Western Indian Ocean Marine Science Association

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Slippery resource in peril: Ecology of Western Indian Ocean Anguillid eels and their contribution to sustainable fisheries and livelihood along the East Coast of Africa.

A. Basic Facts

In this study our specialist scientists and endeavoured to elucidate aspects of the biology, ecology and social value of eels in the WIO region, and determine the risk of multiple stressors affecting the life cycle ecology of the WIO Anguillid eels and their contribution to subsistence fisheries in the region. To achieve this our regional representation of the WIO eel distribution included teams in Kenya, Mozambique and South Africa and has been extremely valuable. We have been able to address questions through a plethora of research tasks including evaluating aspect of the recruitment of eels and how eels use estuaries and lowland rivers to recruit into the African interior, we have looked as various biology and ecology aspects of our eels as they migrate into our rivers. We have unpacked where eels occur, how they are doing, what they are doing and importantly how they contribute to the livelihoods of vulnerable African communities. We have also considered the multiple stressors that threaten the wellbeing of our eels and through a regional scale ecological risk assessment we have considered the probable synergistic effect of multiple anthropogenic stressors on to our WIO eels.

Our research has contributed to an improved understanding of the distribution of WIO eels, and importantly how different eels dominate different areas of the estuaries and rivers of the WIO region. We have also discovered and described life-cycle attributes for the WIO region and unfortunately demonstrate how our WIO Anguillid eels have been negatively affected by numerous anthropogenic stressors resulting in significant reductions in distributions throughout the region.

Our research has also uncovered illegal trade in live Anguillid eels in South Africa and Mozambique that generates up to US$7500/annum to dedicated fishermen. These same eels harvested by one fishermen could be worth more than US$35000 as a delicacy in Asia. We do not unfortunately know how many fishers are involved in this trade but know that a larger secretive inform industry exists that is threatening the sustainability of our WIO eels in Mozambique and South Africa. Similar activities have been uncovered in Kenya. The eels of the whole region also contribute to food security for many vulnerable African communities and have historically contributed to cultural beliefs and values. Unfortunately our research has identified regions where eel migrations have been disrupted and how communities are unable to benefit from the ecosystem services associated with eels. We have also demonstrated how the anguillid eel associated cultural heritage of communities in southern Africa is being eroded and how beliefs associated with Anguillid eels in the region are drifting into folklore. Our people need to have eels live in the estuaries and rivers where they used to live in, before we built dams that affect their migrations.

Our risk assessment identified dams and over-harvesting of eels as the major hazards or threats that have resulted in the wellbeing of WIO eels being in a moderate to high risk state throughout the region. These results are alarming as all populations throughout the region in all countries are being affected by anthropogenic stressors. Without refuge areas and health populations of the four Anguillid eels in any part of the WIO region the entire WIO populations are threatened. Our risk assessment described the risk associated with the maintenance and escapement of eels into the Indian Ocean as the most vulnerable part of the life-cycle history of our WIO eels. While the sustainability of our eels is threatened and that this possibly results in ecological, social and economic losses to African communities in the region we are not considering eels in our regional Integrated Water Resource Management. It is not too late we can re-establish connectivity of our rivers, we can conserve our eels, we can sustainably use our eels and enhance the social and economic benefits they offer to all people of the WIO area, but we need to do something soon, because in the last few decades the wellbeing of our eels has deteriorated significantly.

Unfortunately our research has not solved all of the questions we posed entirely and we have increased our list of research questions pertaining to the sustainable protection of an use of our WIO eels, we hope that this foundational research which is the first of its kind for the eels of the WIO region as a whole will contribute to improved conservation action and the management of our valuable eels and the water resources of the WIO region they, and we depend on.

 

What were the problems the project intended to address?

The goal of this study was to understand the use and conservation needs of WIO Anguillid eels and contribute to the sustainable management of these fishes in the region. The study aims to determine the risk of multiple stressors affecting the life cycle ecology of the WIO Anguillid eels and their contribution to subsistence fisheries in the region. For the study, we included case studies in Kenya, on the northern extent of the distribution of WIO eels and Mozambique and South Africa representing the middle and southern extent of the WIO Anguillid eel distribution.

Study Sites:

The study area included the WIO distribution of the four Anguillid eels along the east coast of Africa. The study included four priority study areas namely the Athi-Galana-Sabaki and Ramisi Rivers in Kenya, the Limpopo and Incomati Rivers in South Africa and Mozambique and the Thukela River in South Africa. All of the river basins along the WIO region of Africa and Madagascar have the potential to contribute to the populations of the four African Anguillid eels and as such were considered in the regional scale risk assessment of multiple stressors to the eels. For the risk assessment, 60 risk regions or major sub-basins and or regions of sub-basins have been evaluated to identify potential stressors to the Anguillid eels following the social and ecological assessments, so that the risk of multiple stressors to the life-cycle attributes of the eels can be established. This approach includes the four priority catchment areas considered in the study where the confident risk of the multiple stressors to the eels is available and the rest of the distribution risk regions where comparatively less certain risk projections of multiple stressors to the eels are available.

   i. Project Partners

Kenya Marine and Fisheries Research Institute (KMFRI), University of Mpumalanga, University of Kwazulu Natal, University of North West.

   ii. Project Duration 2019-2022
   iii. Project Site(s)
   iv. Project Country Kenya, Mozambique, and South Africa
   v. Budget US$ 441,684
B. Project Objectives

The following objectives were proposed for the study:

