Invasive Aliens by Dan Eatherley

Author:Dan Eatherley [Dan Eatherley]
Language: eng
Format: epub
Publisher: HarperCollins Publishers
Published: 2019-05-27T16:00:00+00:00

9

Freshwater Invaders

‘Thence home and to see my Lady Pen, where my wife and I were shown a fine rarity: of fishes kept in a glass of water, that will live so for ever; and finely marked they are, being foreign.’

The Diary of Samuel Pepys, Sunday 28 May 1665

‘If it’s a big one, we’ll put it back in the river.’

‘Fran can castrate it.’

The conversation emanating from the stable-block that morning was jovial. All around were plastic buckets, bin-bags, wooden stakes, wading boots, nets. A fridge-freezer hummed in the corner. The aroma of horse manure and river water hung in the air.

I got speaking to one of the older volunteers, who was stuffing some paraphernalia into a rucksack.

‘What have you got there, Tom?’

‘Callipers to measure. Knives to kill. Scissors to sterilise. First aid kit. Body bag,’ he said. Tom was from Maidenhead but owned a holiday home nearby.

‘Site seven today, Tom, OK?’ said Nicky Green, who was leading operations. Tom nodded.

Just an hour earlier, Nicky had collected me from Tiverton Parkway railway station in a well-used dark-green Mazda Bongo camper-van. Panting and scampering about in the back was a Lurcher, called Twig, who occasionally rested her muzzle on my right shoulder. While we snaked up the wooded Exe Valley to the farm near Withypool in Exmoor that served as her study base, Nicky spoke of the motivations for her research.

‘In Devon, there are only two populations of white-clawed crayfish left, and it’s completely gone from southeast England,’ she said. ‘I was more and more unhappy about the situation and wanted to do something about control.’

In Nicky’s mind, the signal crayfish is to blame. The species, originating in the west coast of North America, gets its name from a whiteish patch atop the rear section of the hefty brick-red claws which were once (erroneously) thought to be brandished, flag-like, at other crayfish. Now widespread across England and Wales since its introduction in 1976 by the Ministry of Agriculture, Fisheries and Food to diversify agriculture, signals pass on a pathogenic water mould, called ‘crayfish plague’, to white-claws, at the same time outcompeting them for food and shelter. (Incidentally, Nicky isn’t too concerned by the debate as to the nativeness or otherwise of white-claws, accepting that the crayfish may have been brought to Britain from the continent during the medieval period. As she recently put it in an email: ‘Yes, it could be introduced, but do we have a responsibility to assist in the protection of a species endangered to Europe?’) Along the way, the signal’s burrowing activity undermines river banks, increasing the risk of flooding. The silt which is released into the water smothers invertebrates and clogs the spawning grounds of salmon and brown trout, whose eggs and fry the signal will also consume.

Formerly an ecological consultant, Nicky had been working off and on with signal crayfish for many years, and was all too aware of the difficulties in eradicating them from Britain’s waterways. Tactics such as the release of chemicals risked harming other wildlife.

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