In 1950, a rather surprised angler caught a two metre Zambesi shark at the confluence of the Levuvhu and Limpopo Rivers in South Africa’s Lowveld.
This must have come as a little bit of a surprise, since the nearest ocean, the Indian, is over 400 km away.
The Lowveld is not however, a popular shark-fishing destination. This sort of thing had never happened before and has never happened since. In fact, the Lowveld isn’t well known for its fish at all. With good reason.
There are actually nearly fifty fish living down in the Lowveld. But you are simply almost never aware of them. The water, you see, is just a little on the dirty side. You could park a bright red Sherman tank just one inch below the surface of a Lowveld river, and you wouldn’t be aware of it until you swam into it while desperately trying to get away from a crocodile. And that crocodile should give you a clue as to how many fish there are here.
There are seven permanent rivers in the Kruger Park, the main wildlife area of the Lowveld. In them live several thousand crocodiles. And crocodiles, despite what you see on the Discovery Channel, live mostly of fish, not wildlife documentary hosts. They do pull down the odd land creature, but that’s mostly just the very big ones. And they grow that big on fish.
It’s time for another Lowveld ecosystem post. I have been a little bit slack. I’ve been writing about the Lowveld for over a year now, and I’ve never mentioned the fish. So here goes.
The stupidest fish in the world.
I started off with a shark that had swum further up river than it should have, so let’s carry on in the same vein. I’ve always been fascinated by salmon. We are all so used to the idea of what they do that we don’t stop to think about what a remarkable thing it is. But it really is bizarre. Why? Why would an otherwise perfectly sensible fish, change its shape, give up on that whole eating thing, and leave its perfectly sensible home in the sea to swim up a river, spawn, and die when the sea seems like a perfectly adequate place for all the other fish to spawn and not die?
It would seem, since the salmon’s closest relatives are the trout, that the salmon is a freshwater fish that found it was easier to live in the sea. It just never worked out how to breed there.
No. There are no Salmon in the Lowveld. We do, however, have eels. And eels, like salmon, cannot decide whether to be freshwater fish or sea fish. But they do it the other way around. The eels in the Lowveld are in what is called the feeding stage. They lurk around in that muddy, under-oxygenated water eating crabs and fish for a few years, or indeed decades, until they start to feel an unfamiliar itch. And then they start to swim towards the sea. 400 km away.
This tends to take a while. But the time is not wasted. They use it to change into oceanic fish. They change from motley yellow to sleek, shiny silver. They get bigger and stronger. Their eyes get bigger and their snouts sharper. And then something even more peculiar happens. They lose their ability to eat. Literally. Their digestive systems wither away. They grow reproductive organs instead. And mate. All that remains is for them to swim to the other side of Madagascar to lay their eggs. And disappear.
The eggs drift down to the South African coast where they hatch into tiny, transparent larvae, which is how they drift along until the whiff of fresh water causes them to change into glass eels, at which point they start swimming upriver, changing slowly into the motley yellow Lowveld eels as they go.
And when they get there, they start the whole cycle all over again. It’s all just stupid. I get that it works, but why? Why not evolve to breed in fresh water? It’s warmer, and what’s more, it’s where you are. If you have to go to the sea, if that’s your “thing”, why the hell go round Madagascar? What’s wrong with our own sea? And if the sea is so damn important to you, why not stay there? I’ve heard reliable reports that there are actually fish and crabs there, and the water is cleaner, too.
Eels the world over do this. They head out to the most outlandish places to breed. I’ve actually heard the whole phenomenon blamed on continental drift. By all reports, the continents tend to drift around rather slowly. The theory is that the eels used to follow far more sensible migration routes. As the continents and oceans drifted slowly around the globe, so too did the eels’ final destination. But it never drifted far enough fast enough to warrant the eels sitting up and thinking “You know, this is all getting just a little bit silly”. It just moved a few millimetres a year, if that.
But now it’s drifted quite a long way, and all the other Lowveld fishes laugh as the eel’s eyes start to boggle and he dashes off downstream. To Madagascar.
Nobody laughs at the tigerfish. South Africa doesn’t have many good indigenous angling fish. The fish round here don’t seem to put up the sort of fight that the people who like killing fish enjoy. This guy is an exception.
You can see why. He has the same sleek, muscular body as the trout or salmon. There is, however, just a little bit of a problem at the one end.
Anglers prefer to fight their fish from one end of a long stick with some string tied to it. They do not like to fight their fish inside their boats at the risk of losing their fingers. So to go tigerfish angling you need to take along a special metal fish-holder.
The mystery fish.
This is the Tsiri River.
It flows past my parent’s holiday home in the bush. For about two weeks a year. The rest of the time, it looks like this.
It occasionally comes down in something approaching the biblical flood, but most years it doesn’t rise to anything above ankle height, and flows gently for a couple of days afterwards before disappearing below the sand. Sometimes thirsty elephants will dig holes down to the water for a cool, refreshing drink, and then other animals will use it for a few days before the sand shifts over it again, but for the most part, it looks as dry and unforgiving as the Sahara.
But when it is flowing, something remarkable happens. Fish come swimming up the river. Quite big fish. We used to have great fun chasing after them, splashing through the ankle-deep water and shrieking like banshees. We never actually got one, but we would come pretty close when they powered through the shallows with more than half their bodies exposed, silver flanks glistening in the sun and bright orange fins sticking up like flags. They are called Bushveld Papermouths.
