The Killarney shad is endemic to Ireland, which means that it is a native species that is found only in Ireland, making it a very special part of our natural heritage. Killarney shad are only found in one location, Lough Leane in County Kerry, where it is known locally as "goureen". The Killarney shad is a landlocked, non-migratory subspecies of the twaite shad (Alosa fallax) that probably colonised Lough Leane thousands of years ago and became isolated there. Similar shad subspecies have also been recorded in southern Europe, including Italy and Greece.
Like other shad, Killarney shad are deep bodied and herring-like in appearance, with a sharp keel on their belly, radiating lines on the gill covers and a distinct notch in the upper jaw. Killarney shad are similar in appearance to twaite shad but generally smaller in size.
Killarney shad feed on plankton in the lake, and they are thought to spawn in gravelly areas along the lakeshore and islands. The Killarney shad is a protected species in Ireland, and populations in Lough Leane are considered abundant and robust but nonetheless vulnerable due to its extremely limited distribution.