Connectivity, migration, Anguillid eels.


Human land-use activities often affect the quality, quantity and habitat of freshwater ecosystem, which need to be carefully managed to ensure their integrity and provision of services is sustainable. In South Africa, legislation has established resource-directed measures to attain a sustainable balance between the use and protection of water resources. These procedures have been implemented in most of South

Africa’s nine water-management areas, resulting in new legislation to protect these resources. Unfortunately, very little protection has been afforded to river connectivity maintenance and fish migrations. Water storage and flow regulation for agriculture and other resource use activities, 610 formal dams and ,1430 gauging weirs have been constructed that act a partial or complete barriers to fish migration on river ecosystems. The Western Indian Ocean (WIO) Anguillid eels (Anguilla spp.) are long distance catadromous migratory fishes that use both marine and inland ecosystems to complete their life cycles. As they occupy both environments, these eels are particularly vulnerable to marine and freshwater derived threats, and act as ecological indicators of the ecological integrity of riverine, estuarine and oceanic environments. Globally, Anguillid eels have a high socio-economic value and are targeted for commercial and subsistence fisheries. They are proposed to have the highest economic value per weight of any fish. Anguillid eels satisfy a providing function in term of food but also in terms of recreational, cultural and spiritual values. Unfortunately, little is known to the contribution of eels to subsistence fisheries along the coast of the WIO region, and thereby the contribution of these migratory fishes to the livelihoods of vulnerable African human communities is left hanging. The aim of the study is to assist the migratory pathway of Anguillid eels throughout the WIO regions and discuss migration and connectivity stressors of these eels.


Acosta, A. A., Netherlands, E., Retief, F., de Necker, L., du Preez,

L., Truter, M., … Smit, N. J. (2020). Conserving freshwater

biodiversity in an African subtropical wetland: South Africa’s

lower Phongolo river and floodplain. In J. Kideghesho (Ed.),

Managing wildlife in a changing world (pp. 5–26). London, UK:


Anderson, S. M., & Landis,W. G. (2012). A pilot application of regional

scale risk assessment to the forestry management of the

Upper Grande Ronde watershed, Oregon. Human and Ecological

Risk Assessment: An International Journal, 18(4), 705–732.

Ansara-Ross, T. M., Wepener, V., Van Den Brink, P. J., & Ross,

M. J. (2012). Pesticides in South African fresh waters. African

Journal of Aquatic Science, 37, 1–16.

Apitz, S. E. (2012). Conceptualizing the role of sediment in sustaining

ecosystem services: Sediment-ecosystem regional assessment

(SEcoRA). Science of the Total Environment, 415,


Ashton, P. J., Turton, A. R., & Roux, D. J. (2006). Exploring the

government, society, and science interfaces in integrated water

resource management in South Africa. Journal of Contemporary

Water Research & Education, 135(1), 28–35.

Ayre, K. K., & Landis,W. G. (2012). A Bayesian approach to landscape

ecological risk assessment applied to the Upper Grande

Ronde watershed, Oregon. Human and Ecological Risk Assessment,

, 946–970.

Beckvar, N., Dillon, T. M., & Read, L. B. (2005). Approaches

for linking whole-body fish tissue residues of mercury or DDT

to biological effects thresholds. Environmental Toxicology and

Chemistry, 24, 2094–2105.

Bouwman, H., Coetzee, A., & Schutte, C. H. J. (1990). Environmental

and health implications of DDT-contaminated fish from

the Pongolo flood plain. African Journal of Zoology, 104, 275–

Bouwman,H.,Yohannes,Y. B.,Nakayama, S. M. M.,Motohira,K.,

Ishizuka,M., Humphries, M. S.,…Ikenaka, Y. (2019). Evidence

of impacts from DDT in pelican, cormorant, stork, and egret

eggs from KwaZulu-Natal, South Africa. Chemosphere, 225,

–658. https://doi.org/10.1016/j.chemosphere.2019.03.043

Breen, C. M., Dent, M. C., & Mander, M. (1998). The Pongolo

River floodplain and its people: Past, present and future. Paper

presented at the International Conference on Sustainable Rural

Development, 12 February 1998, Salzburg, Austria.

Breen, C. M., Furness, H. D., Heeg, J., & Kok, J. (1978). Bathymetric

studies on the Pongolo River floodplain. Journal of the

Limnological Society of Southern Africa, 4, 95?100.

Brown, C., Joubert, A., Tlou, T., Birkhead, A., Marneweck, G.,

Paxton, B., & Singh, A. (2018). The Pongola Floodplain, South

O’Brien, Smit, and Wepener

Africa–part 2: Holistic environmental flows assessment. Water

SA, 44(4), 746–759.

