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Search: authors:"Harald Gjøsæter"

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Atlantic cod (Gadus morhua) feeding over deep water in the high Arctic

The Atlantic cod (Gadus morhua) is a highly adaptive demersal, boreal species with a broad distribution on the continental shelves on both sides of the North Atlantic. However, whether the species also uses adjoining deeper water basins as feeding grounds or migration corridors remain unknown. In this study, we aimed to describe the vertical and horizontal distributions of Atlantic ...

Predation on early life stages is decisive for year-class strength in the Barents Sea capelin (Mallotus villosus) stock

Year-class strength of Barents Sea capelin has been monitored closely since the early 1970s and during this ∼45 years period three short periods of almost total recruitment failure leading to three stock collapses have been observed. These events triggered much attention since there was a large commercial fishery for capelin, but also because of observed ecosystem effects ...

Changes in Barents Sea ecosystem state, 1970–2009: climate fluctuations, human impact, and trophic interactions

Johannesen, E., Ingvaldsen, R. B., Bogstad, B., Dalpadado, P., Eriksen, E., Gjøsæter, H., Knutsen, T., Skern-Mauritzen, M., and Stiansen, J. E. 2012. Changes in Barents Sea ecosystem state, 1970–2009: climate fluctuations, human impact, and trophic interactions. – ICES Journal of Marine Science, 69: 880–889. Long time-series of data from the Barents Sea (BS) are analysed to ...

The Norwegian ecosystem-based management plan for the Barents Sea

Olsen, E., Gjøsæter, H., Røttingen, I., Dommasnes, A., Fossum, P., and Sandberg, P. 2007. The Norwegian ecosystem-based management plan for the Barents Sea. – ICES Journal of Marine Science, 64: 599–602. In April 2006, the Norwegian government launched a White Paper on a new holistic management plan for the Norwegian part of the Barents Sea, including the fishery protection zone ...

Growth of Barents Sea capelin (Mallotus villosus) in relation to zooplankton abundance

Because capelin feed on zooplankton, the availability of the latter may be a limiting factor for capelin growth in at least some areas and at certain times. It was therefore hypothesized that a relationship exists between capelin growth and zooplankton biomass either in the same year or in the previous autumn. Capelin growth in a given year was more closely correlated with the ...

Assessment methodology for Barents Sea capelin, Mallotus villosus (Müller)

The methods used to assess the Barents Sea capelin, Mallotus villosus (Müller), stock have always differed considerably from those used for most other stocks. Owing to the life history characteristics of capelin (short lifespan, considerable natural mortality, including spawning mortality), sequential population analysis (VPA, etc) cannot be applied to assess stock status and to ...

Food web dynamics affect Northeast Arctic cod recruitment

Proper management of ecosystems requires an understanding of both the species interactions as well as the effect of climate variation. However, a common problem is that the available time-series are of different lengths. Here, we present a general approach for studying the dynamic structure of such interactions. Specifically, we analyse the recruitment of the world's largest cod ...

Studying spatial and trophic interactions between capelin and cod using individual-based modelling

The objective of this study was to use spatially explicit individual-based models for simulating the movement, foraging, growth, and mortality of cod and capelin in the Barents Sea in order to identify general features in their migration patterns and the consumption of capelin by cod. The individual-based models are initiated from survey data run over 1 year and validated against ...

A comparison of performance of WP2 and MOCNESS

Zooplankton biomass in the Barents Sea was monitored during 1988–97 using WP2 and MOCNESS plankton nets. These two sampling gears differ in their size and mode of operation. The plankton samples were size fractionated into three categories and the dry weight per square metre was calculated. The smallest and the medium size fractions ( 2000 μm) consisted mainly of macrozooplankton ...