I have no idea where they came from or where they thought they were going, but I cannot help but think that this was not a very smart survival tactic. Maybe they had swum up from the point where the Tsiri River had joined up with a permanent river. Maybe they had spent the long dry spell trapped in a few residual pools.
But it’s where they’re going that really makes me wonder. These aren’t the sort of fish that can survive buried in the mud. The best most of them can hope for is to find a shallow pool that lasts slightly longer than the receding waters, and then watch their new home slowly recede in the sun until the storks and leopards and hyenas move in and pick them off. There ain’t no promised land at the top of the Tsiri River for Papermouths.
You should be getting used to this by now. When it comes to the Lowveld, there’s always a weirdo. But this one is special. I’ve seen all the other fish on this list, but not this one. Almost no-one has. They were only discovered living in a few isolated pans in the Kruger National Park a few decades ago, and have now been introduced in a few more.
Evolution took so long to emerge as a theory because you can’t see it happening. Usually. But if you see a Lungfish, it all makes sense. The lungfish is a very ancient fish, and it appears to be busy evolving into something else entirely. It cannot, you see, breathe underwater. Its swim bladder has evolved into a pair of lungs, and its gills have atrophied to the point where they no longer work. It has a pretty good reason for doing this. In most of its homeland, it lives in swamps where the water can be very poor in oxygen, so it has to rise up and gulp in fresh air. In the Lowveld, it takes things one step further.
It lives in seasonal pans, shallow dents in the surface of the ground that fill with water in the rainy season, but dry out to cracked, concrete-hard scrapes when the rains stop. As the water recedes, the lungfish digs itself a hole in the mud, and there it stays, trapped in the rock-hard dried mud ’til the next rainy season. Breathing.
That’s not all the Lungfish is up to on the evolutionary front. It also seems to have decided to learn to walk. It can swim like an eel, but spends most of its time walking around on the bottom of its pan on a set of creepy, Japanese-animation style tentacle-fins.
I feel a little bit sorry for the Lungfish. In a few million years, it’s going to be ready. It will come strolling up out of the shallows, blinking in the bright sunlight and mentally giving itself a high-five for mastering that whole evolution thing, only to find that all the good spots are taken. And then it will sadly turn around and walk back into the water again, to set about re-evolving functioning gills.
Yes, the fish of the Lowveld have a king. But you can set aside any ideas you have of brave King Arthur clad in shimmering armour. This is a loathsome beast. A goblin king.
It’s called a Sharptooth Catfish. On paper. But we all just refer to it as a Barbel. So what makes it a king? Well, it’s the biggest fish in the Lowveld, for a start, if you don’t count the odd geographically challenged shark. It gets up to 1,4 metres long and weighs about thirty kilograms. There are perennial rumours of enormous man-eating barbel in South Africa’s bigger dams that are reputed to take small children. It’s the closest we can come to our own Loch Ness monster.
But that, as they say in the infomercials, is not all. Barbels are far and away the most widespread fish in the Lowveld. They can live almost anywhere. You find them in rivers and dams, in streams with largish pools, in sewage treatment plants and in sewers themselves, and in those same seasonal pans where the lungfish live. Which makes you wonder how they get around.
Most often, eggs are transported from one place to another on the legs of waterbirds. But they do have another trick up their sleeves. Sharptooth Catfish can walk across dry land. Or rather wet land. On rainy nights, they use two sharp spines to haul themselves up out of the water and crawl their way to another pool. God only knows how they know where they are going. The lungfish must look on with seething envy. They can’t even feel superior about that whole lung thing, either, because barbell can breathe out of water, too, using specially modified gills. Smug bastards.
But wait! That’s not all. Their diet sets them apart, too. Barbel eat everything. Dead or alive, if it’s organic, they will happily chomp it down. They eat fish, crabs, turtles, baby crocodiles, waterbirds, small mammals, seeds, plants, and, if those Loch Ness rumours are to be believed, small children.
Their ability to live anywhere, on anything, leads to one of the bushes great spectacles. When a large pan that is home to several barbell dries out, the barbell do not die. Because they can breathe air, they can survive in the sort of squishy mud that feels good to squeeze between your toes. Or would if it wasn’t full of hideous goblin-fish. But when the pan dries out too much, the barbell have nowhere to run and nowhere to hide. And the predators move in for a feast.
Their ability to live anywhere, on anything might just let them take over the world. Because people have realised that they are pretty damn easy to farm. Most fish farms need to be incredibly carefully managed. You can get away with quite a lot on a barbel farm, though. Throw them in a muddy ditch and dump in all your agricultural waste, and Bob’s your uncle. They breed easily and grow quickly. And they have another advantage, too. In poor and hungry places, where there is no electricity, barbell can be sold live. Take a plastic bucket off to market and you can come home with your dinner so fresh it’s still swimming around.
This is fantastic for us here in Africa, but I see trouble brewing. People are trying to farm them in other parts of the world now, too. This is not smart. A fish that can live anywhere, and eat anything, is not a welcome introduction to any ecosystem anywhere. Throw in the fact that it can physically climb out of the water and wander off, and you’ve got an environmental catastrophe on your hands. Watch yourselves, Australia!
Well that’s it for me. Suppertime. I will not, as I’m sure you will understand, be having fish.