Aquaculture for all

Lobster Found To Have Shell Disease


NORWAY - A sick lobster handed in to The Institute of Marine Research last autumn has been found to be suffering from epizootic shell disease, which is likely to have been introduced by American lobsters to the native population.

In late autumn last year, The Institute of Marine Research received four lobsters with varying degrees of shell damage. Two of the lobsters had been caught in Viksfjorden, in Larvik Municipality. The two others had spent 4-5 years in aquariums in Ålesund and Drøbak respectively.

Scientists suspected that the lobsters might be suffering from a shell disease that had not previously been found in lobsters in Norwegian waters. The disease causes the lobster shell to rot away, and in the most serious cases it is fatal.

Outbreaks of shell disease have effectively stopped lobster fishing in several parts of the US, where the disease has spread rapidly over the past decade.

"The tests that we have carried out so far suggest that we are dealing with epizootic shell disease. This is based on bacteriological and histological tests, and the visible signs of the disease on the shell,” explains Nina Sandlund, from IMR.

Ms Sandlund emphasises that further specimens must be examined before we can reach any definite conclusion about the disease and the situation in Norway. At least 150 lobsters are needed to give scientists an indication of whether the disease is widespread amongst the American lobsters that live along the coast of southern Norway. It will also be very interesting to find out whether the disease exists in European lobsters.

The Directorate of Fisheries has given permission for controlled experimental fishing to remove any other American lobsters and hybrids from the Larvik area. Local fishermen will catch the lobsters. All lobsters that are caught will be DNA-tested and examined for signs of disease. Lobsters identified as being American, hybrids or diseased will be removed. The remainder will be tagged and put back where they belong.

“But even if we don’t find any European lobsters with the disease, we can’t be sure that the disease isn’t contagious,” emphasises Ms Sandlund.

The disease takes time to develop, so it will be some time before the results of the experimental fishing are known.

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