Coetzee, H. C., Nell, W., Van Eeden, E. S., & De Crom, E. P.

(2015). Artisanal fisheries in the Ndumo area of the Lower

Phongola River Floodplain, South Africa. Koedoe, 57, 1–6.

Coke, M., & Pott, R. M. (1971). The Pongolo floodplain pans.

Newsletter of the Limnological Society of Southern Africa, 16,


Coke, M. (1970). The water requirements of the Phongolo floodplain

pans.Water Year 1970. Paper delivered at the Convention

onWater for the Future, 16–20 November 1970, Pretoria, South


Colnar, A. M., & Landis, W. G. (2007). Conceptual model development

for invasive species and a regional risk assessment case

study: The European green crab, Carcinus maenas, at Cherry

Point, Washington USA. Human and Ecological Risk Assessment,

, 120–155.

Cook, R. B., Suter, G. W., & Sain, E. R. (1999). Ecological risk

assessment in a large river-reservoir: 1. Introduction and background.

Environmental Toxicology and Chemistry, 18, 581–588.

Cooke, A. S. (1972). The effects of DDT, dieldrin and 2,4-D on

amphibian spawn and tadpoles. Environmental Pollution, 3,


Cooke, A. S. (1979). The influence of rearing density on the subsequent

response to DDT dosing for tadpoles of the frog Rana

temporaria. Bulletin of Environmental Contamination and Toxicology,

, 837–841.

Cormier, S. M., Smith, M., & Norton, S. (2000). Assessing ecological

risk in watersheds: A case study of problem formulation

in the Big Darby Creek watershed, Ohio, USA. Environmental

Toxicology and Chemistry, 19, 1082–1096.

Costanza, R., Fioramonti, L., & Kubiszewski, I. (2016). The UN

Sustainable Development Goals and the dynamics of wellbeing.

Frontiers in Ecology and the Environment, 14(2), 59–59.

Department ofWater Affairs and Forestry. (1998). NationalWater

Act (Act 36 of 1998). Pretoria.

De Solla, S. R., Bishop, C. A., Pettit, K. E., & Elliott, J.

E. (2002). Organochlorine pesticides and polychlorinated

biphenyls (PCBs) in eggs of red-legged frogs (Rana aurora) and

northwestern salamanders (Ambystoma gracile) in an agricultural

landscape. Chemosphere, 46, 1027–1032.

De Necker, L., Neswiswi, T., Greenfield, R., van Vuren, J. H. J.,

Brendonck, L., Wepener, V., & Smit, N. J. (2020). Long-term

water quality patterns of a flow regulated tropical lowland river.

Water, 12, 37.

Department ofWater and Sanitation (DWS). (2014). Resource directed

measures: Reserve determination study of selected surface

water and groundwater resources in the Usuthu/Mhlathuze

water management area. Pongola Floodplain – EWR Report.

Report produced by Tlou Consulting (Pty) Ltd. Report no:


Dickens, C., Smakhtin, V., McCartney, M., O’Brien, G., & Dahir,

L. (2019). Defining and quantifying national-level targets, indicators

and benchmarks for management of natural resources

to achieve the sustainable development goals. Sustainability,

(2), 462.

Dube, T.,Wepener, V., van Vuren, J. H. J., Smit, N., & Brendonck,

L. (2015). The case for environmental flow determination for

the Phongolo River, South Africa. African Journal of Aquatic

Science, 40(3), 269–276.

Dube, T., De Necker, L., Van Vuren, J. H. J., Wepener, V., Smit,

N. J., & Brendonck, L. (2017). Spatial and temporal variation

of invertebrate community structure in flood-controlled tropical

floodplain wetlands. Journal of Freshwater Ecology, 32(1),


Dube, T., Pinceel, T., De Necker, L., Wepener, V., Lemmens,

P., & Brendonck, L. (2019). Lateral hydrological connectivity

differentially affects the community characteristics of multiple

groups of aquatic invertebrates in tropical wetland pans in

South Africa. Freshwater Biology, 64, 2189–2203.

Evans, S. W., & Bouwman, H. (2000). The geographic variation

and potential risk of DDT in the blood of pied kingfishers from

the Northern KwaZulu-Natal, South Africa. Ostrich, 71, 351–

Griggs, D., Stafford-Smith, M., Gaffney, O., Rockström, J., Öhman,

M. C., Shyamsundar, P., … Noble, I. (2013). Policy: Sustainable

development goals for people and planet. Nature,

(7441), 305.

