Distribution and establishment of the alien Australian redclaw crayfish, Cherax quadricarinatus, in the Zambezi Basin

Distribution and establishment of the alien Australian redclaw crayfish, Cherax quadricarinatus, in the Zambezi Basin

Crayfish are invasive polytrophic keystone species, which are phylogenetically unique on the African continent. The Australian redclaw crayfish Cherax quadricarinatus is invasive in southern African freshwater systems including the Zambezi River Basin. Surveys conducted across the Zambezi Basin (Bot...

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Bibliographic Details
Published in:Aquatic conservation Vol. 31; no. 11; pp. 3156 - 3168
Main Authors: Madzivanzira, Takudzwa C., South, Josie, Ellender, Bruce R., Chalmers, Russell, Chisule, Gethings, Coppinger, Christine R., Khaebeb, Fernandu H., Jacobs, Francois J., Chomba, Machaya, Musando, Bumango, Mwale, Chanda, Nhiwatiwa, Tamuka, Rennie, Craig L., Richardson, Naomi, Weyl, Olaf L. F.
Format: Journal Article
Language:English
Published: Oxford Wiley Subscription Services, Inc 01-11-2021
Subjects:
Barotse floodplain
Biosecurity
Carapace
Catch per unit effort
Cherax quadricarinatus
CPUE
Crayfish
Fisheries
Floodplains
Freshwater
Freshwater crustaceans
Freshwater ecosystems
freshwater invasions
Headwaters
Inland water environment
Interspecific relationships
Invasions
Invasive species
Kafue
Keystone species
Lake Kariba
Lakes
Okavango delta
Phylogeny
Population characteristics
population dynamics
Predation
Probability theory
Regions
River basins
Rivers
Sex ratio
Surveys
Transboundary pollution
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Summary:Crayfish are invasive polytrophic keystone species, which are phylogenetically unique on the African continent. The Australian redclaw crayfish Cherax quadricarinatus is invasive in southern African freshwater systems including the Zambezi River Basin. Surveys conducted across the Zambezi Basin (Botswana, Zimbabwe, Namibia and Zambia) between 2017 and 2019 showed that C. quadricarinatus is broadly distributed across the Upper and Middle Zambezi and is rapidly spreading through natural and human‐mediated means across several ecoregions. The probability of capture (Pcapture), catch per unit effort (CPUE) and population characteristics of C. quadricarinatus from the recent Barotse floodplain invasion were compared with older invasions from Lake Kariba and Kafue River. The Pcapture and CPUE of C. quadricarinatus in the recently invaded region of the Barotse floodplain were similar to those of the older invasions. Mass and carapace length of C. quadricarinatus from the Barotse floodplain were significantly lower than those of C. quadricarinatus from the older invasions. Sex ratios differed significantly between the three invasive populations. The Barotse floodplain population had a disproportionate investment in females (65.3%) and intersex individuals (8.4%). No crayfish were detected in the Zambezian Headwaters or the Okavango Floodplains ecoregions, but current spread rates are 49 km yr−1 downstream and 12 km yr−1 upstream. Investment in population management and the prevention of spread will have high conservation value across the invaded regions in order to restrict crayfish ecological impacts via direct predation and competition. In areas where crayfish are in high abundance, existing fisheries are affected through damage to nets, leading to increased net abandonment and ghost gear pollution in invaded regions. The emphasis should be on developing cohesive transboundary biosecurity policies in southern Africa to limit further spread that will threaten the integrity of freshwater ecosystems. However, long‐term monitoring is needed to gauge invasion risk to sensitive areas such as the Okavango Floodplains ecoregion and determine field‐based ecological impacts.
Bibliography:Funding information
National Research Foundation (NRF)‐South African Research Chairs Initiative of the Department of Science and Innovation (DSI) Inland Fisheries and Freshwater Ecology, Grant/Award Number: 110507; Worldwide Fund for Nature (WWF) Upper Zambezi Programme that is funded by DOB Ecology; WWF Shared Resources‐Joint Solutions (SRJS) strategic partnership between IUCN Netherlands, WWF Netherlands and the Netherlands Ministry of Foreign Affairs (DGIS); NRF–SAIAB Institutional Support system; DSI–NRF Centre of Excellence for Invasion Biology; DOB Ecology
Deceased
ISSN:1052-7613
1099-0755
DOI:10.1002/aqc.3703