A preliminary assessment of the length-weight relationship and condition factor of Hydrocynus vittatus and Oreochromis niloticus in Lake Kariba, Zimbabwe

Abstract

Background: Hydrocynus vittatus and Oreochromis niloticus are two economically important fish species in Zimbabwe. The length-weight relation can be employed to assess the health and well-being of fish so as to assist fish farmers. The objective of the study was to investigate the length-weight relationship and condition factor of these fish species. Methods: Thirty-four fish of each species (Hydrocynus vittatus and Oreochromis niloticus) were collected by seine netting in the Sanyati Basin, Lake Kariba in August 2019. The total length (TL) and standard length (SL) were measured in centimetre (cm), and the body weight (BW) was measured in grams (g). The body weight (BW) was measured using a digital top-loading electronic weighing balance.   Results: The value of the exponent b in the LWR for H. vittatus was 2.984, indicating negative allometry (b<3). The exponent value of O. niloticus in the LWR was 3.04 (b>3) implying positive allometry. The r2 values for H. vittatus and O. niloticus were 92.3% and 97.3% respectively, indicating that there was a high degree of positive correlation. The condition factor for both fish species were greater than 1.60 implying good physiological conditions for both fish species. Conclusions: This study provides preliminary information on length-weight parameters of O. niloticus whose data was previously not available in the take.