Distribution and establishment of the alien Australian redclaw crayfish,Cherax quadricarinatus, in South Africa and Swaziland

Abstract

BackgroundThe Australian redclaw crayfish (Cherax quadricarinatus, von Martens), is native to Australasia, but has been widely translocated around the world due to aquaculture and aquarium trade. Mostly as a result of escape from aquaculture facilities, this species has established extralimital populations in Australia and alien populations in Europe, Asia, Central America and Africa. In South Africa, C. quadricarinatus was first sampled from the wild in 2002 in the Komati River, following its escape from an aquaculture facility in Swaziland, but data on the current status of its populations are not available.MethodsTo establish a better understanding of its distribution, rate of spread and population status, we surveyed a total of 46 sites in various river systems in South Africa and Swaziland. Surveys were performed between September 2015 and August 2016 and involved visual observations and the use of collapsible crayfish traps.ResultsCherax quadricarinatus is now present in the Komati, Lomati, Mbuluzi, Mlawula and Usutu rivers, and it was also detected in several off-channel irrigation impoundments. Where present, it was generally abundant, with populations having multiple size cohorts and containing ovigerous females. In the Komati River, it has spread more than 112 km downstream of the initial introduction point and 33 km upstream of a tributary, resulting in a mean spread rate of 8 km year−1 downstream and 4.7 km year−1 upstream. In Swaziland, estimated downstream spread rate might reach 14.6 km year−1. Individuals were generally larger and heavier closer to the introduction site, which might be linked to juvenile dispersal.DiscussionThese findings demonstrate that C. quadricarinatus is established in South Africa and Swaziland and that the species has spread, not only within the river where it was first introduced, but also between rivers. Considering the strong impacts that alien crayfish usually have on invaded ecosystems, assessments of its potential impacts on native freshwater biota and an evaluation of possible control measures are, therefore, urgent requirements.

Contributions to the knowledge of Pseudolevinseniella (Trematoda: Digenea) and temnocephalans from alien crayfish in natural freshwaters of Thailand

“…The redclaw crayfish ( C. quadricarinatus von Martens, 1868) inhabits Australian freshwater and has been introduced to other countries, such as for aquaculture farming (New, 2003; Patoka et al., 2016), because it is tolerant to various environmental conditions (Lin et al., 1999; Jones et al., 2000). Redclaw crayfish are considered an invasive species in several counties, including Uruguay, Mexico, Puerto Rico, South Africa, Zimbabwe, Swaziland, Malaysia, Singapore and Indonesia (Williams et al., 2001; Ahyong and Yeo, 2007; Volonterio, 2009; du Preez and Smit, 2013; Vega-Villasante et al., 2015; Naqiuddin et al., 2016; Nunes et al., 2017; Marufu et al., 2018; Jiří et al., 2016). Moreover, Wanjit and Chaichana (2013) and Chaichana and Wanjit (2018) collected redclaw crayfish from a reservoir in Sa Kaeo Province, Thailand.…”

South Africa as a Donor of Alien Animals

“…Hey was also responsible for supplying tertiary and research institutes with African Clawed Frogs (van Sittert and Measey 2016). The actions of individuals continue to impact invasions in the region, as seen by the relatively recent activities of Adrien Piers introducing Red Claw Crayfish into Swaziland (and their subsequent invasion into South Africa and Mozambique: Nunes et al 2017b;Weyl et al 2020, Chap. 6), Zambia and from there to Zimbabwe (see Welz 2017).…”

“…For example, C. quadricarinatus was also introduced into the Kafue River in 2001 from Swaziland, and it has since appeared in the upper and middle Zambezi sub-catchments after escaping from nearby fish farms (Douthwaite et al 2018). Elsewhere, C. quadricarinatus escaped from aquaculture facilities in Swaziland and as a result of downstream spread and subsequent dispersal, it is now established in several river systems in Swaziland, South Africa and Mozambique (Nunes et al 2017b). The C. quadricarinatus invasions in southern Africa, including ongoing invasion in South Africa, are some of the worst on the continent.…”

Assessing the potential impacts of non-native small mammals in the South African pet trade

“…In cases where non-native pet species have already been introduced but not yet established, possible impacts can be avoided by preventing their release or escape from captivity (da Rosa et al 2018). In South Africa, the pet trade has been cited as an invasion pathway for different non-native animals through releases and accidental escapees, including species such as the mallard duck Anas platyrhynchos (Gaertner et al 2015), the rose-ringed parakeet Psittacula krameri (Hart and Downs 2014), and the Australian red claw crayfish Cherax quadricarinatus (Nunes et al 2017). The South African National Environmental Management: Biodiversity Act (No.…”