New alien parasite detected in Swedish aquacultures


[2020-11-04] Recently, a group of scientists from the IVL Swedish Environmental Research Institute working with the local Aquaculture company Bohus Seaculture discovered a population of mud blister worms Polydora sp in oysters collected from a natural oyster bed located along the Swedish West coast.

Initial inspection of the specimens indicated that the worms were not any of the native species, but suggested the presence of P. websteri, a well-known invasive alien pest that is a major problem in oyster aquaculture globally. Seanalytics has now applied its standard genetic identification protocols to samples from the oyster bed and we can confirm the identity of the species as Polydora websteri. Together with IVL, we will now collect samples from other oyster beds to better understand the distribution and prevalence of this alien species in Swedish waters and its potential consequences for aquaculture on the Swedish west coast.

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The red circle in the above photograph indicates the black marks typical for P. websteri. Photo credits: Sven Sahlin.