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Is the spread of the Crayfish plague inevitable?

Outdoor Living

ENDANGERED SPECIES? Crayfish plague is highly contagious and would cause 100 percent mortality in our native crays.

Freshwater crustaceans will almost certainly disappear if outbreak happens

Country Sights and Sounds
John Shelley

My otter quest continues. Despite being hard on the heels of my target he or she continues to elude me. At this point in time any old otter will do. With this thought in mind tracks and well used trails, together with other indications, led me along a derelict tributary where nobody else had walked for years. This small stream once fed a mill – the remains of it still stand – and was doubtless an important thread in the social fabric of the area, with children splashing in the shallows, mothers and fathers drawing water and old men leaning at the sun-warmed stone arch that spans the flow to talk about their youth.
It was valuable for the wild things that live around as well.
Waterways are highways for wildlife. Even now my otter shares his path with the fox, which leaves distinctive, four-toed impressions in soft ground, and judging by the nibbled bark at the base of trees occasionally with a hare or two. On the rounded top of a large rock I found more crayfish shells, including one that must have housed the granddaddy of all white-clawed crays.
Ireland is home to an internationally important population of these creatures, which do especially well in the rich limestone rivers and lakes of the mid west. They are, however, imperilled. Crayfish plague continues to spread across the country with the latest outbreak only a short distance away, on the River Clare which flows into Lough Corrib.
Crayfish plague is highly contagious and causes 100 percent mortality in our native crays. It is spread in two ways. First, it is carried by the North American Signal crayfish. Should these find their way into Irish waters every one of our native crayfish would be eliminated from those same areas. Hopefully we can keep them out, for as the National Parks and Wildlife Service (NPWS) website tells us “if non-native crayfish have been introduced then the disease is likely to become established with severe and probably irreversible ecological impact on Ireland’s freshwater fauna and flora.”
The other means by which this disease is spread is virtually impossible to control. Wet fishing equipment, including boats, engines, boots and clothing and even rod and reels can carry crayfish plague from one water to another. The NPWS have appealed to anglers and all other water users to be vigilant in disinfecting and drying everything that might transmit this pathogen.
Perhaps our angling tourists will follow the lead we set and comply with that request. I doubt it, for the instructions given are not conducive to a peaceful and relaxing fishing holiday.
Anglers, kayakers and others who use Ireland’s waters are asked to check, clean and allow all their equipment to thoroughly dry out and remain dry for a period of 48 hours, and even to power wash or steam wash all their gear at the end of their day. An alternative to this is to chemically disinfect everything before moving from one location to another.
But how will we dry and disinfect my otter? After all, he has a wide range and doesn’t confine himself to any particular area. His territory overlaps with that of other otters, and as crayfish are one of his favourite foods it is inevitable that he or his friends will come into contact with the plague and carry it with them wherever they go.
And what of his co-inhabitants, kingfisher, heron, cormorant, and the ducks, geese and swans that move from one place to another as they will? It seems inevitable that the disease will run its course and we shall move into the Post-crayfish Age as another of our native species bites the dust. Still, that doesn’t mean we needn’t make the effort and do our best.
We might wonder what life would be like if we were to lose the White-clawed crayfish. The answer is simple: for most of us it will make no difference. The world will still turn. For the otter, it will mean the loss of one of his staples. For the trout in the rivers and lakes which feed heavily on these charming invertebrates, it will be the same but worse, for the otter will turn his attention to them. For an upcoming generation it will provide an opportunity to finance yet another faltering reintroduction project.
In terms of biodiversity we have a disaster pending, one that will take a conscientious effort to avert. Once introduced, Crayfish plague kills swiftly. All we can do is to try, and encourage others to do the same.