Disease in the Jersey ormer stocks (FOI)

​Request

I am writing about ormers.

A

Can you please remind me when it was that a disease last infected our Jersey ormer stocks?

B

What was the disease?

C

How soon did stocks recover?

D

Will it recur?

Response

A to D

The Vibrio Carchariae (‘Wither Foot’) virus was first detected in the local ormer population in 1999 resulting in estimated stock losses of 70 to 90% in Jersey waters and 60 to 80% in north Brittany. As far as we are aware the last local trace of the virus was in 2000.

A ban on ormer fishing in Jersey waters was enacted in 1999 and lifted in 2002. Inspection data collected before and after the ban suggests that the ormer stock was badly impacted and it is suspected that even now there are some intertidal areas where recolonisation has not occurred.

It appears that the 1999 Vibrio pandemic in the Normano-Breton Gulf started at least two years earlier in the Gulf of Morbihan. Laboratory work suggests that mortality onset is linked to sea temperature with the trigger point being circa 17°C. In an average year this would apply to Jersey waters between July and September; however, rock pool temperatures will often reach over 25°C during low water possibly making these environments more susceptible.

We do not know whether the virus will recur, however, it is certainly possible since it has been estimated that only around 15% of stock has a natural immunity.

Recent research of intertidal ormers on Jersey has tracked the movement and growth of individual animals across several years with no current sign of mass mortality and the biggest loss of stock for intertidal populations seems to be due to fishing which is what one would expect from a regularly targeted species such as this. Subtidal populations will be different as they cannot legally be collected through diving.

Please bear in mind that there is still much we don’t know about both the Vibrio outbreak and its legacy on local stocks; much of the above biological information is from research undertaken by IFREMER in the wake of the 1999 event.