The Killarney shad (''Alosa killarnensis''), also called the goureen, is a

freshwater fish Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments differ from marine conditions in many ways, especially the difference in levels of s ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Clupeidae Clupeidae is a family of ray-finned fishes, comprising, for instance, the herrings, shads, sardines, hilsa, and menhadens. The clupeoids include many of the most important food fishes in the world, and are also commonly caught for production of ...

'',

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to a single lake in

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

Lough Leane Lough Leane (; ) is the largest of the three lakes of Killarney, in County Kerry. The River Laune flows from the lake into the Dingle Bay to the northwest. Etymology and history The lake's name means "lake of learning" probably in reference to ...

County Kerry County Kerry ( gle, Contae Chiarraí) is a county in Ireland. It is located in the South-West Region and forms part of the province of Munster. It is named after the Ciarraige who lived in part of the present county. The population of the co ...

. Research has shown that it is a landlocked subspecies of the

anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...

twait shad The twait shad or twaite shad (''Alosa fallax'') is a species of fish in the family Clupeidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea and is an anadromous fish which lives in the sea but migrates into fresh water to s ...

(''Alosa fallax''), arriving in the lake after the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

about 10,000 years ago. This fish is at risk from

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

and the introduction of alien species of fish to the lake and the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has rated it as " critically endangered".

Distribution and status

in the

Killarney National Park Killarney National Park ( ga, Páirc Náisiúnta Chill Airne), near the town of Killarney, County Kerry, was the first national park in Ireland, created when the Muckross Estate was donated to the Irish Free State in 1932. The park has since ...

, southwestern Ireland, is only the place where this fish lives. It has been listed as critically endangered by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

. Eutrophication and introduction of alien fish species such as common roach ''Rutilus rutilus'' and

common bream The common bream, freshwater bream, bream, bronze bream, carp bream or sweaty bream (''Abramis brama''), is a European species of freshwater fish in the family Cyprinidae. It is now considered to be the only species in the genus ''Abramis''. ...

''Abramis brama'' are the most probable threats. The shad is also very sensitive to pollution. The adopted method for conservation involves the identification of spawning sites and protecting them from declining water quality.

Biology

The Killarney shad feeds in the pelagic zone of the lake and spawns in shallow bays. It has a life span of about five years. Males are smaller than the females. They generally feed on zooplankton, and spawn in June - July on gravel bars and gravelled shallows and around the islands of the lake.

Systematics and population history

Most often the Killarney shad has been considered a landlocked

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of the anadromous, widespread

twaite shad The twait shad or twaite shad (''Alosa fallax'') is a species of fish in the family Clupeidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea and is an anadromous fish which lives in the sea but migrates into fresh water to s ...

(''Alosa fallax''), with the name ''Alosa fallax killarnensis''. DNA-studies confirm that the population is derived from the twaite shad and suggest it arrived in the lake after the

when the ice sheet retreated from Ireland. Moreover, there would have been another invasion wave of twaite shad to the lake, also > 10 000 yr ago, which mixed with the first one. 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. The Killarney shad is smaller than the twaite shad (only 20 cm), and has a low

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the ...

number. While the Killarney shad is the only landlocked derivative of the twaite shad in NW Europe, several landlocked populations occur in Southern Europe, but they are not always taxonomically separated from ''Alosa fallax''.

References

* ''Handbook of European Freshwater Fishes'' Kottelat, M. and Freyhof, J. 2007 {{Taxonbar, from=Q142090 Alosa Endemic freshwater fish of Ireland Killarney Critically endangered fish Critically endangered biota of Europe Fish described in 1916 Taxa named by Charles Tate Regan