Hayes, E. H., & Landis, W. G. (2004). Regional ecological risk assessment

of a near shore marine environment: Cherry Point,

WA. Human and Ecological Risk Assessment, 10, 299–325.

Heeg, J., & Breen, C. M. (1982). Man and the Pongola floodplain.

A report of the Committee for Inland Water Ecosystems National

Programme for Environmental Sciences. Report No. 56,

CSIR, Pretoria, South Africa.

Heeg, J., & Breen, C. M. (1994). Resolution of conflicting values

on the Pongolo River floodplain (South Africa). In B. Patten, S.

Jorgenson, & Dumont (eds.), Wetlands and shallow continental

water bodies (pp. 303–359). Vol. 2. SBP Publishing, The Hague,

The Netherlands:

Heeg, J., Breen, C.M.,&Rogers, K. H. (1980). The Pongolo Floodplain:

A unique ecosystem threatened. In MN. Bruton & KH.

Cooper (Eds.), Studies on the ecology of Maputaland. Durban,

South Africa: Rhodes University, Grahamstown and the Natal

Branch of the Wildlife Society of Southern Africa.

Heeg, J., & Breen, C. M. (1994). Resolution of conflicting values

on the Pongolo River floodplain (South Africa). In B. Patten,

S. Jorgenson, & S. Dumont (Eds.), Wetlands and shallow continental

water bodies (pp. 303–359). The Hague, The Netherlands:

SBP Publishing.

Hines, E. E., & Landis, W. G. (2014). Regional risk assessment of

the Puyallup River watershed and the evaluation of low impact

development in meeting management goals. Integrated Environmental

Assessment and Management, 10, 269–278.

Jaganyi, J., Salagae, M., & Matiwane, N. (2008). Integrating floodplain

livelihoods into a diverse rural economy by enhancing cooperative

management: A case study of the Pongolo floodplain

system, South Africa. WRC Report No. 1299/1/08, Water Research

Commission, Pretoria, South Africa.

Jiang, Q. T., Lee, T. K. M., Chen, K., Wong, H. L., Zheng, J. S.,

Giesy, J. P., … Lam, P. K. S. (2005). Human health risk assessment

of organochlorines associated with fish consumption in a

coastal city in China. Environmental Pollution, 136, 155–165.

Kleynhans, C. J. (2007). Module D: Fish Response Assessment Index

in river EcoClassification: Manual for EcoStatus Determination

(Version 2). Joint Water Research Commission and Department

of Water Affairs and Forestry report. WRC Report

No.TT 330/08, Water Research Commission, Pretoria, South


Landis,W. G. (2005). Regional scale ecological risk assessment: using

the relative risk model. Washington, DC: CRC Press.

Landis, W. G., & Thomas, J. F. (2009). Regional risk assessment as

part of the long term receiving water study. Integrated Environmental

Assessment and Management, 5, 234–247.

Landis, W. G., Markiewicz, A. J., Ayre, K. K., Johns, A. F., Harris,

M. J., Stinson, J. M., & Summers, H. M. (2017). A general

risk-based adaptive management scheme incorporating the

Bayesian Network Relative Risk Model with the South River,

Virginia, as case study. Integrated Environmental Assessment

and Management, 13(1), 115–126.

Landis,W.G.,&Wiegers, J. A. (2005). Introduction to the regional

risk assessment model using the relative risk model. InW. Landis

(Ed.), Regional scale ecological risk assessment using the relative

risk model (pp. 11–36). Boca Raton, FL: CRC press.

Landis, W. G., & Wiegers, J. K. (1997). Design considerations

and suggested approach for regional and comparative

Risk Assessment Framework for Floodplain Management 27

ecological risk assessment. Human and Ecological Risk Assessment,

, 287–297.

Landis, W. G., Ayre, K. K., Johns, A. F., Summers, H. M., Stinson,

J., Harris, M. J.,…Markiewicz, A. J. (2017). The multiple stressor

ecological risk assessment for the mercury-contaminated

South River and Upper Shenandoah River using the Bayesian

Network-Relative Risk Model. Integrated Environmental Assessment

and Management, 13, 85–99. https://doi.org/10.1002/


Lankford, B., Pringle, C., Dickens, C., Chhotray, V., Mander, M.,

Goulden, M., et al. (2010). ‘The impacts of ecosystem services

and environmental governance on human well-being in the

Pongola region, South Africa’, Working Paper, University of

East Anglia and Institute of Natural Resources, Norwich, UK

and Pietermaritzburg, South Africa.

