International Journal of Aquaculture, 2013, Vol.3, No.4, 11
-
16
http://ija.sophiapublisher.com
11
Research Report Open Access
Impact of Aquaculture on Water Quality in Lake Kariba, Zimbabwe
Beaven Utete
1
,
Letween Mutasa
1
,
Nobuhle Ndlovu
2
,
Itai Hillary Tendaupenyu
2
,
Crispen Phiri
3
,
and Taurai
Bere
1
1
Chinhoyi University of Technology Department of Wildlife and Safari Management, P. Bag 7724, Chinhoyi, Zimbabwe
2
Lake Kariba Fisheries Research Institute, P. O. Box 75/P. Bag 2075, Kariba, Zimbabwe
3
University of Zimbabwe Lake Kariba Research Station, P. O. Box 48, Kariba, Zimbabwe
Corresponding author email:
beavenu@yahoo.co.uk;
Authors
International Journal of Aquaculture, 2013, Vol.3, No.4 doi: 10.5376/ija.2013.03.0004
Received: 25 Jan., 2013
Accepted: 4 Feb., 2013
Published: 21 Mar., 2013
Copyright © 2013
Beaven. This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Beaven, 2013, Impact of Aquaculture on Water Quality in Lake Kariba, Zimbabwe, International Journal of Aquaculture, Vol.3, No.4 11-16 (doi: 10.5376/ija.2013.
03.0004)
Abstract
This study investigated the water quality at the aquaculture effluent discharge points in Lake Kariba. Water samples were
collected at three sites designated site 1 (Crocodile Farm effluent discharge point), site 2 (Fish Farm effluent discharge point) and site
3 (
Control point) from the month of September 2011 to January 2012. Physico-chemical variables (temperature, total dissolved solids,
turbidity, pH, conductivity, nitrates, ammonia, and ortho-phosphate) were measured. Turbidity, total dissolved solids, pH and
conductivity were found to be significantly (ANOVA, p<0.05) high at aquaculture effluent discharge points compared to the control
point. Relative to the World Health Organization (WHO) and Environmental Management Authority of Zimbabwe (EMA-SI)
guidelines for aquatic waters, turbidity, nitrates and ammonia at site 1 and site 2 were found to exceed the maximum allowable limit
(5
NTU), 10 mg/L and 0.05 mg/L respectively while dissolved oxygen was below the minimum allowable limit of 5 mg/L. All other
physico-chemical parameters were within the accepted range at all stations. While the physico-chemical results indicated
deteriorating water quality at the discharge point due to the effluent inflow, the large water volume in Lake Kariba plays an important
factor in diluting aquaculture effluent.
Keywords
Aquaculture effluent; Discharge points; Water quality; Lake volume; Lake Kariba
Introduction
Exponential human population growth, economic
stagnation and food security is becoming a major
concern in developing countries. This population
increase has caused overexploitation of natural
resources such as fisheries resources in lakes and
rivers in the world (World Bank, 2004; FAO, 2007).
To address this overexploitation of wild fish stocks,
Zimbabwe and many other countries are promoting
aquaculture (Songore, 2002).
Aquaculture, the
farming of aquatic animals and plants, has been the
world’s fastest growing food production system for
the past decade, with an average compound growth
rate of 11.6% per year since 1984 (
Tacon, 1999;
Songore, 2002). Over the last decade an increase has
been noted in fish and crocodile farming along Lake
Kariba (Ndebele et al., 2011).
At present fish farming and crocodile farming are
the major aquacultural activities in Lake Kariba
(
Taylor, 2010, Ndebele et al., 2011). Fish farming
concentrates on the production of
Oreochromis
niloticus
fingerlings which are then cage cultured to
market size in the Sanyati basin of the lake (Utete
and Muposhi, 2012). Crocodile farming enterprise
focuses on the production of crocodile skin, with
meat as a by-product (Mugg et al., 2007). These
have both grown over the years to become the
biggest aquaculture enterprises in their different
disciplines in
Africa (Taylor, 2010).
Effluent from
these aquacultural activities is discharged directly
into the lake. The effluent of the two enterprises is of
major concern since release of nutrient rich effluent
from these cultures may lead to eutrophication of the
surrounding systems with negative impacts on the
biodiversity and a change in the physico-chemical
parameters of the receiving water body (Iwama, 1991).
Although the amount of effluent may be relatively
small, their significance is greater if they are highly
toxic,
persistent and mobile or accumulate rapidly in
organisms. The effluent may also lead to localised
eutrophication in inshore waters of the lake. If the
discharge, which is mainly uneaten feed and animal
waste products, is not carefully monitored, it will