A baseline study of levels of mercury, arsenic, cadmium and lead in Northeast Arctic cod (Gadus morhua) from different parts of the Barents Sea

For the large Arcto-Norwegian stock of cod (Gadus morhua L.) in the Barents Sea, year-to-year variability in growth is well documented. Here three hypotheses for the observed inverse relation between abundance and the mean length-at-age of juveniles (ages 14) are suggested and evaluated. Based on comprehensive data, we conclude that year-to-year differences in length-at-age are mainly determined by density-independent mechanisms during the pelagic first half year of the fishes' life. Enhanced inflow from the southwest leads to an abundant cohort at the 0-group stage being distributed farther east into colder water masses, causing lower postsettlement growth rates. We can not reject density-dependent growth effects related to variability in food rations, but our data do not suggest this to be the main mechanism. Another hypothesis suggests that lower growth rates during periods of high abundance are a result of density-dependent mechanisms causing the geographic range of juveniles to extend eastwards into colder water masses. This is rejected mainly because year-to-year differences in mean length are established by age 2, which is too early for movements over large distances.

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Marine mammals' influence on ecosystem processes affecting fisheries in the Barents Sea is trivial

Biology Letters ◽

10.1098/rsbl.2008.0628 ◽

2009 ◽

Vol 5 (2) ◽

pp. 204-206 ◽

Cited By ~ 4

Author(s):

Peter J Corkeron

Keyword(s):

Marine Mammal ◽

Marine Mammals ◽

Gadus Morhua ◽

Fishery Management ◽

Barents Sea ◽

Scientific Evidence ◽

Primary Component ◽

Clupea Harengus ◽

Balaenoptera Acutorostrata ◽

The Barents Sea

Some interpretations of ecosystem-based fishery management include culling marine mammals as an integral component. The current Norwegian policy on marine mammal management is one example. Scientific support for this policy includes the Scenario Barents Sea (SBS) models. These modelled interactions between cod, Gadus morhua , herring, Clupea harengus , capelin, Mallotus villosus and northern minke whales, Balaenoptera acutorostrata . Adding harp seals Phoca groenlandica into this top-down modelling approach resulted in unrealistic model outputs. Another set of models of the Barents Sea fish–fisheries system focused on interactions within and between the three fish populations, fisheries and climate. These model key processes of the system successfully. Continuing calls to support the SBS models despite their failure suggest a belief that marine mammal predation must be a problem for fisheries. The best available scientific evidence provides no justification for marine mammal culls as a primary component of an ecosystem-based approach to managing the fisheries of the Barents Sea.

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Temperature conditions of development juvenile NEA cod in the Barents sea for 1998-2015 on the basis of satellite data

10.5194/egusphere-egu2020-1350 ◽

2020 ◽

Author(s):

George Vanyushin ◽

Tatyana Bulatova

Keyword(s):

Life Cycle ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Satellite Data ◽

Barents Sea ◽

Sea Surface ◽

Arctic Cod ◽

Norwegian Sea ◽

Temperature Conditions ◽

The Barents Sea

Temperature conditions of development juvenile NEA cod in the Barents sea for 1998-2015 on the basis of satellite dataVanyushin G. P., Bulatova T. V.Russian Federal Research Institute of Fisheries and Oceanography (VNIRO)107140 17, V. Krasnoselskaya str., Moscowtel: 8(499)264-01-33, fax: 8(499)264-91-87,e-mail: [email protected]&#160;AbstractThe paper considers the real temperature conditions in the main spawning area of North-East Arctic cod in the Norwegian sea and the development of its juveniles in the Barents sea in the periods from March to October 1998-2015. Here was taken as a principle the analysis of materials Bank mean weekly maps of sea surface temperature (SST) built on complex process: infrared digital data from metrological satellites of the series "NOAA" and quasisynchronous temperature data "in situ" from ships, buoys and coastal stations. A continuous series of indicators on temperature variability in the surface layer of sea water in coastal zone of the Norwegian sea during spawning periods and later on during the early ontogenesis of juvenile cod in the Barents sea &#160;allowed to establish the dynamics of interannual seasonal temperature trends on a mesoscale period of time (1998-2015). This made it possible to assess the indirect impact of temperature conditions on the prospect of survival and, accordingly, the number of juvenile cod in the first year of its life after spawning &#8211; the most important stage in the life cycle of a new generation of cod. The paper presents calculations of monthly and seasonal average values of SST and SST anomalies in the Norwegian and Barents seas, shows the interannual seasonal dynamics of these characteristics. Given for these years, the results of the comparative analysis between: seasonal values of temperature in the water surrounding the Lofoten Islands (March-April &#8211; time of the main spawning) and in the water of the Barents sea (May-October - time of the early onthogenesis of juvenile cod) and professional expert estimates the number of yearlings cod. The relationship between these statistical data was positive and about equal to R= + 0,67. Information on the number of generations of cod at different stages of its life cycle was taken from the annual reports of the Arctic Fisheries Working Group ICES.Keywords: satellite monitoring, sea surface temperature (SST), the&#160; Northeast Arctic cod, main spawning and habitat waters, yearlings of the cod.

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