News Irish News

Thursday 23 November 2017

Overheated rivers are killing our endangered crayfish

Our native white-clawed crayfish
Our native white-clawed crayfish

Jerome Reily

TWO major fish kills in Irish waters that also wiped out large numbers of globally endangered white-clawed crayfish are being blamed on rivers and lakes getting too warm, the Sunday Independent has learned.

Unseasonal high temperatures, combined with compromised water quality and low levels after a dry spell sucked the oxygen out of a river in Longford and a Leitrim lake.

More than 2,000 fish – including brown trout, roach, pike, eel and white-clawed crayfish – were among the species found dead on a 6km stretch of the Camolin River, a Shannon tributary, downstream from Longford town.

Inland Fisheries Ireland (IFI) officers are also investigating an incident of fish mortalities at Lough Keeldra outside Mohill in Co Leitrim.

The incident was reported to IFI on September 10. Considerable numbers of dead perch were recorded at the lake site. Live fish observed in the lake were in distress.

Blue/green algae has recently bloomed in the lake. As Lough Keeldra is a designated bathing area, Leitrim Co Council has banned swimming until the cause of the fish kill is fully identified.

"After a prolonged period of low flow levels and unseasonably high water temperatures, all aquatic life but especially fish are extremely vulnerable to the slightest deterioration in water quality," a spokeswoman told the Sunday Independent.

The loss of white-clawed crayfish was a particular blow. Ireland is a world sanctuary for the freshwater crustacean that resembles a small, three-inch lobster.

Elsewhere is Europe, including England and Wales, the species are being wiped out by the invasive American signal crayfish – originally imported to be farmed.

Not only does the aggressive signal crayfish devour our small native species, but it also carries a virulent infection called crayfish plague. The signal crayfish is immune to the fungal infection, but the plague kills white-clawed crayfish within weeks.

Julian D Reynolds of Trinity College is a worldwide expert on the white-clawed crayfish. He told the Sunday Independent: "We are the only country in Europe which does not have signal crayfish, which means our population of white-clawed crayfish is globally important.

"There's a big problem with these species being brought in elsewhere and we have to be so vigilant, especially since there may be a route into the country from Northern Irish waters.

"In the UK the signal crayfish is making inroads into the salmon and trout fisheries, and it's polishing them off," he said.

Meanwhile, Junior Minister Fergus O'Dowd has revealed that fisheries inspectors are being equipped with a range of high-tech gadgets to tackle poachers and polluters. They include night-vision scopes, thermal imaging equipment and covert cameras.

Inspectors use jet skis and quad bikes to catch bass poachers, while kayaks are used to silently patrol rivers.

"Some of the best successes have come from the use of covert cameras," said Mr O'Dowd. "These cameras are covertly located overlooking a known poaching hotspot. The advantage is that they can use infrared light and operate in pitch darkness and they take an image of the subject and text it to the Fisheries Office," said Mr O'Dowd.

Inland Fisheries has also recently had its first operational success with its pilot dog patrol unit. Its dog, Sitka, is able to sniff out nets and stored fish. In 2012 IFI seized nearly 25km of illegal net.

Sunday Independent

Promoted Links

Today's news headlines, directly to your inbox every morning.

Promoted Links

Editor's Choice

Also in Irish News