The Killarney shad[2][3] (Alosa killarnensis), also called the goureen, is a freshwater fish in the family Alosidae, endemic to a single lake in Ireland, Lough Leane in County Kerry.

Research has shown that it is a landlocked subspecies of the anadromous, twait shad (Alosa fallax), arriving in the lake after the Last Glacial Maximum about 10,000 years ago.

[4] The adopted method for conservation involves the identification of spawning sites and protecting them from declining water quality.

[3] DNA-studies confirm that the population is derived from the twaite shad and suggest it arrived in the lake after the Last Glacial Maximum when the ice sheet retreated from Ireland.

The landlocked population has evolved many morphological and ecological peculiarities in the short post-glacial time, and therefore it has been suggested to represent an independent young species.