Long rough dab

Long Rough Dab Illustration: Jón Baldur Hlíðberg

Long rough dab fishing grounds in 2008 (t/nm2), all gear combined, dark areas indicate hihghest catches. Source: The Marine Research Institute Long rough dab catch (t) in Icelandic waters Source: ICES, Statistics Iceland Long rough dab catch (t) by month Source: Statistics Iceland, weigh reports Long rough dab catch per unit effort (CPUE kg per set) from Danish seiners and indices of fishable stock abundance on the southern grounds in the groundfish survey Source: The Marine Research Institute Long rough dab catch (t) by type of processing Source: Statistics Iceland, processing reports

Scientific: Hippoglossoides platessoides. English: Long rough dab, American plaice. Icelandic: Skrápflúra, skrápur. For more languages see the Marine Animal Dictionary.

Biology and distribution

The long rough dab in European waters, can reach up to 60 cm, but the usual size is between 15 and 30 cm for males, and between 20 and 40 cm for females. The growth rate is slow, but females grow faster and become much older and larger than the males, up to 19 years old. Half of the males reach sexual maturity by age 3, but females at age of 4 or 5. The long rough dab spawns all around the country in March to June. It has a broad feeding range and when small, eats various benthic invertebrates. However, as it grows other fish species such as capelin become an important source of food.

The long rough dab is one of the most widely distributed and possibly the most plentiful of Icelandic groundfish. It is abundant all around Iceland at a depth range from 10 to 400 m, usually on mud bottoms but also on other bottom types. The distribution is even, but there are a few places where large individuals are found in aggregations and this is where most of the catches are. There is no information on any large scale spawning/feeding migrations, except that this species goes deeper in the winter. It is abundant on both sides of the northern North Atlantic, from the Barents Sea to the English Channel in the east and from Greenland to Cape Cod in the west.

Catch and fishing gear

The long rough dab does not really have any history of landings in Icelandic waters until after 1986. Only a few tonnes were reported earlier this century by Belgian and German trawlers. Because of its wide distribution but very low value the long rough dab was almost certainly discarded in considerable quantities since trawlers started to operate. But since 1986, catches did increase rapidly to about 6,500 tonnes in 1996. Firstly, because the long rough dab was now retained instead of being discarded and, secondly, because of direct targeting by boats that had finished their quota for more valuable species. However, catches have declined again to low levels due to a decline of the stock.

Usually more than 90% of catches have been by Danish seines. Most of the catches comprise large females, in late winter and spring. This is because the long rough dab is aggregating in spawning grounds at that time.

Stock status (from the Marine Research institute)

In 2009, 290 t of long rough dab (Hippoglossoides platessoides) were landed compared to the record high of 6.400 t in 1996. CPUE is at an historical low and survey indices have decreased in recent years. The MRI recommends the TAC for the quota year 2010/2011 should not exceed what is expected to be landed a by-catch in other fisheries. Considering the state of the stock, this could amount to around 200 t for the 2010/2011 quota year.

References and further information

References: (Jónsson & Pálsson, 2006), (Pálsson, 1997).

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

Hreiðar Þór Valtýsson, University of Akureyri