Niall,
Sorry to bear bad news
As mentioned already it's a hen salmon Kelt. Basically this means it has spawned last winter, and would be on it's route back to sea. They take up this silver apperance after spawning, hence the term 'Well mended Kelt'. Cannot comment on Irish fisgeries law, but it's an offence to kill kelts in Wales, England and Scotland.
Might be an idea to withdraw the pic
If you need any more info please feel free to contact me