Comparison of reproductive success of cod, Gadus morhua, from the Barents Sea and Baltic 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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Seasonal variation in biomarkers in blue mussel (Mytilus edulis), Icelandic scallop (Chlamys islandica) and Atlantic cod (Gadus morhua)—Implications for environmental monitoring in the Barents Sea

Aquatic Toxicology ◽

10.1016/j.aquatox.2012.01.009 ◽

2013 ◽

Vol 127 ◽

pp. 21-35 ◽

Cited By ~ 67

Author(s):

J. Nahrgang ◽

S.J. Brooks ◽

A. Evenset ◽

L. Camus ◽

M. Jonsson ◽

...

Keyword(s):

Seasonal Variation ◽

Environmental Monitoring ◽

Mytilus Edulis ◽

Gadus Morhua ◽

Barents Sea ◽

Blue Mussel ◽

Atlantic Cod ◽

The Barents Sea ◽

Chlamys Islandica

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Pseudobranchial tumours in Atlantic cod, Gadus morhua L., from the Barents Sea

Journal of Fish Diseases ◽

10.1111/j.1365-2761.1981.tb01166.x ◽

1981 ◽

Vol 4 (6) ◽

pp. 527-532 ◽

Cited By ~ 9

Author(s):

E. C. EGIDIUS ◽

J. V. JOHANNESSEN ◽

E. LANGE

Keyword(s):

Gadus Morhua ◽

Barents Sea ◽

Atlantic Cod ◽

The Barents Sea

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Improving catch efficiency by changing ground gear design: Case study of Northeast Atlantic cod ( Gadus morhua ) in the Barents Sea bottom trawl fishery

Fisheries Research ◽

10.1016/j.fishres.2016.10.008 ◽

2017 ◽

Vol 186 ◽

pp. 269-282 ◽

Cited By ~ 4

Author(s):

Jesse Brinkhof ◽

Roger B. Larsen ