SOME waterways have undergone a significant ecological change which is taking a heavy toll on trout populations, according to early indications from the most extensive survey undertaken of fish stocks on the west's main lakes.
The findings of the Western Regional Fisheries Board (WRFB) survey, notably in relation to Lough Corrib - the largest of the lakes - are causing grave concern to angling interests.
Pike populations were found to be almost on a par with trout, on what is supposed to be one of Ireland's main game fishing lakes and a key location for angling tourism.
Provisional figures collated earlier this month - at selected sites in the lake - show that 463 pike were found on the Corrib in comparison to 476 trout. Pike arc, however, understood to be particularly active at this time of year.
The board selected over 200 sites randomly spread throughout the lake where gill nets were put down to find out how many fish were present.
Further tests are being carried out by the Central Fisheries Board (CFB) to evaluate diet, particularly of the pike, and genetic characteristics.
Commenting on the Corrib figures, Dr Paddy Gargan of the CFB said they would like to have seen more trout. "The lake would be able to carry a higher trout stock."
The ratio of pike to trout on the Corrib was "disappointing", he said, with average pike caught being 2.58 kilos (over 6 lbs), which is considerable.
Both the pike numbers and their average weight are "worrying" to game fishermen.
Some anglers suggest that the pike are feeding off the more than off any other species.
The reasons for the decline of trout have been the subject of intense debate. It is among the more sensitive species when there is discharge of pollutants, including agricultural and domestic wastes, into a system. "There are indications of a decline in water", quality in many of the region's, waterways, which could be the main contributing factor.
WRFB assistant fisheries inspector, Mr Pat Day, who manages Lough Corrib and was involved in conducting the survey, estimated that there has been a drop off in trout of up to 80 per cent in spawning rivers feeding into the Corrib over the past 15 years.
"The days of catching double figures when out in a boat are over. You are lucky now if it is one or two. You could not say that we are happy with that."
The survey is being conducted on the Corrib system which includes Loughs Corrib, Mask, and Carra. It is a prelude to a £3 million development programme on the lakes which has been approved for EU funding.
Carra/Mask Angling Federation spokesman, Mr Tony Waldron, said the Corrib figures were "disturbing because of the size and number of pike and the collapse in the perch population".
Early indications were of a better trout/pike ratio on the Mask, though the Corrib situation could have implications for the whole system.