Managing river connectivity and fish migration in a water stressed country: considerations from South Africa

A vulgarization of the scientific publication: O’Brien et al., 2019 “River connectivity and fish migration considerations in the management of multiple stressors in South Africa.” Marine and Freshwater Research, available on request for free (celine@riversoflife.co.za) or here.

*All opinions within this piece are that of the author’s (Celine Hanzen) and do not necessarily represent the opinions of her collaborating author’s in the peer review piece above.

While providing numerous valuable goods and services, some of them being irreplaceable, freshwater ecosystems are one of the most endangered ecosystems at a global level. In some regions of South Africa, water scarcity is an everyday problem (remember, Cape Town almost ran out of water in 2018!), for people, industry as well as the flora and fauna that depends on freshwater. In South Africa, we have an ambitious “National Water Act” that considers the need for an “ecological reserve”, which is the reserved flow required for the health of the ecosystem health. It means that if you build a dam, you need to make sure (on paper) that there will be enough water downstream for the fish and flora to be in a healthy state. The lack of water is unfortunately increasingly getting worse via pressure from different economic factors (industry, mining, agriculture, urban human population growing etc…), making it difficult to actually meet the ecological reserve requirements. On top of this, even more pressure comes from land use change but also water regulation schemes (these include, water transfer between catchments for instance. All of these uses, and pressure represent major threats to the wellbeing on the aquatic ecosystems of South Africa. Basically, the law is great, it is just not really being implemented.

On a very sad note, South Africa has recently been listed as one of the worst performing countries (142 out of 180) in the world and even within Sub-Saharan Africa (21 out of 46) according Global Environmental Performance Index assessment. This assessment takes into account Ecosystem Health and Vitality which include water quality, quantity as well as fish and fisheries (among many other indicators of ecosystems wellbeing).

South Africa holds a high diversity of landscape due to different eco-regions and climates. Photos courtesy of Celine Hanzen & Camille Fritsch
South Africa holds a high diversity of landscape due to different eco-regions and climates. Photos courtesy of Celine Hanzen & Camille Fritsch

 THE ROLE OF RIVER CONNECTIVITY

River health and the ecosystem services it provides (drinking water, fish, etc…) are essentially linked to the wellbeing of its basin and therefore the connectivity between the different reaches, streams, ponds, wetlands and other water bodies. For example, building a dam can have two main impacts: (1) The fragmentation of the river habitat which can lead to negative effect on fish and other species in terms of demography, genetic and even behavior. (2) The modification of the natural hydrological regime which can modify the habitat, impact the animal communities and also impact the transport of sediment and substrate. All these effects can lead to indirect impacts, such as change in the natural macro invertebrates and fish communities or the installation of invasive alien species. You can also learn more about African eels in a previous article on BioWeb, here.  

The Thukela, an important river of South Africa, mostly free flowing and harboring a variety of migratory fish species including 3 African Freshwater eels. 
The Thukela, an important river of South Africa, mostly free flowing and harboring a variety of migratory fish species including 3 African Freshwater eels.
Two South African migratory fish species, the African Mottled Eel (left) and the African Sharptooth Catfish (right). Photos courtesy of Celine Hanzen
Two South African migratory fish species, the African Mottled Eel (left) and the African Sharptooth Catfish (right). Photos courtesy of Celine Hanzen

When it comes to the impairment of river connectivity, migratory fish species are particularly at risk and they are actually considered twice as likely to become endangered than their non-migratory counterparts. This is an issue as they are key/vital species and thus components of aquatic ecosystems which they occupy and regulate, not only that but they also contribute to the subsistence, recreational and spiritual activities of humanity. Let’s take the example of Freshwater eels (Anguilla spp): they are long distance catadromous species (they were born far away at sea but spend most of their life in the rivers). In some parts of South Africa (Eastern Cape) they are actually the only top predator in the rivers! This gives them a very unique position in the ecological process. Another example of the importance of migratory fish is the fact they represent an important source of protein for human populations. Historically, many subsistence fishermen have relied on seasonal migration of fishes, African Shartooth Catfish in Lake Sibaya as well as cyprinids (like the yellow fishes) in the Phongolo flood plain or by the San people in the Senqu River. In terms of recreational value, South Africans are very passionately into their fishing: the recreational fishing industry has been estimated at an annual value of US$9,5 million in 2008. 

