The Beautiful River Hiding A Massive Ecological Crisis ¦ Mighty Rivers.

With its historic cities and picturesque countryside, the middle reaches of this mighty river are well known to sightseers. Much less well known but crucial for my investigation is another of the Danube's great fish, an elusive creature known as the hooken. Now this is a landlocked relative of the salmon and it grows to the size of a man But since World War II, this fish has become little more than a memory, it's like a ghost fish. I'm wondering what this says about the river and whether I have any chance at all of seeing this fish. I'm eager to talk to anyone who might remember the hooken. But apart from the occasional commercial barge, this stretch of the Danube is strangely empty. Hoping to find signs of life, I decide to check out the backwaters. The distant ring of an axe draws me on. It's very solid. Are you a fisherman? I start to piece things together. It seems that Janos and his family belong to a tribe of wood carving gypsies. He says he used to carve boats for fishermen who paid him with the fish they caught from the Danube. I'm straining to pick out one fish in particular. But it goes unmentioned. I think I recognize most of those fish, but have you ever seen a hooken? Janos says that when he was a boy, he remembers seeing large sturgeon. But as for the hooken, he's not sure. This is hooken, they just seem to be gone, but don't ask me, I don't know about these things, ask a fisherman. Before I can resume my search, Janos invites me to try out what he says is his last ever canoe. Where do I sit? These days, no one wants a hand-carved boat. This one is destined for a museum. It's very nice. It's very good. I like it. I'll take it. I'll take it. How much? With the hard work done, it's time for a glass of gypsy moonshine. To make room for farms and towns, the Danube's backwaters have almost all been drained. But I've heard about some interesting ponds just off the river. During World War II, dozens of American bombs intended for a Nazi airfield landed harmlessly off target, with intriguing results. This is a wartime bomb crater. It's a window into the groundwater, which continues from here, underneath my feet, all the way to what we normally think of as the river over there, across this flat, open plain. But the real significance of all these bomb craters is that they're now a lifeline for many of the plants and animals that once thrived in the Danube's marshy backwaters. So this is actually a refuge. Bombs are normally destructive, but here they've created something quite important. Back on the main river, my search for the Danube's missing predator is taking me into more densely populated country. Who can afford to have abandoned many of their old haunts because of pollution? But so far, at least, the water seems remarkably clean. When you're in a city, the sounds that you hear tend to be all man-made. There's voices everywhere, there's traffic. But if you come out here, you can actually hear the voice of the river. And looking down, I'm very much aware of the flow of the river, the sheer volume of water that's passing every moment. With so much flow, big rivers have an impressive capacity to clean themselves. This, and the fact that there's no heavy industry around here, should be good news for the Hukon. But has anyone here even heard of this fish? Hello. Oh, hi. This is a good spot here? Yeah, it's actually a famous spot. Budapest city centre is one of the best spots in Hungary. It turns out that Laszlo has been fishing here since he was a boy, and he says there's plenty to catch. Looks like he's even got something. Do you think he chose? Yes, of course. What's the Hungarian name? In Hungarian-English dictionaries, they are called nose carp. Because of that. So the water here is clean? Yes. Normally, it's transparent. Pollution level is very low. Now, there are more predators here. Do you ever see the Hukon here? Have you ever seen it? Oh, the mysterious fish. Sometimes you hear the gossip that somebody caught one over there, and then there is another gossip that someone caught one over there. I have even travelled to distant countries to try to catch it, but I've never seen it in Budapest. It will be my dream. With clean water and no shortage of prey, this stretch of the Danube ticks two big boxes for the Hukon. Yet the only place it lives is in people's dreams. What its absence is telling me about the river is still unclear. One thing I'm getting used to, though, is the near-constant procession of floating juggernauts. There are some people doing something in the bank here. I'm just going to check it out. Come here. Hello. I've seen a similar kind of thing in the Amazon. This is gold panning. Imre tells me he started panning on weekends as a way to relax. But it seems he now has a more romantic objective. What he's trying to do at the moment is make a ring for his girlfriend. He started on that project about six months ago. He reckons another six months, so a year in total to make this ring. Does she know that you're doing this? She doesn't know. So where does she think you're going in all your spare time? She knows that I'm a gold panner, but sometimes I also tell her I'm going to see my parents or something else. There's a little bit of subterfuge going on. At first glance, Imre's search for gold has no connection with my search for the hukon. But in fact, the presence of both depends on the precise flow of the river. Hukon dislike water that's too sluggish. And so does Imre. He needs the current to be a certain speed to carry the gold particles downstream from their source. There's lots of specks, but they are tiny, they are tiny, tiny. What makes Imre's task extra difficult is that nowadays the flow of