Wandle Restoration Part XIII

alevins

Trout tank trilogy: part 2

21 January

The trout eggs started hatching today! There’s an almost-metallic tang in my nostrils as I flip the lid of the aquarium for its morning inspection, with a rim of white foam on the powerhead pump’s aerator, and empty egg-shells wafting round the tank like little white ghosts.

In the spread-out nest of eggs, life is unmistakeably stirring. The hatching-enzymes have been at work, and 10 or 15 tiny alevins are already sinuating slightly on top of the other unhatched ova: more are half-emerged, head-first, struggling to free themselves.

By evening, more than half of them are out, and I’m elated. This is why we’re really cleaning up the Wandle, month in, month out. And it’s not just to add value to people’s homes and views, or make councils happy, or both – but so that little trout can one day live and breed in pure Wandle water, just as they did for tens of thousands of years before humans came along and messed it all up.

It’s a big ambition. But to me at least, each of these tiny hatchlings brings us one step closer to fulfilling it.

23 January

48 hours later, and almost all the eggs have hatched. A cloud of shells encircles the pump, and the nest is filled with a tightly-woven bright red mat of centimetre-long alevins. Totally translucent except for that single, strikingly scarlet vein, each one seems to watch me through huge black eyes – hoping I’ll go away, trusting to strength of numbers to see them through this critical encounter.

Assuming a temperature of about 10 degrees Celsius, these babies’ protruding yolk-sacs should now be enough to nourish them in the gravels and stones for about 5 weeks. During that time, they’ll do their vulnerable best to keep their heads down, self-sustaining, avoiding predators of all kinds.

Naturally wary they may be – but far from frozen with fear, as I discover when I prod the gravel nearby to remove the remaining (very dead) pasty-white eggs. As soon as danger gets too close, there’s a flurry of red in the water, and a flight of alevins scrambles from the tarmac at emergency 45-degree angles. Hard-wired safely procedures in action: baby trout can’t be too careful when a bucket-mouthed sculpin or turkey baster comes calling.

24 January

Researching my February article on Trout in the Classroom for Fly Fishers’ Republic, it’s been immensely encouraging to discover a wider initiative than I’d ever imagined.

Enthusiastic emails and phone calls come in from Rochelle Gandour of North America’s Trout Unlimited, Andrew Graham-Stewart of RAFTS in Scotland, and theWye & Usk Foundation on the Welsh borders. And that’s without counting all the other individual projects that the Wandle Trust has seeded round the south of England and the Midlands over the last few years.

What’s more, it’s not just private enterprise that’s now getting in on the act. TheEnvironment Agency seems to have recognised both the educational and ecological advantages of rearing trout in classrooms and rivers rather than fish-farm raceways – and they’re even running projects like this using deep-substrate Vibert boxes in several rivers in the Cotswolds.

Vibert boxes… I think that’s another whole subject there, don’t you?

26 January

I know they’re negatively phototropic – according to Gideon, too much UV can actually harm them – but half the point of having this tank full of trout in my dining room is studying its little inhabitants up close, personal, and with a camera. So I take a calculated risk, and rig up a makeshift studio for some digital photos.

Propping up a lightweight table lamp on top of the tank, poised to throw a saucer of light straight down onto the quietly-fluttering shoal, I crouch in front of the glass to line up my shot. When I think it’s right, I throw the switch on the lamp.

The trout freeze: I click, then kill the stressful spotlight immediately. 3 or 4 more sequences, and I guess I’ve got enough film in the can. Trouty trauma: that’ll do for the day.

27 January

What did I say last month about insights into fly tying? Watching the trout in their tank this evening, I think I’ve hit on another one.

With those big dark eyes, diaphanous outline, and single scarlet vein, there’s nothing these alevins resemble quite so much as a Winter Brown spider fly pattern - about size 14, with a slim red thread body, soft woodcock hackle, and just-outsized peacock-herl head. Supposedly it’s a stonefly nymph, but even its biggest fans admit it’s nothing like any stonefly that flaps or swims. As an alevin, on the other hand, it should look absolutely right for fishing in March, early in the old northern English season… and all the more if freezing water temperatures have kept hatching late and fry swim-up slow.

Every fisherman knows there’s very little that’s new under the fly-tying sun, and if I think about it hard I can even convince myself that I’ve read about this particular hatch-match somewhere before. If so, it’s deeply hidden for now in some forgotten undercut, far from the easily-legible surface currents of my library. Either way, I’m just delighted to have rediscovered one of those wise old spidermen’s insights from my own tank-side vigil.

1 February

Looking in on the alevins today, I tell myself for a moment they’ve disappeared. Then I see the shifting shadow behind the vertical aerator tube: every troutlet well away from their original redd, fleeing from every source of light, huddling in the safest, darkest corner of the tank.

Intelligent mobility… but that’s not the only sign of growing up. Even now they’re larger and distinctly darker than they were just a couple of days ago, all that striking haemoglobin-red completely replaced by a blacker bloodvein, the kidney that lies along the backbone of an adult fish.

In the shape-shifting vise of my imagination, the spider patterns are turning into streamers already…

10 February

Sadly, it’s turkey baster time again. 3 alevins are lying out on the gravel in strange contorted postures, their colours pale and fading. One is twitching slightly, the other two are clearly dead, with spines twisted, outlines already furred with fungus, and yolk-sacs noticeably less-absorbed than those of their healthier brothers and sisters.

Even this small loss feels like a failure – but I know from our schools’ frequent extinction events in past years that there’s probably far worse to come.

And after all, 200-odd still surviving out of maybe 220 eggs is an exponentially better rate than they’d be achieving in the wild.

18 February

Gideon calls this evening to see how the Carshalton hatchery is faring. At first he’s surprised to hear there’s no sign of swim-up yet, but we agree that’s because I’m still keeping them in the dark, holding them back, making sure all their yolk-sacs are properly absorbed before I turn up the heat and push them towards their topwater lifestage. Whereas the kids want to be able to watch them all day in their school hallways and science labs…

By the end of our conversation, in fact, we’ve decided to keep the tank at an experimental 10 degrees, and see how they’ll behave of their own accord. After all, the Wandle wouldn’t gain 2 degrees overnight at this time of year – and in this case there’s far less need to force developments than in a school where we’re growing trout to involve and engage a new generation of humans before the looming deadline of Easter hols…

But no matter how much I do hold them back, it’s still only a matter of weeks before these babies will have to be taking their chances in the waters of the Wandle – if they’re to develop enough wild-fish behaviours to supplement their instincts and keep them safe for the next 5 to 8 years. Time to start fine-tuning some transitional habitat for them, I think, in the wheel-pool over the road!

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