Lankford, B., Pringle, C., Dickens, C., Lewis, F., Mander, M.,

Chhotray, V., & Quayle, L. (2011). Hydrological modelling of

water allocation, ecosystem services and poverty alleviation in

the Pongola floodplain, South Africa. Journal of environmental

planning and management, 54(9), 1237–1260.

Matthews, N., & McCartney, M. (2018). Opportunities for building

resilience and lessons for navigating risks: Dams and the water

energy food nexus. Environmental Progress & Sustainable Energy,

(1), 56–61.

McCartney, M., Janganyi, J., & Mkhize, S. (2003). Comprehensive

options assessment: The Pongolo. United Nations Environment

Programme, dams and development project (DDP) comprehensive

options assessment of dams and their alterations,

UNEP DPP, 35–39.

Merron, G., Bruton, M., Lalouviere, D., & La Hausse, P. (1993).

Changes in fish communities of the Phongolo floodplain, Zululand

(South Africa) before, during and after a severe drought.

River Research and Applications, 8(4), 335–344.

Merron, G. S., Bruton, M. N., & La Hausse De Lalouviere, P.

(1993). Implications of water release from the Pongolapoort

Dam for the fish and fishery of the Phongolo floodplain, Zululand.

Southern African Journal of Aquatic Science, 19(1–2),


Murray, K., & Claassen, M. (1999). An interpretation and evaluation

of the US Environmental Protection Agency Ecological

Risk Assessment Guidelines. Water SA, 25, 513–518.

Nakamaru, M., Iwasa, Y., & Nakanishi, J. (2003). Extinction risk

to bird populations caused by DDT exposure. Chemosphere,

, 377–387.

Netherlands, E. C., Cook, C. A., Kruger, D. J. D., Du Preez, L.

H., & Smit, N. J. (2015). Biodiversity of frog haemoparasites

from sub-tropical northern KwaZulu-Natal, South Africa. International

Journal for Parasitology: Parasites and Wildlife, 4,


Nkhata, B., Breen, C., Hay, D., & Wilkinson, M. (2017). Property

rights, institutional regime shifts and the provision of freshwater

ecosystem services on the Pongola River floodplain, South

Africa. International Journal of the Commons, 11(1), 97–118.

O’Brien, G. C., & Wepener, V. (2012). Regional-scale risk assessment

methodology using the relative riskmodel (RRM) for surface

freshwater aquatic ecosystems in South Africa. Water SA,

, 153–165.

O’Brien, G. C., Dickens, C., Hines, E., Wepener, V., Stassen, R.,

Quayle, L.,…Landis,W. G. (2019). A regional-scale ecological

risk framework for environmental flow evaluations. Hydrology

and Earth System Sciences, 22(2), 957–975.

Pahl-Wostl, C., Charles Voeroesmarty, A. B., Janos, B., Rockström,

J., & Alcamo, J. (2013). Towards a sustainable water future:

Shaping the next decade of global water research. Current

Opinion in Environmental Sustainability, 5(6), 708–714.

Phaka, F. M., Netherlands, E. C., Kruger, D. J. D., & Du Preez,

L. H. (2017). A bilingual field guide to the frogs of Zululand.

Pretoria, South Africa: South African Biodiversity Institute.

Poff, N. L., Richter, B. D., Arthington, A. H., Bunn, S. E., Naiman,

R. J., Kendy, E., … Henriksen, J. (2010). The ecological limits

of hydrologic alteration (ELOHA): A new framework for

developing regional environmental flow standards. Freshwater

Biology, 55(1), 147–170.

Pollino, C., & Hart, B. (2008). Developing Bayesian network models

within a risk assessment framework. Paper presented at

Forth biennial meeting of iEMSs International Environmental

Modelling and Software Society, Barcelona, Spain (pp. 372–


Pollino, C., White, A., & Hart, B. (2007). Examination of conflicts

and improved strategies for the management of an endangered

Eucalypt species using Bayesian networks. Ecological

Modelling, 201, 37–59.

Rebelo, L. M., McCartney, M. P., & Finlayson, C. M. (2010). Wetlands

of Sub-Saharan Africa: Distribution and contribution of

agriculture to livelihoods. Wetlands Ecology and Management,

(5), 557–572.

Schuijt, K. (2002). Land and water use of wetlands in Africa: Economic

values of African wetlands. International Institute for

Applied Systems Analyses (IIASA) Interim Report. IIASA,

Laxenburg, Austria, IR-02-063 Copyright © 2002 by the author(

s). Retrieved from http://pure.iiasa.ac.at/6723/

Schuyt, K. D. (2005). Economic consequences of wetland degradation

for local populations in Africa. Ecological economics,

(2), 177–190.

