Ocean quahog

Scientific: Arctica islandica. English: Ocean quahog, Icelandic cyprine, black clam, black quahog. Icelandic: Kúfiskur, kúskel. For more languages see the Marine Animal Dictionary.

Biology and distribution

The ocean quahog is large bivalve that can reach a height of up to 10 cm. It grows rather rapidly during the first years, but the growth slows down after it reaches sexual maturity at the age of about 20 years, at the size of 6 to 7 cm. The ocean quahog can live to a very old age; the oldest individual measured in Icelandic waters was estimated to be about 400 years old. This makes the ocean quahog the longest lived animal on earth. The ocean quahog lives buried in the sediment so only a small opening of the shell is visible. It feeds by filtering phytoplankton and organic material from the sea,

The ocean quahog is found all around Iceland on sand or mud bottom at depths of 5 to 50 m. It also occurs deeper. Where conditions are favourable, the density can reach up to 88 shells per m², or 8 kg. The total stock size estimated in Icelandic waters is more than 1 million tonnes. The ocean quahog has a wide global distribution. It is found in European waters from the White Sea in the north to the Strait of Gibraltar in the south. It is also around the Faroe Islands, and from Labrador to Virginia in North America.

Catch and fishing methods

The fishery for ocean quahog is very specialized. Currently commercial fisheries in Icelandic waters are only conducted by one boat, specially designed to use a hydraulic dredge. Historically the ocean quahog has also been fished with smaller dredges for bait in the cod fisheries.

Stock status (from the Marine Research institute)

In 2009, the fishery for ocean quahog (Arctica islandica) with a hydraulic dredge stopped, and since then a dry dredge has been used. In 2010 only 1 t of ocean quahog was landed, compared to the maximum of 14 400 t in 2003. Since 1987, a fishery for human consumption has been developing, but annual landings have been variable for market reasons. MRI recommends a harvesting policy of 2.5% of the estimated stock size, corresponding to no more than 31 500 t for the quota year 2011/2012.

Processing and markets

The ocean quahog catch is frozen and exported to USA where it is mostly processed into clam chowder soup. A small local market also exists for ocean quahog as bait.

References and further information

References: (Gunnarsson et al., 1998), (Ragnarsson & Þórarinsdottir, 2002), (Schone et al., 2005), (Þórarinsdottir & Jacobson, 2005).

For full citation and further information on the main species in general see this page

Hreiðar Þór Valtýsson, University of Akureyri