ECO ACTUALITY: Aliens In Our Midst – Balancing The Act

WORDS: Prof. Paul Skelton  IMAGES: Supplied

In this account I try to bring another perspective and various elements to consider into the discussion of the management of alien species in the natural environment.  I do so on being challenged by the editor in the light of my new book on freshwater fishes in southern Africa.  In the book I present alien invasive species (defined as being species introduced by human agency into an ecosystem from which they are not naturally present and becoming established and self-sustainable) in a neutral light as elements present in southern African inland waters.

I am, of course, fully aware of the conflicting and controversial arguments around, especially, alien sport fishes in natural waters. It is not my intention to stoke those fires in any way – rather just to present my perspective as a scientist with an abiding interest in the evolutionary history, biology and biogeography of indigenous southern African fish species.

I am also a student of the cultural history of freshwater fishes in southern Africa – from the exploration and discovery of the fauna to the modern-day human interaction and management of the fauna.  This naturally embraces an evaluation of the conservation status of the species and the factors that threaten their continued existence – I conducted the first assessment of the conservation status of our freshwater fishes in 1977 and followed that up with a ground-truthing account in 1987.  Since then, the situation for evaluating threatened species has become much more intense, defined and benchmarked on an international scale by the IUCN.  In South Africa this process has been taken to fully international standards through the official national agency SANBI. A recent assessment was published in 2023 (Chakona et al., 2023).      

My point of departure for alien sport fishes is the well-taken standpoint that history is as it is, and one cannot turn back the clock. This is especially clear after the 100 or so years since the introduction of the major angling species in question, carp, trout (both brown and rainbow) and three of the four bass species in our waters. It also holds true for the later introduction of ‘Florida bass’ now considered a separate species on its own account. So essentially this means we have to deal with issues that exist at this point in time and not get lost in arguments about the rights and wrongs of history.

The second point for me is that all these major angling species do have value for us in terms of their economic and cultural values – by which I mean that the healthy and strong angling industry and community of participants derive considerable economic benefit and recreational value from the presence of these alien angling species.  We need to put that into the context of human existence and the overall wellbeing and essence of the South African economy. While this is an important consideration it is not the only one in the cooking pot and it needs to be balanced against the other factors, including that of the impacts and costs of these introduced alien sport fishes. 

This is the core of my third consideration.  Given the remarks in the editor’s challenge around singling out alien fishes for regulation I also need to point out an essential difference between alien invasive sportfishes and the whole gamut of aliens in our midst, both plants and animals, that have been introduced deliberately or accidentally, for agriculture and commerce.  The difference is that the invasive sportfishes are present in the (comparatively unrestrained) natural environment whereas agricultural introductions are under strict control and management in designated agricultural systems (farms and plantations). Generally domestic and agricultural aliens are farmed, i.e. bred and harvested under a production system and are not free to run amok and feed and breed where they like.  Furthermore, it needs to be clear that, apart from carp in our context, sportfishes like bass and trout are basically predators and have direct impact on other creatures in the rivers and dams and that they therefore enter and impact the natural food-chains that exist. The equivalent for agriculture is hard to find – canned lions and tigers?

It is in this area of the impact of invasive alien sportfishes where the campfire discussions get most heated. On the one side the point is often made – well, so what if the aliens eat a few insect larvae or small fishes (ghieliemientjies), nobody knows or even cares about them.  The important thing (it is claimed) is that these aliens need a healthy environment in which to live – and we (the anglers) fight to ensure that remains so.

Keeping the aquatic environment healthy is certainly a cause we can all subscribe to – especially when the damaging factors are pollution of different kinds – on the largest and significant scales being from big industry, mines, agriculture and, of course, concentrations of humans in cities and urban areas. And, in this respect, when we think about it, is the reality that actually we are facing ourselves as the agents of environmental impact – whether we are farmers or industrialists or employees and workers mostly living in urban environments where we all contribute to the impact – so we need to be careful just how loud we rant about this issue. 

