JUST DON'T EAT THEM

While you’d be crazy to eat one of these trout, I’ve been dining out on the idea of them since the start of the project. Their ability to survive and adapt to the impact of the human species on their environment epitomises the indivisibility of the human/natural relationship. If I need to explain the project I reach for the trout: we’re in their gills and livers; we’re in the genes that control their ability to absorb oxygen. The trout appear to be a ‘natural’, part of the landscape, something worth seeking out to wonder over, but they’re no more natural than the sludgy bacteria that live in the copper mine waste in the settling tanks at Great Wheal Seton: they’re here because they’ve adapted to us. In a way, they’re as much a part of the mining heritage of this landscape as the Cornish engine houses on either side of the valley.

When I was dreaming up plans to write about the Red River, I went along to a meeting with marine biologists from Exeter University and Plymouth Marine Lab and, mentioning my interest the river, was introduced to Dr Jamie Stevens from Exeter University who’d been researching its brown trout population alongside populations in other West Country rivers. He wanted to find out how trace-element pollution from the mining industry impacted rivers like the Red River and the nearby River Hayle by causing small genetic changes in the fish populations that might disrupt behaviour, altering ‘dominance hierarchies’, so that, as he put it, ‘the fittest individuals are not necessarily the ones that pass on their genes’.

Of the findings made by Jamie and his team, there were a couple that felt particularly relevant to the project. They’d found that the trout in the Red River and the Hayle were unique subspecies which had evolved to tolerate the toxic heavy-metal burdens present in both rivers, as well as, in the case of the Red River, the low visibility caused by the red iron-oxide precipitates of acid mine drainage. The other discovery, which struck me as even more remarkable, was that, in the case of the River Hayle, and to lesser extent the Red River, stretches of water were so toxic as a consequence of water entering from mine adits that trout populations were unable to cross them by ‘holding their breath’. The fish were effectively trapped in pockets of flowing water, which, according to Jamie, ‘contained a phenomenal burden of heavy metals’. I was astounded by the idea that flowing water might contain invisible barriers, that there were zones in the river no fish could make it through.

Jamie discovered the genetic distinctiveness of these populations of trout by recreating the toxicity of both rivers in the lab, and then introducing fish from ‘clean’ rivers into the simulated water, along side fish from the polluted rivers that had spent time in clean water so that they might have the opportunity to flush out the metal stored in their livers. What he discovered was that a trout from, say, the clean River Fowey, had a ‘hugely detrimental response’, whereas the fish from the polluted rivers, which had held onto their load of heavy metals during their time in the clean water, didn’t have a problem; in other words, they weren’t just loaded up with the poisons, they were specifically adapted to cope with it in their bodies. At various time-points during the process, fin clippings and gills samples were taken and the genes analysed. It turned out that the Foey fish were desperately trying to ‘switch on various genes’ to cope with the polluted water, and particularly those genes concerned with oxygen transfer, as their new toxic environment was ‘buggering up their gills’. By contrast, the native fish didn’t change; they were perfectly at home: they were already switched on to survive through adaptation.

Jamie and his team selected rivers for their comparative study from the South West to avoid mistaking genetic differences resulting from the effects of metal pollution, with other ‘geographic, evolutionary phylogenetic characteristics’. This allowed for an element of ‘control’ to the experiment, as far as any river, even one rising on the other side of the watershed, can form a matched pair. I understood this best when Jamie explained the next stage of his team’s research. He wanted to find out how old the trout populations in the Red River were, and, as a consequence, where they had come from. Given that Cornish rivers were not glaciated during the last ice age, it’s quite possible that they have been living in the river for a lot longer than, say, the brown trout in a Yorkshire river, which had to be recolonised by trout from central Europe after the ice melted. It is also likely that they originate from the rivers that wound their way through the landscape now occupied the English Channel. If this is the case, then the trout in the Red River could be really ‘ancient’, and their adaptation to their environment part of a long-standing interaction its specific water qualities, which, even pre-mining, would have contained heavy metals leaching out from the rock. What we don’t have an answer to, is the proportion of metal pollution that has come from the mines and the proportion that naturally comes from the rocks in the catchment area. Whatever the balance between ‘natural’ and ‘manmade’, the trout in the Red River have survived for centuries in the near zero visibility of its red colouration. I like the idea that these are fish that have had to live, predominantly, by their other senses; after all, this is a project that seeks to open up the river as a sonic presence as much as a visual. It also makes me wonder about the effects of having vision restored and of being more visible.

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From the angle I was looking into the pool it seemed to hover in the air above its shadow: a Red River brown trout, a slit of darkness pulsing in glassy water. I felt I might get close, so quiet had the place made me become. But my foot slipped and the trout ricochetted off in terror around the pool, in and out of the shade and silt, before it found the down-stream exit. It could only have been the span of my hand in length, but it instantly gave the river a shiver of life that extended all along its length. They really did exist. There was enough life to support this complex predator; and where there was one there must be more in the inaccessible morass and boggy woods the river makes as it winds across the bottom of Newton Moor towards Carn Arthen and Brea. Perhaps salmon and sea trout once made it up this far before the tin extraction began, the mouth of the river was straightened, and the many culverts and leats and mechanisms for controlling and harnessing water were installed along its length. The pool seemed perfect for spawning; a place of ancient returns; the haunt for a water spirit. But of course nothing about the Red River’s course is ancient, even this area has been worked over endlessly and the woods in the valley bottom have grown up within living memory; for all I know, the trout pool may only be there because of the velocity with which an upstream culvert feeds the stream that feeds the pool.