Smit, N. J., Vlok,W., Van Vuren, J. H. J., Du Preez, L., Van Eeden,

E., O’Brien, G. C., & Wepener, V. (2016). Socio-ecological system

management of the lower Phongolo River and floodplain

using relative risk methodology. WRC Report No. 2185/1/16,

Water Research Commission, Pretoria, South Africa.

Statistics South Africa. (Stats SA). (2011). Census 2011. Retrieved

from http://www.statssa.gov.za/census2011/Strategy.asp

Statistics South Africa. (Stats SA). (2014). Statistics by place:

KwaZulu-Natal. Retrieved from http://beta2.statssa.gov.za/


Suter, G.W. (1993). Ecological risk assessment. Chelsea, MI: Lewis


Thomas, J. (2003). Integration of a relative risk multi-stressor risk

assessment with the NCASI long-term receiving water studies

to assess effluent effects at the watershed level, Leaf River,Mississippi.

Technical Bulletin No. 867, National Council for Air

and Stream Improvement Research, Triangle Park, NC.

Thompson, L. A., Ikenaka, Y., Yohannes, J. B., van Vuren, J. J.,

Wepener, V., Smit, N. J.,…Ishizuka,M. (2017). Concentrations

and human health risk assessment of DDT and its metabolites

in free-range and commercial chicken products from KwaZulu-

Natal, South Africa, Food Additives & Contaminants: Part A,

(11), 1959–1969.

Tockner, K., & Stanford, J. A. (2002). Riverine flood plains:

Present state and future trends. Environmental Conservation,

(3), 308–330.

Volschenk, C. M., Gerber, R., Mkhonto, M. T., Ikenaka, Y.,

Yohannes, Y. B., Nakayama, S., … Smit, N. J. (2019). Bioaccumulation

of persistent organic pollutants and their trophic

transfer through the food web: Human health risks to the rural

communities reliant on fish from South Africa’s largest

floodplain. Science of the Total Environment, 685, 1116–

Wepener, V., Smit, N. J., Covaci, A., Dyke, S., & Bervoets, L.

(2012). Seasonal bioaccumulation of organohalogens in tigerfish,

Hydrocynus vittatus Castelnau, from Lake Pongolapoort,

South Africa. Bulletin of Environmental Contamination and

Toxicology, 88, 277–282.

Wade, M., O’Brien, G. C., Wepener, V. & Jewitt, G. (2021). Risk

assessment of water quantity and quality stressors to balance

the use and protection of vulnerable water resources. Integrated

Environmental Assessment and Management, 17(1), 110–130.

O’Brien, Smit, and Wepener

Wepener, V., Van Dyk, C., Bervoets, L., O’Brien, G., Covaci, A.,

& Cloete, Y. (2011). An assessment of the influence of multiple

stressors on the Vaal River, South Africa. Journal of the Physics

and Chemistry of the Earth, 36, 949–962.

Wiegers, J. K., & Landis,W. G. (2005). Application of the Relative

Risk Model to the Fjord of Port Valdez, Alaska. In Regional

scale ecological risk assessment using the relative risk model (pp.

–90). Boca Raton, FL: CRC Press.

Wolmarans, N. J., Du Preez, L. H., Yohannes, Y. B., Ikenaka,

Y., Ishizuka, M., Smit, N. J., & Wepener, V. (2018). Linking

organochlorine exposure to biomarker response patterns

in Anurans: A case study of Müller’s clawed frog (Xenopus

muelleri) from a tropical malaria vector control region. Ecotoxicology,

(9), 1203–1216.

Wolmarans, N. J., Bervoets, L., Meire, P., & Wepener, V. (2020).

Current status and future prognosis of malaria vector control

pesticide ecotoxicology and Xenopus sp. Reviews of Environmental

Contamination and Toxicology, 252, 131–170.

Yohannes, Y. B., Ikenaka, Y., Ito, G., Nakayama, S. M. M.,

Mizukawa, H., Wepener, V., … Ishizuka, M. (2017). Assessment

of DDT contamination in house rat as a possible bioindicator

in DDT-sprayed areas from Ethiopia and South Africa.

Environmental Science and Pollution Research, 24, 23763–



How to Cite

O’Brien`, G. and Van der Merwe, A. (2022) “RIVER CONNECTIVITY AND EEL MIGRATIONS”, Egerton University International Conference. Available at: https://conferences.egerton.ac.ke/index.php/euc/article/view/208 (Accessed: 17 April 2024).



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