Then there is the argument around the significance of those ‘insignificant species like insects and ghieliemientjies’.  Essentially, we are all extremely ignorant of the ecological and environmental roles that many aquatic organisms play.  Repeatedly detailed studies that are made point to the essential linkages that exist in the natural world – ‘everything is connected’.  From time to time when foreign elements are introduced to a stable system the impacts are profound – a living example is the introduction of Nile perch into Lake Victoria – the ecological disruption that followed affected even the human populations living around and exploiting the lake’s productivity.

I remember a story told me by my mentor, Dr Rex Jubb, many years ago. Rex’s father was, in the early 20^th Century, a magistrate in the delightful town of Prince Albert on the northern flanks of the Swartberg in the Cape. He was an avid trout angler and together with local enthusiasts introduced trout to the mountain stream that fed the town’s reservoir. As the trout became established and expanded their range downstream, they eliminated the redfin minnows (rooivlerkies) that inhabited that stream.  With the minnows gone the algae bloomed in the canal (small furrow) feeding water from the river into the town reservoir and the canal was eventually clogged up.  This caused the municipality to have to clear the blockages at some cost.  This key role of rooivlerkies in the food web or food-chain of Cape rivers has been more recently studied and explained by scientists. The point here is that even ghieliemientjies can have significant functional roles to play in a healthy ecosystem.

In the debate on the impact and management of alien sportfishes I have not yet seen an argument around the heritage of our natural or indigenous fishes. By heritage I mean the inherited environment to which we belong, that which is part of our own being and nature – the natural world for which we as South African are temporary participants and beings.  So, I will try and make and illustrate this point for what it is worth.

My inaugural professorial lecture at Rhodes University was titled “An African Heritage of fishes”. In essence my new book speaks to this heritage for freshwater fishes, of the richness of the fauna in its evolutionary and biogeographic history and to the discovery and interaction of humans with fishes in the natural environment.  This heritage includes alien fishes as you will note. Those elements are here because part of our society saw them as being a positive value, and part of our society still accepts that value. Our indigenous fishes have been here far longer than even humans have existed on the planet, some far longer than most if not all other vertebrate lineages! And freshwater fishes, by virtue of their complete dependency on freshwater, are tied to the land in a much more dependent state than are terrestrial organisms. Their history and distribution reflect the very history of the land itself. This makes them a very deep and special heritage factor – they embody the story of our land like few other vertebrates do.  But by being aquatic organisms our exposure and appreciation of their world and existence is far less obvious than most of nature around us. Thus, most of us hardly know our fishes and those who do know some fishes, like anglers, only know a few prized target species – and then, to stretch the point, some of those species at the top of the pile, are alien sport fishes. To know and love something is to care for it. How can we care for something we don’t even know?

So, it does not surprise me to find that, by and large, anglers don’t often dig deep into the conservationist argument that there is another side to the sport? In some cases, where alien sportfishes impact indigenous species to a point where the latter are threatened with existence then that is the case where I feel we are obliged to take restorative action including if necessary, the active removal and restriction of alien species from natural habitats. There are a few excellent examples of where this has taken place and the whole community, including anglers, have participated. In the Western Cape the ‘Saving Sandfish’ and the Breekkrans restoration projects are two examples.  The growing experience is that when the various threats to indigenous species are understood reasonable people tend to come together for what is the right thing to do.

In essence I could summarise the situation by saying what I personally would like to see is that ‘them and us’ become ‘us’ as far as our heritage of fishes is concerned. Then with a common sense of ownership and values we will all fight the same battle – we will find the right space and place for all our interests, whether that be angling or hunting or hiking or whatever. Part of this dream would be simply being more tolerant of the needs of others. Another part would be working together to ensure a sustainable future for all, even ghieliemientjies! 

-Paul Skelton, December 2024.  

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