Growth and abundance of the introduced crayfish, cherax quadricarinatus (Von Martens, 1868) in the Kafue flood-plain and Lake Kariba, Zambia.

Cherax quadricarinatus is an Alien Invasive Species (AIS) native to Australia and Papua New Guinea, which has been introduced into Lake Kariba and the Kafue Floodplain and has since established its populations. Continued population growth and spread of C. quadricarinatus threatens the integrity of the two freshwater ecosystems. However, not much work has been done on its population dynamics. Comparative information on growth and relative abundance from this current study is cardinal to the long-term biodiversity management solutions of the two ecosystems. von Bertalanffy growth parameters asymptotic length (L∞) growth coefficient (k) was obtained in Elefan I of FiSAT II software and were used to compute growth performance index (Φ′). Relative abundance was estimated using catch per unit effort (CPUE) and conduciveness of Lake Kariba and the Kafue floodplain for the growth of C. quadricarinatus was assessed by length-weight relationships (W=aLb ) and the condition factor, K (K= 100W/L3 ). Analysis was done monthly and by sex. The class size-frequency analysis and CPUE revealed that the two study areas were lightly exploited. Kafue Road Bridge, a site near the central business district (CBD), experienced higher fishing pressure than Chanyanya a site located further from the CBD. Significant differences (P > 0.05) in carapace mean lengths on the Kafue Floodplain were due to differences in fishing pressure between sites. No dissimilarities were observed in growth performance between sites and there were no significant differences in the conduciveness of the two sites at Lake Kariba and the two sites at Kafue Floodplain fishery for the growth of C. quadricarinatus (P > 0.05). Cherax quadricarinatus is well adapted to Lake Kariba and Kafue Floodplain ecosystems. Future research could focus on formulating management strategies that would reduce negative impacts in areas where it has been introduced.

KEY WORDS: Relative abundance, Cherax quadricarinatus, condition factor, growth, Kafue Flood plain, Lake Kariba