We have some indications within the Historical Malacological Collection of Pietro Parenzan. However we haven't any GPS position because of our data are of about 50 years ago.

I have reported the presence of C. gigas in northern Sardinia in this work: https://www.researchgate.net/publication/250003848_Molluschi_alloctoni_rinvenuti_lungo_le_coste_del_comune_di_Olbia_%28Sardegna_nord-orientale%29_rassegna_dei_dati_disponibili?

You can also find literature on the distribution of this species in europe in this article:

v = prf_pubhttp: //www.imr.no/genimpact/filarkiv/2007/07/pacific_cupped_oyster.pdf/en

Article Molluschi alloctoni rinvenuti lungo le coste del comune di O...

Thank you both for the information. Mauro, did you record the GPS position of C. gigas in Sardinia for your publication? I also had a look at the reference you suggested, but there is only a distribution map in the publication. Such distribution maps are very common, but it's often very hard to find the data they are based on. It's often "common knowledge" or records of existing fisheries which is the base for such maps, not actual observations. If anyone disagrees, please feel free to correct me :)

Dear Asa,

did you check the following databases:

- WoRMS - World Register of marine Species: http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656   (see publications as references for the distribution records).

- EMODnet: http://www.emodnet-biology.eu/portal/

(and others available through the data portal: www.eurobis.org/data_access_services)

Dear Nancy. I have had a look at Worms, but often the references doesn't report GPS positions, making the data hard to use. The EMODnet however is a gem! Thank you so much for the advice. Lots of records available for France :)

Dear Åsa, I have not recorded GPS data for my publication, but I know that the coordinates are 40.810177, 9.672363 (San Teodoro coastal pond)

Mauro

Tanks Mauro!

Dear Asa, did you check the following databases?

http://www.europe-aliens.org/speciesFactsheet.do?speciesId=50156#

http://www.nobanis.org/files/factsheets/Crassostrea%20gigas.pdf

http://easin.jrc.ec.europa.eu/use-easin/species-search/species-search-by-name

Dear Åsa

Just in case you did not know: there is also the closely-related alien oyster Crassostrea angulata. European records are probably relatively southern ones. The species is probably often treated synonymous with C. gigas. More on that in WoRMS under taxonomy. WoRMS considers these as separate species.

http://www.marinespecies.org/aphia.php?p=taxdetails&id=146900

Dear Ainhize, thank you for your suggestions! The distribution maps are really nice, however, I need the GPS position for observations of the species which often is not presented in the distribution maps. I will contact the administrator for the EASIN database to see if I can get access to the positions underlying the map they present.

Dear Godried. Thank you for your reply. Yes, I am aware of the discussion about the two oyster species (or not....?). The species concept is not always straight forward. My first objective is to find presence records of C. gigas, the second step is to validate the observations is actually of C. gigas and not of C. angulata. I know this might not be very easy, but I have to start somewhere. Perhaps in the end I just have to travel along the south European coast and make observations of my own, that wouldn't be too bad :)

you can consult this site where you find a map of the species in the Mediterranean:

http://www.marinealien.sinanet.isprambiente.it/uploads/Crassostrea%20gigas.pdf

a national database has been created with the cooperation of the Ministry of the Environment, where also coordinates have been collected

Hi Luca and thank you for the information. You don't happen to have a link to the database? I couldn't find it at the governmental webpage.

Currently you can only download the sheet of each alien species recorded where also literature of the records has been reported. This atlas is updated to december 2011. 

Ok, thanks Luca

Hi,

not sure if this is relevant for your research, but in the Tejo estuary, near Lisbon, Portugal, there were very extensive oysterbeds until the early 1980s, after which the oyster died off apparently do to industrial polution and its effect on their ability to reproduce. The oysterbeds are still there, and easily visible from aerial imagery, but all oyster are now dead. Although they were always assumed to be all C. angulata, I am not sure if anyone ever confirmed that it was always the case.

From my experience, I can suggest you to investigate the sites in the Adriatic Sea where artificial reefs have been placed. In the period of my fellowship I studied them in northern Adriatic and I found several specimens of C.gigas. I send you two old publications on this matter 

Back in 1993 we had recorded some small specimens on the east coast of Malta in an area affected by a sewage outfall (at the time untreated). There might have been other records since then.

I work in the northern Adriatic Sea, particularly in the northernmost sector. This species was introduced in the Lagoon of Marano and Grado in '80th for aquaculture purposes, but doesn't has any economic interest. Thus it spread naturally all over lagoon, forming oyster banks and causing problems to navigation and to manila clam culture. in order to get any other information on this area you can find on my profile a paper rgarding manila clam harvesting. best regards. Nicola 

Hello Asa,

you are asking for records southwards of northern France, for which I can not help.

But are you aware that C. gigas is also present in The Netherlands (from North to South, harvested) and Belgium ?

Besides, this link offers a world map with the countries where it is 'cultivated'.

Regards. Alex

Better with the link, doesn't it ?

http://www.fao.org/fishery/culturedspecies/Crassostrea_gigas/fr#tcNA0064

Dear all. Thank you for all your replies and I'm sorry for not being so active lately.

Pedro: it's interesting to hear that the oysters actually dissapeared, and that the reef structures are still visible after such long time. Thus even as post-mortem structures the species may have big impact on local ecosystems. Did the oyster manage to disperse to other nearby sites before dying off?

Luca: thank you for the publications!

Adrian: do you know of anyone I can contact regarding observations in Malta since 1993?

Nicola: I have had a look at the paper you suggested (I hope I found the right one), but I couldn't find a reference to the occurrence of C. gigas (I did find a reference to the import of spat for oyster production). Do you happen to know any other papers where the occurrence of the species is reported or know of any actual sites where the species can now be found?

Alex: yes, I'm aware that the species is also present in high densities in Holland and Belgium. We have managed to get records from both countries, so it's mostly southern Europe (from southern France and southwards) that we need more records. Thank you for the remark.

Alex: and for the link :)

Hej Narimane :) Thank you for the links, my french isn't very good, but I have a colleague who can help me to navigate the websites. The researchers at IFREMER are very skilled and posses a lot of knowledge, but they are also very busy (as we all are), so if I can manage to get the information without disturbing them it would be great :)