independent

Thursday 2 October 2014

Rate of invasion of alien species is increasing

Published 18/02/2014 | 05:34

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Pike: It was long believed that they were aliens introduced here by the Normans.

A NEW report published by the Waterford-based National Biodiversity Data Centre finds that the rate of invasion of alien species to Ireland is increasing.

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As an island nation, all of our species fall into two broad groups: those that got here under their own stream and those that were introduced by people either intentional or accidentally.

Those that got, or get, here under their own stream are regarded as natives. Those that were, or are, introduced by people are aliens. The invasion of alien species to Ireland is on the increase with nearly four times more seen in the wild in the last century than in the previous one.

Some aliens are invasive and threaten our biodiversity, economy and health. The National Biodiversity Data Centre estimate that the annual cost of alien species to Ireland is €261 million. That's an annual bill we could certainly do without. We all can play a role in helping to prevent the introduction of aliens, in reporting sightings of them and in contributing to preventing their spread.

There is a widespread, if somewhat simplistic, perception that natives are good and aliens are bad. Take the Pike for example, a common fish. Pike are hunters, predators of other fishes. Pike are, in fact, the largest predatory freshwater fish we have in Ireland.

And they are perfectly evolved killing machines with a long, torpedo-like body enclosed in a grey-green mottled, spotted and striped camouflage suit and a large head, sharply pointed like a pike. The pike-shaped head is said to be the source of the fish's name. The large head bears prominent eyes and the huge mouth is armed with a fearsome array of sharp, pointed teeth.

Their efficiency as hunters is aided by their habit of skulking and lying in wait among weeds lit by dappled sunlight. However, their efficiency as hunters has not endeared them to fly fishermen who fear their potential negative impact on trout stocks. Where they came from has always been controversial. Though rather bony, they can be eaten and are said to be very tasty. It was long believed that they were aliens introduced here by the Normans.

A recent genetic study on Pike by Debbi Pedreschi has revealed that the species colonised Ireland in two waves; the first wave coming in naturally around 8,000 years ago and the second round 1,000 years ago during Norman times. So the Pike is a native, its population boosted by aliens.

Gorey Guardian

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