently, it has gained popularity as a pet (Chucholl 2013). When used as bait, unused live bait is often directly discarded into the water (Gherardi 2007).

Cherax destructor is NOT currently found in the Great Lakes region; nor are there wild populations established elsewhere in the U.S. The species is available in the United States in areas outside the Great Lakes region through the pet trade. Shipping for aquarium trade between the United States and Europe decreased due to crayfish plague, which originated from the crayfish brought from the US; the plague was first recorded in 1859 and removed up to 95% of the indigenous European crayfish species (Chucholl 2013). Cherax destructor is currently a regulated species in a majority of the Great Lakes states and is listed as an injurious species at the federal level. Despite the regulations, the yabby is available for purchase online through several vendors and is considered a common species to be found in aquariums (Chucholl 2013). However, the availability of C. destructor in the pet market may have declined as recent research reported its availability as rare with an expensive price point compared to other non-indigenous crayfish species (Vodovskoy et al. 2017). This species is still available for purchase and the pet trade remains a potential pathway for introduction.

Cherax destructor has a Moderate probability of establishment if introduced to the Great Lakes (Confidence level: High).

The Great Lakes provide an abundant habitat that is suitable for the survival, development, and reproduction of this species. Yabby’s ideal habitat consists of high oxygen levels and vegetation; they are most likely to be found in swamps, streams, rivers, and dams (Withnall 2000). Climate suitability analysis suggest C. destructor has a high climate match with the United States and was identified as a species with the potential to overwinter in the Caspian Sea region, suggesting a similar potential in the Great Lakes (USFWS 2019, Vodovskoy et al. 2017).

Cherax destructor is known to have a high tolerance to a variety of environments. They have been found in regions with climates similar to the Great Lakes. Yabby prefer muddy waters opposed to clear water environments (Withnall 2000), and they survive dry periods by burrowing in the mud (Geddes and Smallridge 1993). The extreme temperatures near the Great Lakes may affect the growth of Yabby during some seasons, but their high proliferation would help them survive. Cherax destructor is an opportunistic feeder with a flexible diet and would likely be able to find a food source in the Great Lakes. The mosquitofish Gambusia affinis constitutes a majority of the summer diet outside of their native range in Australia and their diet shifts to plants or detritus when resources are scarce in winter. G. affinis is present in two of the Great Lakes (Lake Erie and Lake Michigan) and similar prey items are present throughout the region (Cudmore-Vokey and Crossman 2000).

Predators of yabby include aquatic birds, such as cormorants, herons, and ibis, and all three of these are found in the Great Lakes region (Farrell and Leonard 2001, MSG 2007). There have been no reports of predation limiting the spread or establishment of C. destructor outside of its native range.

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

If introduced to the Great Lakes, C. destructor has the potential to alter the aquatic food web and negatively impact native crayfish through competition and the spread of disease. Due to its aggressive behavior and size, this species is capable of out-competing native species for resources. Ample research has emerged that supports the yabby’s impact on native crayfish through behavioral interactions or competition for resources (Lopez et al. 2018, Cerato et al. 2019, King et al. 2022, O’Hea et al. 2022). The yabby is considered a keystone species that influences the aquatic food web through nutrient recycling (Beatty 2005). This species is a carrier for the parasite Aphanomyces astaci, which is responsible for the crayfish plague, and a host for two parasites that can cause thelohaniasis, commonly referred to as porcelain disease, Thelohania montirivulorum, and Thelohania parastaci (Gherardi 2007, Chucholl 2013, Pretto et al. 2018).

There is little or no evidence to support that Cherax destructor has the potential for significant socio-economic impacts if introduced to the Great Lakes.

C. destructor exhibits a burrowing behavior that can alter the habitat by destabilizing the banks of lakes, rivers, and streams, the effects of this behavior have not been widespread or severe (Holdich 1999).

Cherax destructor has the potential for moderate beneficial impact if introduced to the Great Lakes.

Cherax destructor has commercial value but its economic contribution is small. It has become a target species for aquaculture in several countries and is employed recreationally as bait but adds little value to local communities or tourism. This species has demonstrated utility in laboratory use and in research as a model organism (Gherardi and Allen 2022).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological

If C. destructor were to become established in the Great Lakes basin, populations might be controlled by predatory fish. Eels, burbot, perch, pike, and smallmouth bass are some well-known predators of crayfish that exist in the Great Lakes (Westman 1991 in Gherardi et al. 2011). One study observed in a mesocosm experiment that northern pike (Esox lucius) were an efficient predator of crayfish independent of prey size (Neveu 2001 in Gherardi et al. 2011), which could be significant considering the large size of C. destructor. Fish predation could be effective in managing C. destructor, but some studies have suggested that stocking predacious fish could actually increase non-indigenous crayfish species population densities (Gowing and Momot 1979, and Holdich and Domaniewski 1995 in Gherardi et al. 2011). Predatory aquatic birds, such as cormorants, herons, and ibis are predators of C. destructor and all exist in the Great Lakes region (Farrell and Leonard 2001).

