The quagga is a great threat to Mayo's lakes
COUNTRY FILE
Forewarned is fore-armed, so they say. It is only a few years since the zebra mussel arrived in our western lakes.
Remember how many anglers welcomed that? It is likely the spread of that particular shellfish was encouraged and even facilitated by some who were fed up with seeing once crystal-clear lakes thick with algae.
The algae problem was caused by excessive nutrient run-off.
Nitrogen and phosphate fertilisers washed from fields and into the lakes during rainfall events; the algae grew and water quality suffered.
The zebra mussel was seen by some as a quick fix. Yes, it filtered the water and flourished on the abundance of microscopic food it found.
Vast areas of Mask, Conn, Cullen and many other water bodies are now thickly carpeted with this invasive creature to the detriment of native species.
What have been the results?
Previously turgid water has been scrubbed clean. Sunlight reaches deep through the water column to nourish water plants.
And all that nitrogen, together with other substances that encourage plant growth, has been deposited on the lake bed to feed the banks of weed, which have grown lush and thick.
When I visited Conn with a friend last summer we found entire bays unfishable. The fishing was poor enough anyway.
After two largely fruitless visits we went elsewhere, and although it pains me to say it, I don't know that I shall bother visiting next year.
The trout and salmon, which depend on high water quality, appear to be diminishing in number, while less sensitive coarse fish like roach and bream are increasing exponentially.
Yes, we could eat roach if we wanted, and I guess if things got really tough we could even eat bream, but neither of these fishes is in any way comparable to a tasty Lough Conn brown trout.
But enough of that for now, for something worse than the zebra mussel is about to invade our world famous trout lakes.
Enter the quagga.
While similar in appearance to the zebra mussel, the quagga can grow several times larger. It feeds in the same way, drawing water in through a siphon, absorbing the nutrients it requires and ejecting any other particulate matter onto the lake bed.
Filtered water is returned to the lake though the other end of the siphon.
One quagga can efficiently filter one litre of water a day and one square meter of rock can accommodate many hundreds of these creatures.
A single female quagga can release up to a million eggs in a single season.
These hatch into microscopic, free-floating larvae, which will settle on any suitable surface they come into contact with. In a very short time quagga can become the dominant species in any of our lakes.
And now they are in Lough Derg and Lough Ree, and quite possibly in many other waters as well.
Make no mistake, the quagga is a threat.
In terms of biodiversity, they strip the water of phytoplankton (microscopic plant life) and in doing so deprive zooplankton (miniature animals essential for good water quality) of their food source.
They accumulate toxins, first in their excrement (called pseudofaeces) and secondly in their own flesh, so that anything eating the quagga is liable to poisoning of one kind or another.