the river has become unpredictable. He's saying there's a dam that's gone in upriver, and since that happened, it's just changed the river. The panning spots have changed. By next week, the precious gold could have been carried somewhere else. Dams are built for many reasons, not least to improve navigation. But by changing the river's natural flow, I wonder if they're making life hard for the hukon. If you were just an ordinary person, you're looking at a river, you think it's exactly the same. But if this is what you do, you know that something's happened. You don't even have to know about the dam, you just know that something's happened to the flow. And it has to be the same for the fish, too. We don't understand enough about them, but if a dam can so change the flow of a river that somebody panning for gold can detect it, then the hukon have got to be affected. They are indicators. They indicate that we've done something to the river that I need to understand. Maybe I'll find the real thing in neighbouring Austria. I'm going to a place that was once at the heart of the hukon's range. Superficially, there's not much wrong with the Danube here. And on close inspection, it looks better suited to hukon than anywhere I've seen so far. It's narrower, but it's also faster. The water's clearer and almost certainly there's a higher oxygen content. Now, from my knowledge of the salmon family, it's this kind of water where they're much more likely to feel at home. Hukon are active site hunters that thrive in clean, fast-flowing watercourses. That's why their presence is a kind of gold standard for a healthy river. This is a nice little bit of slack off the main push. I mean, the main current is running very, very strong and fast. But in here, it's the kind of place that fish might be lurking. What I'm trying to do is let the lure sink to the bottom and then just twitch it, let it sink again, twitch it, let it sink again, twitch, sink. One thing that can't be blamed for the hukon's absence is overfishing. As a species, hukon have never been commercially exploited. And here, at least, recreational anglers are required by law to put them back. Since nothing is biting, though, I decide to ask around. What fish are you after? Have you fished here on the Danube many years? Since? Yeah. What about hukon? Do you see them at all in the river now? He says he's never seen any hukon in the river. But he's got a contact who sounds intriguing. You have a friend who's a specialist? Can you give me his name and maybe how do I find him? And where is he? Okay. So that's just down a little way here? Nice, thank you. No fish, but some interesting information. It seems I need to go and speak with a certain Mr Fisher. Maybe I'm actually going to see the Danube's elusive ghost fish. The aptly named fishers are eager to show me something very special. Look at that. What an amazing fish. For decades, hukon have hardly been seen in the Danube. Just so fantastic. I've never seen hukon before and here they are. They're almost in touching distance. What we do here, we're keeping them. Joe and his dad are hukon fanatics. For years, they've dreamt of re-establishing a wild population in the Vakal Valley. This irrigated pond holds their precious breeding stock. That's nice. Here we go. There, there, there, there. Look at this. I never thought I would get to hold one of these in my lifetime. That's a very, very rare fish and they are just magnificent. Breeding and raising baby hukon is a time-consuming business that costs the fishers a lot of money. The fact that you are doing it as private individuals, purely out of interest and passion, that really is something special. Definitely. If we don't do it, nobody else is doing it. Bringing the hukon back would be extraordinary. But for that to happen, don't we need to understand why it vanished in the first place? So this big decline in the hukon, why do you think that was? That the biggest problem is straightening. In the 17th and 18th century, the government wanted to do shipping a little easier and now it's a huge problem. Starting 300 years ago, it seems that large stretches of the naturally winding Danube have been radically re-engineered. Here, let me show you. That's really dramatic. A surprising amount of change. The Red Tea was ideal for hukon, just a lot of bends and curves. When you go further, you see that all the gravel banks and bends are lost. They were the most important thing for the hukon. So it's a conflict between navigation and the breeding of the hukon. And by improving the navigation, it has almost destroyed the breeding conditions for the hukon. Definitely, correct. Remarkably though, I'm told that some of the engineering that destroyed the hukon's breeding grounds has now been undone. And for the fishers, this is creating a unique opportunity. When the Danube was straightened for shipping, side branches like this were sealed off. But several have now been reconnected and these revived backwaters make an ideal nursery for young hukon. The temperature right here is perfect. It's very clear. There's no waste from ships plus there's no fishing allowed. So they can grow up here very safely. Just as important though, is that the Danube's reopened side branches also have the right conditions for adult hukon to breed. Successful breeding for hukon is about the structure of the riverbed. They need gravel in order to breed. The thing about gravel as opposed to mud or silt is the spaces in between. This allows the water to flow around the eggs, bringing that all-important dissolved oxygen without which those eggs would just die. If you straighten the river, if the flow is too strong, it washes away those gravel beds and you lose the fish. When I first tried to pick up the