Assessment of Environmental Impacts of Cage Aquaculture on Lake Volta of Ghana

250 Pages·2016·4.43 MB·English

Kwame Nkrumah University of Science and Technology
Faculty of Renewable Natural Resources
Department of Fisheries and Watershed Management
Kumasi, Ghana

Assessment of Environmental Impacts of Cage Aquaculture
on Lake Volta of Ghana

A thesis submitted to the Department of Fisheries and Watershed
Management in partial fulfillment of the requirements for the award of the
degree of Doctor of Philosophy (Ph.D) in Aquaculture and Environment

BY
Anthony Yaw Karikari

June, 2016
Kwame Nkrumah University of Science and Technology
Faculty of Renewable Natural Resources
Department of Fisheries and Watershed Management
Kumasi, Ghana

Assessment of Environmental Impacts of Cage Aquaculture
on Lake Volta of Ghana

A thesis submitted to the Department of Fisheries and Watershed
Management in partial fulfillment of the requirements for the award of the
degree of Doctor of Philosophy (Ph.D) in Aquaculture and Environment

BY
Anthony Yaw Karikari

June, 2016
Acknowledgements
First and foremost, I would like to thank the Almighty God for His grace and providence.
I would like to express my sincere gratitude to my supervisors and academic
advisersProf. Steve Amisah, Prof. Lindsay G. Ross, Prof. Trevor C. Telfer, Dr. (Mrs.)
Ruby Asmahand Dr. Nelson W. Agbo. I am indebted to them for their help, guidance
and encouragement, insightful comments and the invaluable contribution in shaping this
thesis. My special thanks go to Dr. Daniel Adjei-Boateng, Head, and the entire staff of
the Department of Fisheries and Watershed Management, KNUST for their support and
encouragement throughout the period of the study programme. I would like to thank the
Director and staff of CSIR Water Research Institute, especially personnel in the
Environmental Chemistry and Sanitation Engineering Division for their assistance in
field work and laboratory analyses. I am grateful to the staff of the Institute of
Sustainable Aquaculture, University of Stirling, UK for their great help and making my
stay there enjoyable.
My deepest appreciation is reserved for my wife, Francisca and my family for their love,
patience, understanding and support throughout my study. I am thankful to my Church
members for their inspiration and prayer support. Special thanks to all my friends,
especially Messrs. Emmanuel Akuffo (CSIR-SRI), Andy Quashie (CSIR-IIR), Gabriel
Appiah), Francis Amevenku, Daniel Amoah of (CSIR-WRI) for their immense help.
I am grateful to the aquaculture farmers and the community members for answering my
probing questions with patience. I am exceptionally grateful to Mr. Lars Lynge of West
African fish farm and Mr. Lee Kuo Rong of Lee farm for allowing for their farms to be
used as study sites and also providing data and boat for the study.
Finally, I would also like to acknowledge the financial support by the Royal Society
under the Leverhulme Africa Award, without which the PhD, study would not have been
possible.

i
Dedication

Dedicated
To
My wife, Francisca Nyamekye Karikari
and
my daughter, Ruth Maame Dufie Karikari
ii
Abstract
In recent years, tilapia cage farming has become important aspect of commercial fish
production in Lake Volta and the number of the cage culture establishments (now 467)
continues to expand in the multipurpose lake. Cage farms release nutrients that can
cause pollution to water and sediment quality. However, there is paucity of information
on the impact of cage culture on the lake’s environment. Consequently, a study was
conducted from August 2013 to April 2015 at two fish farms in the Lake Volta to assess
the potential impact of cage culture on the environment of the lake.
The study utilized four methods. The first was through structured questionnaire to
gather information on the cage farms. The second method used physico-chemical
analyses of water and sediment following standard procedures. The third method
considered mass balance model to estimate the amount of nutrients discharged from
the cage farms into the environment. The fourth method used Dillon Rigler phosphorus
mass balance model for the prediction of ecological carrying capacities of two selected
farm areas in the lake.
The results from the questionnaire survey on the cage farms revealed that only large
scale farmers have adequate environmental awareness and therefore monitor the water
and sediment quality in their farm areas. The study on the nutrient waste emission from
the cages indicated that 64.8–68.1 % of C, 72.0–75.8 % of N, and 81.0–84.7 % of P of
the total feed input were released into the lake’s environment for each tonne of fish
produced, and only 31.9–35.0 % of C, 24.2–28.3 % of N and 15.3–19.2 % of P were
harvested as fish biomass. Despite the large discharges of particulate and dissolved
nutrients estimated by the mass balance models, physico-chemical water quality
parameters including dissolved inorganic nutrients (NO -N, NO -N, NH -N and PO -P),
3 2 4 4
chlorophyll-a varied temporally and showed no significant differences between the fish
farm sites and the reference sites (ANOVA, p > 0.05). The low impact of the cage
aquaculture could be attributed to the nutrient losses through the outflow at the dam
which was 43.56 km3 per annum (i.e about one-third of the lake’s volume); dispersion of
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the wastes by water currents, consumption of waste by schools of wild fish species
found around the fish cages and also by dilution.
Sediment analysis revealed the sediment texture of all monitoring sites to be sandy clay
loam with moderate impact on sediment quality with respect to organic matter. The total
organic carbon (TOC), total organic matter (TOM), and total nitrogen (TN) content in the
sediment under the cages were significantly lower than those of the reference sites
(ANOVA, p<0.05). The results showed that concentrations of heavy metals in the water
column and sediments were low and within the range of tolerable levels for the lake
ecosystem. The estimated ecological capacities were from 3,697 to 4,621 ty-1 for Farm
A and from 28,322 to 33,042 ty-1 for Farm B zones. The estimated ranges of values are
higher than the present production in the zones. This suggests that more cage culture of
tilapia could be established in the lake without compromising the water quality and the
ecosystem. However, water quality monitoring should be undertaken periodically to
accurately determine the current state of the lake in order to both confirm and refine
predictions, and ensure sustainable cage culture development in Lake Volta. Overall,
the water quality indices (CCME-QI and GWQI) carried out indicted that the lake water
is good and suitable for tilapia production and other ecosystem uses such as irrigation,
recreation and water supply.