  1. Undertake a literature review of the known diversity, distributions, biology, ecology and socio-ecological importance of WIO Anguillids.
  2. Establish hypotheses of the biology and ecology of WIO Anguillids and their use as a targeted fisheries species from existing literature and specialist solicitations from fisheries managers/scientists and ecologists in the WIO region.
  3. Characterise the timing and prevalence of the recruitment of Anguillid eels into the Athi and Ramisi Estuaries (Kenya), the Incomati Estuary (Mozambique/South Africa) and Thukela Estuary (South Africa), and threats to these migrations.
  4. Characterise the timing and prevalence of the escapement of Anguillid silver eels from rivers back into the sea, including some initial preliminary marine migration routes and behavioural ecology information (Athi, Inkomati and Thukela Estuaries).
  5. Evaluate the contribution that WIO Anguillid eel fisheries make to local community livelihoods and any commercial fisheries opportunities.
  6. Undertake a regional scale ecological risk assessment of multiple stressors to the wellbeing of Anguillid eel populations throughout the WIO.
  7. Review water resource use, protection and fisheries regulations in the region and make recommendations to address ecological, social and economic management of Anguillid eels and associated river connectivity and fish migrations.
C. Expected Results
D. Project Activities
E. Publications

A total of ten M.Sc and Ph.D students have completed their studies through this WIOMSA project and received operations expenses and bursaries from the project. We expect all of these students to publish their data chapters regarding Anguillid eels in peer-review scientific journals.

Below is a list of the running titles from the students’ theses.

  1. Africa, L., Hanzen, C., Burnett , M., Downs, C.T. Recruitment of African glass eels (Anguilla spp.) into the Thukela River, South Africa. MSc Student at the University of Kwazulu Natal, South Africa.
  2. Burnett, M., Nkomo, M., Van Der Merwe, A., O’Brien., G.C., Hanzen, M., Downs, C. Ecological risk assessment of multiple stressors affecting eels and the vulnerable human communities who depend on them within the Thukela Catchment, South Africa. Contributing member from the University of Mpumalanga.
  3. Dlamini, V., Vetina, A. and O’Brien G.C. The contribution of WIO Anguillid eel fisheries to local fisheries, livelihood, socio-economic and cultural aspects in different parts of the Incomati Basin in South Africa and Mozambique. Contributing member from the University of Mpumalanga.
  4. Erasmus, H., Herselman, S. and Wepener, W. Preliminary report on metal concentrations in muscle and liver tissue of two eel species from the Incomati River. PhD Student from the North West University, South Africa.
  5. Gitonga LM, Kihia CM, Mlewa CM, Kariuki C, Tembo KJ, Mbaru EK, Hazen C. Occurrence and recruitment of juvenile Anguillid eels into the Sabaki etuary, Athi river, Kenya, MSc student at Egerton University, Kenya.
  6. Kaadzo, T.J., Kihia, C., Mbaru, E. The socio-economic value of eels and river fishery along Kenyan east flowing rivers. MSc Student from Egerton University, Kenya.
  7. Kaadzo, T.J., Kihia, C., O’Brien, G., Kitaka, N. Assessment of biotic interactions between catadromous Anguillids with sympatric riverine ichthyofauna along Athi-Galana-Sabaki and Ramisi Rivers, Kenya. MSc student at Egerton University, Kenya.
  8. Kaiser, A., Van Der Merwe, A. and O’Brien, G.C. Environmental DNA (e-DNA) evaluation of the potential distribution of Anguillid eels in the Limpopo and Incomati Basins, southern Africa. PhD Student from the University of Mpumalanga.
  9. Kariuki, C.W., Kihia, C.M., O’Brien, G., Donde, O., Hanzen, C., Mbaru, E.K., Tembo, J.K. Occurrence, recruitment and maturation of catadromous Anguilla eels under differing anthropogenic impacts, in two east flowing Rivers of Kenya. Principal Investigator from Egerton University, Kenya.
  10. Kariuki, C.W., Kihia, C.M., O’Brien, G.C., Donde, O., Tembo, J.K., Hanzen, C. and Mbaru, E.K. Habitat use and trophic interactions among four sympatric occurring anguillid eels along the Athi and Ramisi Rivers of Kenya. PhD Student from Egerton University, Kenya.
  11. Muchiri, Z., Kihia, C., Mbaru, E., Karori, S. Heavy metal contamination among Anguillid eels in two Kenyan east flowing rivers. MSc student at Egerton University, Kenya.
  12. Nkomo, M., Hanzen, C., Burnett, M., Downs, C. The contribution of WIO Anguillid eel fisheries to local fisheries, livelihood, socio-economic and cultural aspects within the Thukela Catchment, South Africa. MSc Student from the University of Kwazulu Natal, South Africa.
  13. O’Brien, G., Hanzen, C., Mbaru, E., Burnett, M., Van der Merwe, A., Kaiser, A., Kihia, C. An ecological risk assessment of multiple stressors affecting the Western Indian Ocean Anguillid eels. Principal Investigator at the University of Mpumalanga, South Africa.
  14. Truter, M., and Smit, N. Evaluation of the parasite communities of eels from the lower Incomati River, South Africa. PhD Student from the North West University, South Africa.
  15. Van Der Merwe, A., Kaiser, A. and O’Brien, G.C. Impact of dams on the distribution and decline of Anguillid eels in the Incomati Basin, South Africa. PhD Student from the University of Mpumalanga.
  16. Van der Merwe, A., Kaiser, A., Hanzen, C., O’Brien, G.C. A regional scale Risk Assessment of the Incomati Catchment, southern Africa, and the associated drivers affecting Anguillid eels using the Relative Risk Model. PhD Student from the University of Mpumalanga.
  17. Vetina, A., Van Der Merwe, A, Kaiser, A. and O’Brien, G.C. Anguillid eels and the fish communities of the lower Incomati River and Estuary, Mozambique. MSc Student from University of Mpumalanga, Mozambique.
F. Students Supported by the Project
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