Fishmail: Schrödinger's catfish

December 28th, 2002

I spent yesterday with a group of quantum physicists. It's a long story. And not much of it will be especially interesting to a group of flyfishers, for sure. All I'll say for now is that these guys have to deal with some things that are so bizarre, so astonishingly counter-intuitive, that just thinking about them makes your brain try to escape out of your ears. They just accept that things can be in two places at the same time, for example – indeed, they know that the existence of the universe absolutely depends on it. And they routinely deal with things so infinitesimally tiny that those size 32 midges that take you a week to tie (and that you never use) seem the size of whole planets by comparison. Niels Bohr, a bloke who knew a thing or two about physics, summed it up thus: “If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.”

I was profoundly shocked yesterday even though I hadn't understood it; and that, I suppose, is the nature of shock generally. It made me realise, not for the first time, how many things there are that are pointless for me to try and comprehend, let alone enjoy; football, pineapple and folk music being just three examples. The fact that any kind of universe can exist with these things in it is utterly mysterious to me, but quantum physicists take this sort of thing for granted all the time. So when I tried to explain to them just how peculiar trout are, they just nodded sagely and went back to talking about wave-particle duality and single-photon emitters and cats that were dead and alive at the same time. (Warning: this link contains poetry, and may thus profoundly disrupt the fabric of your space-time continuum).

I felt mildly slighted by this. Not for the first time, I have been worrying about the true oddness of trout a lot recently, and their apparent unwillingness to obey any of the laws of my universe, so their casual acceptance of this was vaguely insulting. How can it be anything other than devastatingly weird that a trout will ignore your finest nymph imitations for hours on end, before deciding to hammer your badly-tied and incompetently presented muddler? Is it not exceptionally cruel that I can spend weeks trying to catch a six-pound brown trout in New Zealand, only for Tom to catch a nine-pounder minutes after he steps off the plane? And most baffling of all, why is it that I keep doing this? All of this can, at some level, be explained by quantum mechanics. I have no idea how. But some things have become clearer to me since my discussions yesterday. For example, one of the basic principles of this quantum stuff is that you cannot observe a quantum event without disturbing its result. This is why Jim Curry never looks at a trout that he is trying to catch, I suspect, and why every time I look in my fly box there are only half the number of flies that I had assumed were there. As soon as you look, something changes.

If you think I'm being flippant here, you're both right and wrong – something else that quantum mechanics has no trouble at all in dealing with. The extent to which our mere presence interferes with our fishy pursuits is about as well understood by most of us as Heisenberg's Uncertainty Principle, but there is no doubt that the moment we step onto the bank of a lake or a river, something weird happens. I went grayling fishing on the Hampshire Avon recently, in conditions that might well be described as impossible – very low water of a clarity that made your average bottle of Gordon's look like a pint of Guinness, accompanied by bright sunshine. From a small bridge, I could see several big fish hovering at the tail of a pool 40 yards or so upstream; time to get down on my hands and knees and anything else that might let me crawl as close to the ground as my less-than-boyish figure currently allows. I am nobody's idea of a crafty mover, but was as careful as I have ever been in sneaking up on a fish; yet by the time I was no more than eight yards closer, the fish had all buggered off, not to return for the rest of the day.

We've all been there, I know. The fact that fish of all kinds have supernaturally tuned self-preservation mechanisms comes as no surprise – especially not when you know that they have Weberian ossicles as a kind of military-grade add-on to their already impressive lateral line equipment. But this was different. These grayling knew I was there long before anything as crass and ungainly as a sound wave got anywhere near them. I suspect that simply bouncing a few photons off them was enough to send them fleeing rapidly to the deep, fast water at the head of the pool.

There's an excellent article by John Bailey in the latest edition of the excellent Waterlog magazine, in which he describes immersing himself in a river and listening out for the sound of fishing tackle hitting the water. It's worth subscribing to the magazine just to read this, because it will change the way you think about the effect your presence by the waterside has on what's happening underneath it. I plan to conduct some experiments of my own with fly lines as soon as the water warms up enough to sustain human life without the aid of a submarine. Until then, I'm back off to see what's happened to that cat. It may be both dead and alive simultaneously, but that won't stop me troubling it for a few handfuls of quantum dubbing – I'm hoping that if there's one thing that will catch me a trout next year, it's a fly that both is and isn't there at the same time. Meanwhile, a very happy New Year to you all – may your seasons in 2003 be bountiful.

Sean Geer ( is a freelance journalist and author. He specialises in ritual humiliation by fish on four continents - most recently in Ireland, where he became the first angler in history to not land a mayfly-caught trout on Lough Corrib in the middle of the mayfly season. A retired seahorse conservationist and self-taught zen origamist, he is currently writing a novel about sex, death and the meaning of fish.

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