Anja Murray: Shameful that our activities have put our waterways in jeopardy for so long

Along with water quality improvements, there is a massive role for active restoration of habitats in rivers and lakes too

Trout: genetic research has revealed there is more genetic variability among trout in Western Europe than there is between the entire population of humans

Waterways across Ireland are home to trout — some lightly speckled, others splodged with big red polka dots. Their colour varies from rich golden brown to light silver and grey. Trout are both the most widespread of Ireland’s indigenous fish and display the most genetic variation of any fish species here. In some cases, fish with the same genes can look different depending on their environment; in other cases, it is gene variants that produce very different-looking fish. In fact, genetic research has revealed that there is more genetic variability among trout in Western Europe than there is between the entire population of humans — a characteristic enabled by the fact that trout have double the number of chromosomes that we humans have.

This also means that trout are an impressively adaptable fish, part of the reason why they were among the first to colonise Irish rivers and lakes, 14,000 to 10,000 years ago, after the end of the last great ice age. Like salmon, they are able to withstand both salty and fresh water, so were able to find their way here across late glacial seas and establish themselves in the numerous post-glacial rivers and lakes that were left in the landscape as the ice thawed and rivers forged their course.