iv
Declaration
I hereby declare that this work, submitted to the Department of Fisheries and
Watershed Management of the Kwame Nkrumah University of Science and
Technology, Kumasi, Ghana, for the award of Doctor of Philosophy (Ph.D) is the
result of original work carried out by myself under the guidance of Prof. Steve
Amisah Prof. Lindsay G. Ross, Prof. Trevor C. Telfer, Dr. Ruby AsmahandDr.
Nelson W. Agbo. Any technical and analytical assistance during the experimental
period and citations of other work have been duly acknowledged. I further
declare that the results of this work have not been submitted for the award of any
other degree in the above-mentioned University or any other university
elsewhere or for fellowship considerations.

Kumasi, Ghana, June, 2016 Anthony Yaw Karikari

Certified by…………………………… …………………………….
Prof. Steve Amisah Date
(Supervisor)
Certified by …………………………….
Prof. Lindsay G. Ross Date
(Academic Adviser)
Certified by ……………………………..
Prof. Trevor C. Telfer Date
(Academic Adviser)

Certified by ……………………………. ……………………………..
Dr. Ruby Asmah Date
(Supervisor)

Certified by ……………………………. ……………………………..
Dr. Nelson W. Agbo Date
(Supervisor)

Certified by ……………………………. ……………………………..
Dr. Daniel Adjei-Boateng Date
(Head of Department)
v
List of Abbreviations
AAS: Atomic absorption Spectrophotometer
ANOVA: Analysis of Variance
ARDEC: Agriculture Research and Development Centre
CCME WQI: Canadian Council of Ministers of the Environment Water Quality Index
COD: Chemical Oxygen Demand
CSIR: Council for Scientific and Industrial Research
DO: Dissolved Oxygen
DoF: Directorate of Fisheries
EAA: Ecosystem Approach to Aquaculture
EIA: Environmental Impact Assessment
FAO: Food and Agriculture Organisation of the United Nations
FCR: Feed Conversion Ratio
FFAs: Fish Farm Associations
GDP: Gross Domestic Product
GEPA: Ghana Environmental Protection Agency
GNAP: Ghana National Agriculture Development Plan
GOG: Government of Ghana
GPS: Geographic Positioning System
GWQI: Ghana Water Quality Index
LDCs: Least Developed Countries
LIFDCs: Low Income Food Deficit Countries
MoFA: Ministry of Food and Agriculture
MoFAD: Ministry of Food and Agriculture Development
NCR: National Research Council
NGO: Non Governmental Organisation
NH -N: Ammonia-Nitrogen
4
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NO -N: Nitrite-Nitrogen
2
NO -N: Nitrate- Nitrogen
3
OECD: Organisation of Economic Corporation for Development
PO -P: Phosphate-Phosphorus
4
POC: Particulate Organic Carbon
PON: Particulate Organic Nitrogen
POP: Particulate Organic Phosphorus
PVC: Poly-Vinyl Chloride
SHS: Senior High School
SPSS: Statistical Software Package for Social Sciences
TC: Total Carbon
TN: Total Nitrogen
TP: Total Phosphorus
VRA: Volta River Authority
WRC: Water Resources Commission

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TABLE OF CONTENTS
Acknowledgements .......................................................................................................... i
Dedication ........................................................................................................................ii
Abstract ........................................................................................................................... iii
Declaration ...................................................................................................................... v
List of Abbreviations ........................................................................................................vi
TABLE OF CONTENTS ................................................................................................ viii
LIST OF TABLES .......................................................................................................... xvi
LIST OF FIGURES ........................................................................................................ xix
CHAPTER 1: GENERAL INTRODUCTION ..................................................................... 1
1.1 Background of Study .......................................................................................... 1
1.2 Problem Statement ............................................................................................ 2
1.3 Justification ........................................................................................................ 5
1.4 Research Objectives .......................................................................................... 8
1.5 Thesis Approach ................................................................................................ 8
1.6 Fisheries and Aquaculture ................................................................................. 9
1.6.1 Overview of Global Cage Culture .............................................................. 11
1.6.2 Aquaculture in Africa ................................................................................. 14
1.6.3 Cage Culture Production Systems ............................................................. 15
1.7 Environmental Impacts of Cage Aquaculture. ................................................... 15
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