UK salmon, trout stock threatened by deadly parasite

Stocks of the UK's Atlantic salmon along with varieties of domestic brown trout could be under threat from a deadly parasite, according to research led Bournemouth University (BU).

Researcher Rodolphe Gozlan believes the disease is a rosette agent or parasite first identified in the UK in 2005.

The agent - sphaerothecum destruens - was originally found in the US and is closely associated with 'invasive' fish species including top-mouth gudgeon and could prove deadly to native salmonids like the atlantic salmon, brown trout.

Gozlan initially found that the parasite poses a severe threat to some freshwater fish species in Europe, but latest findings have serious implications in understanding the potential risk posed by the association in the UK of this disease, the rosette agent, with invasive fish species.

North American isolates of the rosette agent have been shown to cause both high morbidity and mortality in various salmonid species including Atlantic salmon, brown and rainbow trout.

Analysis of the European strain indicates a degree of isolation between European and North American rosette agent populations.

Gozlan said that unlike in the US, the occurrence of the agent in invasive fish presents a major risk of spread from wild invasive populations to sympatric populations of susceptible native fish, noting that a risk for fisheries and commercial aquaculture, as movement of fish for stocking purposes is common practice.

He added that more work is required to determine the extent of the threat to UK and European fish diversity.