Dry season fish survival in isolated pools and within sand-beds in the Mzingwane River, Zimbabwe

Abstract

Four isolated pools in the otherwise dry Mzingwane River, Zimbabwe, were sampled in December 1985 and a total of 4 547 specimens of 23 species were collected. The dominant species, by number, were Chiloglanis paratus, followed by Barbus toppini, Mesobola brevianalis and Labeobarbus marequensis; the dominant species in terms of biomass were Oreochromis mossambicus, followed by Clarias gariepinus, Tilapia rendalli, Labeo cylindricus and L. marequensis. Most individuals of the larger species in the pools were juveniles, suggesting the potential importance of pools as dry-season refuges. Circumstantial data on fish surviving under the sand during the dry season were corroborated and the importance of thixotropy as a means by which they could be trapped within the sand-beds, is described.