A life in a day
Neil Collins
Ephemera danica is quite a girl. Nearly four inches long, with great wavy things at both ends, she looks pretty scary, and when they are blundering about by the thousand in the air above your head, you might think you're about to star in an entomological version of Hitchcock's The Birds.
E. danica is better known as the mayfly, an insect so absurd that it hardly seems worth the evolutionary trouble. It's the one that makes a fool of the wiliest trout, and an expert of the clumsiest fly-fisherman. The mayfly spends two years scuttling about on, or under, the bed of a suitable river, until one spring day it decides to break for the surface. If it gets there, it splits open and sails downstream until its wings are dry enough to fly. Flight, and sex, are all it has on what is laughably called its mind. It can't attack anything, not even a leaf, since it has no mouth. Having found its lifelong partner, it flies upstream, lays eggs (if female) and dies — all in one day.
It took me some time to work out the point of all this, but it's obvious when you're told. The larvae lack the strength to swim against the current, so without some way of getting upstream, they would all eventually be swept out to sea. Nature, in its magnificently Heath Robinsonian way, has constructed the whole elaborate performance of two years' preparation for one ecstatic day purely to get round this problem. It's odd, then, that there are some parts of the magnificent River Kennet where myriad mayfly blot out the sun with their fertility dances, and others where they are almost unknown, often only a few miles distant. Blessed indeed are those of us with access to those parts which E. danica does reach.
The first beneficiaries of these juicy bundles of flying protein are the swifts, who literally snap up (you can hear them) the earliest mayflies as they struggle from the water. At this stage, the trout seem to ignore them. This is a puzzle; the fish depend on eating whatever the stream brings them. They must see these sitting ducks, sailing down the river like miniature galleons, but they don't seem to grasp that they are food.
The trout's little brain has to register things on the surface as they drift into its restricted field of view. In the couple of seconds before they go by, it must compute whether it's worth the bother to swim up to investigate. Trout are both curious and lazy, so it's a tough call. If it's an unfamiliar shape which may not be edible, the snap decision is probably not to bother.
The nearer the fly is to the fish, the less the energy cost of taking a look, which is why a well-cast dry fly can bring a trout to the surface even if it's not feeding. Once they've actually tasted a mayfly, they're hooked, so to speak. It's the trouty equivalent of chocolate truffles. When there's a big hatch going on, with mini-galleons appearing on the water surface as if by magic, they become almost reckless with enthusiasm, often jumping out of the water to catch a fly that's just achieved lift-off.
This is the famous 'duffers' fortnight', when it's supposed to be harder to avoid catching fish than actually to do so. The best mayfly days are, like Cambridge May Balls, in June. This is the moment for the piscatorial pusher to offer the innocent punter his free fix. By the time the poor sap realises fly-fishing is really quite hard, and often heart-breaking, the habit is ingrained, and there's another addict on the books.
If it were not unpredictable, the pastime would be dull indeed. If every time you cast, the fly landed perfectly, the fish rose as if in a textbook and, after a fine fight, ended up on the bank, the true flyfisherman would think he'd gone to hell rather than heaven. The conditions can be perfect, the keeper regaling you with tales of how last night the water was boiling with rising fish and yet tonight the river seems dead — and in the middle of duffers' fortnight, too. You just can't tell.
You can't tell, either, whether fish feel pain, that almost metaphysical question where the answer depends on the definition as much as anything else. No suitable receptors in the brain, say the no-painers; very suitable receptors in the mouth, say the how-would-you-like-it lot. If they are right, it's an odd sort of pain that encourages the fish to run in the direction which makes it worse.
I suspect that, even if it were conclusively proved that fish do feel pain, we would still try to catch them; it certainly doesn't seem to do them any lasting damage, as big old coarse fish get caught time and again, and still come up looking pretty healthy. I prefer to catch only what I can eat, or give away to my family, voracious trout-eaters of all ages. It's much better for them than fish fingers — in the long run, it's better for the fish, too.
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