Feeding of mature cod (Gadus morhua) on the spawning grounds in Lofoten

Many authors state that cod (Gadus morhua) do not feed during the spawning period. However, this more or less established fact has rarely been investigated in the field. Here, the content of stomachs from Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC) sampled from the spawning ground in Lofoten were examined over a 10-year period (1996–2006). The occurrence of food in the stomachs of spawning cod, stomach fullness, diet composition, and variation in these variables between NEAC and NCC, year, and sex were analysed and compared. The analysis shows that cod do feed, even when they are in a spawning state. NCC had a lower proportion of empty stomachs and the stomachs were fuller than those from NEAC. Females had a lower proportion of empty stomachs than males and their stomachs were in general fuller. Herring (Clupea harengus) dominated the diet of cod. However, cod consumption of herring on the spawning grounds seems to be a minor source of mortality on herring. Although spawning cod do feed, the proportion of empty stomachs was higher and stomach fullness was lower than in stomachs of NEAC from the Barents Sea

The role of cod in the decline in arctic fishes in the Barents sea

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Spatial variation and structural change of the Barents Sea fish community

We document the spatial patterns found in the Barents Sea fish community in relation to environmental parameters, analysing data from the ecosystem surveys covering the Norwegian part of the Barents Sea during 2004-2008 and comparing with earlier investigations of the deeper areas from the period 1992-2004. Changes in the ecosystem, expected on the basis of changing climate and harvest regimes may often go undetected due to strong focus on oceanography and commercial species of monitoring programs. Fish species that are not targeted by fishery are included in the analyses, providing valuable, additional ecological information on structural alterations. We identified species assemblages associated with different water masses and range of productivity of sea areas. Major changes in the structure of the fish community occur in this previously thought healthy, resilient and well-managed large marine ecosystem. The spatio-temporal analyses of the Barents Sea survey data from this decade shows that a new fish community structure is in place compared to the general community structure of the previous decades. An ecological regime shift in the 90-]ies might be speculated. The change is concurrent with a climatic regime shift and may be persistent

Survey report from the CODFUN 2016114 Barents Sea survey 5.-11. oktober 2016

The survey is part of the project “The cod – capelin interaction in the Barents Sea: spatial dynamics in predator prey overlap and functional response (CODFUN)” funded by the Norwegian Research Council (NRC project number 243676/E40). The CODFUN project was motivated by the need to update and improve the current formulation of the functional response of cod used in the capelin assessment model. The functional response is the relationship between the feeding rate of individual predators and density of prey. Functional response, together with density of predators and prey is used to calculate natural mortality. In all natural environments, there is spatial heterogeneity in densities of prey and predators and their overlap. This heterogeneity becomes a very important determinant of natural mortality due to predation. The aim of the CODFUN project is to quantify and explain spatial heterogeneity in the capelin-cod interaction at different spatial scales in the Barents Sea. The aim of the survey was to study spatial variation at the scale of individual cod and capelin schools. We aimed at quantifying attack rates of cod on capelin using acoustics, and to estimate proportion of successful attacks using stomach samples from trawl catches and handline. Furthermore, we aimed to relate variation in attack rates to variation in capelin densities and light conditionspublishedVersio

Year-to-year dynamics of trophic links of the main commercial fishes in the Barents Sea as indicating the state of ecosystem

Ecosystem dynamics and optimal long-term harvest in the Barents Sea fisheries. Proceedings of the 11th Russian-Norwegian Symposium. Murmansk, 15-17 August 2005

Investigations on demersal fish in the Barents Sea winter 2006

A combined acoustic and bottom trawl survey to obtain indices of abundance and estimates of length and weight at age has been carried out each winter (4-6 weeks in January- March) since 1981 in the Barents Sea. The target species are cod and haddock, but abundance indices have also been worked out for the redfish species since 1986 and Greenland halibut since 1990. Prior to 1993 a fixed standard area (ABCD in Fig. 2.1) was covered, but in 1993 the survey area was extended to the north and east in order to obtain a more complete coverage of the younger age groups of cod. In winter 1997 only the Norwegian part of the Barents Sea and a small part of the Svalbard area was covered, while in 1998 also a small part of the Russian EEZ was covered. In 1999 and 2000 the Norwegian vessels had full access to the Russian EEZ. In the years 2001-2005 a Russian research vessel covered the areas where the Norwegian vessels did not have access. In 2006 no Russian vessel participated, and an area off the Murman coast could not be covered

Bunnfiskundersøkelser i Barentshavet vinteren 2006

A combined acoustic and bottom trawl survey to obtain indices of abundance and estimates of length and weight at age has been carried out each winter (4-6 weeks in January- March) since 1981 in the Barents Sea. The target species are cod and haddock, but abundance indices have also been worked out for the redfish species since 1986 and Greenland halibut since 1990. Prior to 1993 a fixed standard area (ABCD in Fig. 2.1) was covered, but in 1993 the survey area was extended to the north and east in order to obtain a more complete coverage of the younger age groups of cod. In winter 1997 only the Norwegian part of the Barents Sea and a small part of the Svalbard area was covered, while in 1998 also a small part of the Russian EEZ was covered. In 1999 and 2000 the Norwegian vessels had full access to the Russian EEZ. In the years 2001-2005 a Russian research vessel covered the areas where the Norwegian vessels did not have access. In 2006 no Russian vessel participated, and an area off the Murman coast could not be covered

Report on the diet of the blue whiting in the Barents Sea in the summer 2005 and in the winters 2002 and 2006

We analyzed stomach content of blue whiting in the Barents Sea in February-March 2002 and 2006, and in August-September 2005. Krill was the most important prey for blue whiting in the Barents Sea, and constituted about 90% of diet in winter and 50% in summer. Blue whiting also fed on amphipods and fish, including blue whiting. Copepods, an important group of prey for blue whiting in the Norwegian Sea, was unimportant in the diet in the Barents Sea. NORSK SAMMENDRAG: Vi undersøkte dietten til kolmule i Barentshavet i februar-mars 2002 og 2006, og i august og september 2005. Krill var det viktigste byttet til kolmula i Barentshavet, og utgjorde ca 90% av diett om vinteren og ca 50% om sommeren. Kolmula spiste også amfipoder og fisk, inkludert kolmule. Hoppekreps som er viktig for kolmula i Norskehavet, utgjorde en ubetydelig andel av dietten