January 25, 2007
Recently, I was reading flyfishmagazine and a linked article. I was moved to post a comment back on the blog, questioning the wisdom of genetic manipulation of fish stocks. Then this morning on my way to the office, I read a short piece in Metro, mentioning how Columbus crabs (Planes minutus) had been found in Sennen Cove, Cornwall. They’d floated all the way from Florida!
This started me thinking again, this time about alien species and the vehicles for their introduction. It seems those Columbus crabs arrived through pollution – see for yourself in The Wildlife Trusts reports. On this occasion a piece of polystyrene was the vessel of transportation. The hulls of boats and ships, the holds of transporter planes, the cargo these vessels carry; all transport living organisms to new environments. The Chinese Mitten Crab arrived on the River Thames by these means (in the ballast water of cargo ships). In the name of environmental improvement people introduce foreign species directly into the environment, the Zebra Mussel is a case in point. Farming has introduced alien species, and it has also been indirectly responsible for the introduction of foreign species, either through accidental or assisted escapes: In the UK, mink (Mustela vison), and signal crayfish (Pacifastacus leniusculus) are two examples.
Then we have to look closer to home. Mud snails have been inadvertently introduced by anglers carrying them on their wading boots. Parasites like Myxobolus cerebralis, gill flukes, and eye flukes are likely to have been accidentally introduced through fishery stocking programs. Let’s face it, the vectors for species invasions are numerous and their effects, sometimes positive but frequently devastating. By devastating, I mean they result in the displacement and sometimes virtual extinction of native species; they can cause persistent distress and disease; and perhaps most visibly they can lead to physical environmental damage. Chinese Mitten Crab, Japanese Knotweed, and Himalayan Balsam are three destructive invaders to UK shores.
So what are we to do about all this? Well, I guess exercise caution and conduct ourselves responsibly and thoughtfully. While pollution may be a minor vector for species invasions it’s not hard careful waste disposal and recycling we can reduce pollution. Between trips we can also follow basic biological control by decontaminating our clothes and equipment. In organised groups like conservation organisations, for example Wild Trout Trust, Trout Unlimited, and the ACA, we can undertake physical programmes of work, or lobby government and industry.