Madam, - The politicians have now banned drift-net fishing but have they "caught" the cause of the decline? In an increasingly populated world it is not just a question of balancing economic advantage with tradition, but more importantly of eliminating causes of losses to the food chain.
Some years ago I investigated trout fish-farm kills on the Upper Bann and it became clear from research by others that aluminium can have a serious impact on trout and salmon. The Canadian guidelines have been that aluminium levels in rivers should be below 0.1 mg/l (half the drinking water limit). Water treatment works use aluminium sulphate to remove colour and other impurities from drinking water and some sewage works have used ferric aluminium sulphate to remove phosphorus. Due care and attention has not always been used in disposing of sludge from these works and in some cases the sludge has been discharged back to the rivers to the detriment of the unfortunate fish. There has also been "carry-over" of aluminium in discharges from sewage treatment works to rivers as a result of using of ferric aluminium sulphate.
Some years ago I sent a copy of my report to the Environmental Protection Agency and since then I note that some monitoring of aluminium in rivers has been done. What is really needed is a "reality check" on what is happening to all aluminium used in water treatment to see that it is being used correctly and to be sure it is not damaging fish in our rivers and spawn laid downstream.
As a child about 1950 I remember seeing the bottom of the Corrib River in Galway covered with salmon waiting to go up the river, and I still have my father's photograph of them. I also remember brackish bog water coming out of taps. Now, when you drink pristine, aluminium-cleaned water, remember: you may be drinking a "toast" to declining salmon and trout stocks. - Yours, etc,
CHARLES B. LAMB, Timoney, Roscrea, Co Tipperary.