Item Details

Title: Observations on limnological conditions associated with a fish kill of Oreochromis niloticus in Lake Chivero following collapse of an algal bloom

Date Published: 2006
Author/s: Lindah Mhlanga, Jenny Day, Moses Chimbari, Nqobizitha Siziba and Gertrud
Data publication:
Funding Agency : Water Research Fund for Southern Africa
Copyright/patents/trade marks: East African Wild Life Society
Journal Publisher:
Affiliation: University Lake Kariba Research Station, PO Box 48, Kariba, Zimbabwe, 2Freshwater Research Unit, Department of Zoology, University of Cape
Town, Rondebosch 7701, Western Cape, South Africa, 3Lake Kariba Fisheries Research Institute, PO Box 75, Kariba, Zimbabwe and 4University of
Lund, Department of Ecology/Limnology, Ecology Building, S-223 62 Lund, Sweden
Keywords: algal bloom, fish kill, Oreochromis niloticus


Possible causes of deaths of Oreochromis niloticus in Lake
Chivero were examined in relation to changes in limnological
conditions monitored over a 25-month period. The
fish deaths coincided with the collapse of an algal bloom
that had developed and builtup in the lake for 8 months.
Chlorophyll a and dissolved oxygen increased to average
concentrations of 42.4 lg l)1 and 10.9 mg l)1 respectively
prior to the collapse of the bloom. Dissolved oxygen
decreased when the bloom started to die off and coincided
with the fish deaths when the average surface dissolved
oxygen concentration in the lake was 3.9 mg l)1 and was
at a depth of 5 m <2 mg l)1. Mortality probably resulted
from depressed oxygen levels caused by the high oxygen
demand from the massive algal die-off and released algal
toxins. This is the first time that die-off of algae has been
linked to fish-kills in Lake Chivero as occurs in other
hypereutrophic systems.