trail of the hukon back in Hungary, I never imagined that I would see one actually in the waters of the Danube. And here I am, not seeing one. There's 30 or 40 in front of me. This could be the beginning of something very significant. If the hukon story teaches me anything, it's that a tightly controlled river is not wildlife friendly, no matter how pretty it looks. The whole process of control of the river by humans is something which has continued and accelerated even until this day. The thing about rivers is that they're restless, writhing creatures. They keep changing their course. So we lock them in a straitjacket. But the fish don't always like that. Further up the Danube, though, lives an exception, an aquatic invader that's wreaking havoc. In its upper reaches, the Danube is more than 1,500 miles from the sea. But I've heard that this part of the river is being overrun by a saltwater invader. Oh, there we go. Something just pulled. Oh, yes, I've got something. I've got something. I've got one. It may look cute, but according to reports, it's a destroyer. This is a thing called a round goby. This shouldn't be anywhere near here. The goby's natural habitat is on the shores of the Black Sea, amongst rocks. This interesting arrangement of the pelvic fins, that is for sort of holding itself to a rock. To find out more about these tiny invaders, I've arranged to go fishing with biology professor Jurgen Geist. So these gobies, how do they get here? By ship ballast water. They pump in water and automatically suck in eggs or larvae or even adult fish. And when this water gets released at those upstream sites, the gobies enter these areas. So basically, right down in the mouth of the river, they're taking in water just to create stability for the boat. That then comes up here. They let that water go. But it's not just water. There's lots of other stuff in it as well. Exactly. There are very few fish that can easily move from salt water into fresh water. But the gobies can cope very well with fresh water. Today, we're fishing both sides of the river, starting along one of the rare stretches of completely natural shoreline. We will do some electro fishing in this really shallow area. Jurgen's net is in fact an electrode that shocks the water with around 800 volts, enough to stun any fish within six feet. My job is to scoop them up before they recover and swim off. Here we go. It doesn't take long to get some fish. And I'm curious to see what's here. This is really interesting because within this natural stretch, we really exclusively got native species of fish. So no gobies? No gobies. Only native fish, including this trout. This is a young fish. So this habitat is extremely important for the reproduction of those native fishes. So where are all the gobies? The opposite side of the river is also shallow. The big difference is that the bank here is man-made. In between those boulders, those are the spots where they are hiding. Using exactly the same voltage, we quickly fill our bucket with stunned fish. The question is, how many of them actually belong here? Out of all the fish that we caught here, there's just one single native species. That's a chub, isn't it? Yes, but this is only dominated by gobies. We find all size and age classes from the really big adults to those very small ones. This is ideal habitat for them. The tight packed rocks along the banks hold the river in place. For native fish, this straitjacket is an alien environment. But for the gobies, it's home away from home. I have noticed a lot of these banks. How much of the Danube are we talking about? More than 90%. So what effect does this have on the native species? Within the last 10 to 15 years, the entire food web of this upper Danube region has completely changed. It's such a dramatic difference. Hundreds of miles of man-made banks are allowing the invaders to proliferate. And worse still, they're gobbling up the eggs and young of native fish. What I need to know is whether there's anything here that eats gobies. Dusk is often the time when predators stir. And there's one in particular that could be very significant. Just a few feet out, you've got an area that's about 20 foot deep. It's the kind of place where you'd expect to find larger fish. When I think about fish that might be unaffected by man-made banks, my mind turns to a beast that can grow bigger than a man. It's a fish that guards its nest. So any gobies after its eggs would end up on the menu themselves. If it is still here, then I for one will feel a flicker of hope. Here we go, here we go. Yes! Really tight because I don't want the fish running. I just want it. This is strong gear. I just want to get it in. Ah! Oh god, it's still there. It's in close, it's in close. There it is, there it is. Here we go, here we go. This, I'm very pleased to say, is a native species. The Danubian or Wells catfish is an eating machine. This is the apex predator of this part of the river. And think about those gobies. They would just be perfect snacks, not even bite-sized snacks. They wouldn't need to bite them. They just suck them in. For me though, this goby eater is doubly significant. In most of the big rivers in the world now, you won't find iconic species in the main rivers. You've got to go to very remote corners on the river systems. So to get a decent-sized Danubian catfish from the Danube actually feels very good. Perhaps more than any other river in the world, the Danube is one continuous picture postcard. How could anything possibly be wrong? But looking under the surface, what you've got is a very complicated story. This is far from a natural wild river. What makes me hopeful is the continued presence of the Beluga sturgeon, the hookum, and the Danubian whales catfish.