The economic impact of Australian redclaw crayfish Cherax quadricarinatus on the Barotse floodplain artisanal fishery

Biological invasions cost global economies billions of US dollars through direct control and mitigation, corrosion of ecosystem services and incurred management costs. Available evidence suggests that, the widespread introduction of redclaw crayfish Cherax quadricarinatus in the Zambezi basin has the potential to cause severe socio-economic impacts, however, this remains largely unquantified. In this study, roving creel surveys were implemented to assess the economic impact of C. quadricarinatus on the Barotse floodplain artisanal fishery. Fishers encountered C. quadricarinatus as a bycatch species in 9 types of fishing gears across the floodplain with crayfish encounter and abundance being higher in dry season and highest in the invasion core (Mongu). Damage to fish catch was mostly incurred by gillnet users and was also more extensive at invasion core during dry season. Damage was evident on 15 of the 16 fish species/group harvested. The economic cost arising from fish damage at the invasion core during dry season was estimated to be US$ 21, 586.76 per annum. Gear damage due to crayfish occurred in six types of fishing gear but was most prevalent among gillnet users, higher in the dry season and most extensive at the invasion core. The loss of fishing time was most prevalent among fishers using seine nets and more common in dry season and mostly at the invasion core. The economic costs incurred are significant for those affected, but the relative spatial restriction of such to the invasion core reflects a new invasion, the costs of which are likely to increase. These findings highlight the threat posed by invasive species to the livelihood of African communities, and the need to prioritise management of biological invasions in the region.