The connectivity between the sea, estuary and river is also usually overlooked. It is however necessary for many species including our beloved freshwater eels. Here, the Umgeni River Mouth in Durban. Photo courtesy of Camille Fritsch
The connectivity between the sea, estuary and river is also usually overlooked. It is however necessary for many species including our beloved freshwater eels. Here, the Umgeni River Mouth in Durban. Photo courtesy of Camille Fritsch

FISH PASSAGE IN SA

Solutions exist! Unfortunately for our migratory fishes, the interest is very low in South Africa. Only about 60 fish passes can be found in the country, 20% are deemed to be functional, 33% ineffective and the rest have not been evaluated. In comparison, over 600 dams and over 1400 gauging weirs can be found in the country and represent total or partial barriers to migration for many fish species. It’s also important to note that only small barriers have been fitted with these passes, none of the major dams are currently equipped with such structures. It seems that a new wind is slowly coming through as the SA department of Water and Sanitation has initialized the procedures to include fish passage for new dams and weirs. Unfortunately, fish passage is pretty new in South Africa and the design is still in the hands of engineers with very limited inputs from experienced aquatic scientists, but we are very slowly getting there.

On the other hand, Kruger National Park is currently busy removing unnecessary dams. So there you go, there is hope for our fishes!

Video of dam removal in Kruger : https://web.facebook.com/WorldFishMigrationDay/videos/1907008595989968/

PROTECTION OF THE WATER RESOURCES IN SA

As said, South Africa has a great law, the National Water Act that states that water is a scarce and precious resource that belongs to all the people of South Africa. The Act protected the rights of all people to have water as a basic need, but also the need of the ecosystems to be sustainable. It also recognizes that all water on the planet is connected, but sadly does not address river connectivity, fish migrations and the threats that could impact them.

Due the many threats, the majority (57%) of all river types, including main stem and tributaries, in South Africa are now in a threatened or unsustainable ecological state. Worse, when looking at the state of main stem rivers, many (46 %) of them are actually classified as severely modified or critically endangered. This high prevalence of endangered ecosystems is obviously not sustainable and should be addressed urgently, but the current action regarding these issues is inadequate.

WHAT CAN YOU DO?

Let’s not be all doom and gloom, there are many things you could (and should) be doing, wherever you are in the world.

  • Join a river or a beach clean-up (or better still, organize one!)
  • Participate or organize a World Fish Migration Day event (here)
  • Join a Nature Conservancy in your area,
  • Educate yourself (you’re reading this article, you get 10 points!) and others,
  • Do not litter (and correct/educate people who do),
  • Refuse, Reduce, Reuse, Recycle and Rot (yes, there are 5 R’s now),
  • Volunteer anywhere you can, on conservation and research projects,
  • Join a Citizen Sciences group,
  • Use water sparingly and smartly,
  • Think about water costs behind all the products you’re buying (think local, seasonal, organic),
  • Put pressure on local, regional and national government to adopt better policies and implement them,
  • Adopt a new motto: WWGD?! What would Greta (Thunberg) Do?
  • Spread the love for rivers and fish,
  • Be creative and brainstorm, these are just some options there are many more available and everyone should be encouraged to think of even more.

If you want to learn more about fish migration and you don’t want to read all these long and boring scientific publications… you should have a look at the “Sea to Source” book, available as a free pdf online here

The team proudly doing some marketing for the book launch of Sea to Source. Photo courtesy of Kerry Brink
The team proudly doing some marketing for the book launch of Sea to Source. Photo courtesy of Kerry Brink

As a research group, we are involved in outreach and education and we make a point in giving talks and writing popular articles like this one. We also try to organize events (not enough much more needed and planned for the future!) to raise awareness – For example, we did organize a reverse (going up the current!) kayak race in 2018 with St Anne’s School in Pietermaritzburg, South Africa and we always welcome any invitations to come and talk about fish and rivers in local schools (throughout SA).

Invite us and let’s connect people, fish and rivers. Photos courtesy of rivers of life team.

Celine Hanzen
About Celine Hanzen 2 Articles
Celine Hanzen is a PhD candidate in aquatic ecology at the University of KwaZulu-Natal, South Africa. She's had many experiences in the field of conservation, ecology and management of natural resources before moving to South Africa in 2016. She has a B.Sc in Biology and M.Sc in ecology and biodiversity with additional training in environmental management and international cooperation.

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