The use of microbial agents to control crayfish populations has been reviewed in previous studies (Gherardi et al. 2011; Scalici et al. 2009). C. destructor is known to be susceptible to the crayfish plague, Aphanomyces astaci (Scalici et al. 2009), of which North American species are much more resistant (Persson et al. 1987; Unestam 1975). Four populations of C. destructor in Spain were eradicated by introducing signal crayfish (Pacifastacus leniusculus) infected with the plague into the populations (Diéguez-Uribeondo and Muzquiz 2005 in Peay 2009). The crayfish plague was responsible for the eradication of C. destructor in the Laghi di Ninfa Natural Reserve, Italy. The disease was brought to the area by another invasive crayfish, Procambarus clarkii (Mazza et al. 2018). P. clarkii is already present and spreading in the Great Lakes region. C. destructor is also susceptible to the microsporidian disease, Thelohania parastaci (Moodie et al. 2003) and the Cherax destructor systemic parvo-like virus (CdSPV) (Edgerton 1996, Edgerton et al. 1997 in Diggles 2011). Gherardi et al. (2011) mentions that the use of genetically modified strains of A. astaci has been hypothesized as a potential way to control invasive crayfish in Europe, but there is a significant risk that using a genetically modified strain in conjunction with the existing wild-type could affect more than just the target species. The use of microbial agents as a method of control for C. destructor in the Great Lakes basin would also warrant the consideration of indirect effects on native crayfish populations.

Aside from predatory fish and disease, other potential methods of control would be the use of sex pheromones or the release of sterile males. Aquiloni and Gherardi (2010) observed the capability of sex pheromones as a method of control in another species of crayfish, which could have implications for the control of C. destructor if it becomes established in the Great Lakes. Additionally, the release of sterile male C. destructor into a population could be an effective method of control if the species were to become established within the Great Lakes basin. The sterile male release technique is species-specific and has been tested for other species of invasive crayfish in laboratory settings (Aquiloni et al. 2009).

Chemical

The use of chemical agents to control C. destructor populations has been examined by Gherardi et al. (2011) and the New South Wales Department of Primary Industries (2017). In particular, the assessments of insecticides as a possible control of crayfish populations could provide insight on the viability of this control method for C. destructor. C. destructor is susceptible to organochlorines found in some insecticides and herbicides (NSW Department of Primary Industries 2017). Gherardi et al. (2011) noted the success of insecticides derived from natural pyrethrum and synthetic pyrethroids in eradicating crayfish populations in Europe (Gherardi et al. 2011). Organophosphate insecticides (e.g. fenthion and methyl parathion) have also been utilized in attempts to eradicate invasive crayfish species, but these organophosphates apparently lack specificity among crustaceans and insects (Gherardi et al. 2011), so using this control method may harm native species as well as C. destructor. Two insecticides (active ingredients cypermethrin or deltamethrin) were found to be suitable biocides for eradicating crayfish populations. These insecticides are highly toxic to crayfish at low concentrations, have low accumulation rates in the food chain, and do not persist in aquatic environments long-term (Lidova et al. 2019). Other studies have observed the effect surfactants have on controlling crayfish activity, but this method has shown to have a limited effect in the eradication of populations (Cabral et al. 1997 and Fonseca et al. 1997 via Gherardi et al. 2011). Salt can be used as a chemical control in confined settings; C. destructor will die at a salinity of 25 ppt or above (NSW Department of Primary Industries 2017).

Physical

The use of physical barriers and diversions have been reviewed as a method to control non-indigenous crayfish species populations in Europe and America (Gherardi et al. 2011; Kerby et al. 2005). Kerby et al. (2005) observed that red swamp crayfish (Procambarus clarkii) movement was significantly reduced by natural barriers. Other physical control methods include the use of electric fences and vibrations (Gherardi et al. 2011). Mechanical removal of C. destructor could also be a potential control method. Continuous trapping has been demonstrated to work on rusty crayfish (Faxonius rusticus) in a Northern Wisconsin lake (Hein et al. 2007) as well as in aquaculture ponds (Bills and Marking 1988). Gherardi et al. (2011) suggests that electrofishing and trapping could also be an effective way of controlling non-indigenous crayfish species populations.

Note: Check state and local regulations for the most up-to-date information regarding permits for pesticide/herbicide/piscicide/insecticide use.