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Demersal fish



Photo: Øystein Paulsen / IMR

The Demersal Fish Research Group (Bunnfisk in Norwegian) studies demersal (bottom dwelling) fish in all our marine areas, with the objective of maintaining and developing the IMR’s principal fields of competence for these fish.

This competence includes the collection of biological data, including length, weight and maturation; data on stock sizes, distribution and migration based on acoustic methods and bottom-trawling.

Areas of scientific responsibility:

Our important tasks are assessment of stock condition; single- and multi-species modelling of stock development; and the provision of management advice.

The daily work is mainly organised into three groupings of co-workers, but there are clear overlap between the tasks:

  1. Stock assessment for the Barents Sea, the North Sea and along the Norwegian coast, including cruise participation. 
  2. Processing biological samples, e.g. diet analysis or obtaining age and other data from otholiths / "ear stones”. Our newly built otolith lab is available for use by other research groups as well.


The Demersal Fish Research Group comprises of approximately 35 people. One member of the group is based in Oslo, while the other members are based at Nordnes in Bergen. The group also includes postdocs, PhD students and master students.


The group is particularly involved in several of the main resource management cruises, as project leaders, cruise coordinators, cruise leaders and research technicians.

Stock assessment:

Our scientists participate in stock assessments in ICES working groups for the following stocks: cod, haddock in the Barents Sea, coastal cod north of 62oN, and saithe north and south of 62oN, but also the demersal fish species cod, haddock, whiting and plaice in the North Sea in addition to saithe. 

Furthermore, we contribute with stock assessment for redfish, halibut and capelin in the Barents Sea, where the responsibility lies respectively at the research groups “Deepwater and cartilaginous fish” and “Pelagic fish”. 

Regarding capelin, cod and haddock in the Barents Sea, multi-species modelling based on diet-analysis from cod are used in the stock models. Read more about the various species in the fact box to the right.

Age determination:

The technicians are specialized in reading the age of various species that we are required to assess. Approximately 70.000 otoliths are being read annually within the group, the majority of these are cod otoliths. Age is determined by counting the number of annual rings in the ear stone, in the same way as one reads annual rings in a tree. See separate theme page about otoliths/ear stones. 

Otolith for a 10-year-old saithe
Otolith from a 10-year-old saithe with three spawning zones (marked in green).
Hvor finner vi otolitten
The location of the otolith in the head of the fish. The age is determined by counting the number of zones, the size of the zone can reflect the growth conditions the fish had a given year.