First published 2013 Invasive: High impact Invasive: Documenting Ireland’s Wildlife Ireland’s Documenting Pacific oyster attached to a rock showing dark cream dark cream showing a rock to attached oyster Pacific purple markings with dark coloured coupled colouring GBNNSS Brazier © Paul

Close up Pacific oyster, notice the white shell surrounding shell surrounding the white notice oyster, Close up Pacific the oyster © Shuttestock

Please report your sightings of this species at: this species of sightings your report Please http://invasives.biodiversityireland.ie

Marine the country. of west the north and to Localised Established. Ostreidae. million in a eggs 50-100 can release The species place takes generally Spawning single spawning. °C. 18-26 between

Cream/off white though it can be very variable, usually with variable, though it can be very white Cream/off a muscle inside with shell is white The frilly oval purple streaks. which is typically purple in colour. scar, and dependent on the habitat and irregular variable Extremely 18cm in length. Can be up to type. and substratum 10 years. up to and can live one year after Matures in cool, days several for water out of can survive The species psu. 11-34 of salinity range a broad have They damp conditions.

Crassostrea gigas Crassostrea Pacific oyster Pacific

Shape: Age: Conditions: Colour: Identifying features Identifying

Habitat: Species profile Species in Ireland: Distribution Status: name: Family Reproduction:

Underside of the shell, the shape of the species can be the shell, the species Underside of the shape of variable very © Shuttestock The National Biodiversity Data Centre Data Biodiversity National The Pacific oyster Invasive: High impact

Threats

Can compete with native species for food and space if it is found in heavy densities.

Uncontrolled harvesting of contaminated oyster can lead to diseases in humans.

The oyster is host to a wide range of pests and parasites and known to carry a number of cryptic diseases.

Similar species Distribution of the Pacific oyster in Ireland, the coloured scale bar indicates the density of records (Biodiveristy Maps) Eurasian flat oyster(Ostera edulis) differs from the invasive Pacific oyster as it has a more rounded shape and a shell without dark coloured streaking.

Pacific oyster showing off white-cream colouring with dark purple streaking The European flat oyster (Ostera edulis) has a more © Paul Brazier GBNNSS rounded shape and different colouring © Jan Johan ter Poorten

View Ireland’s distribution of this species on http://maps.biodiversityireland.ie Biodiversity

National Biodiversity Data Centre fact sheet. Produced with funding from The Heritage Council Maps and the EPA STRIVE Programme 2007-2013 Text: Colette O' Flynn & Oisín Duffy (Version 1) November 2013.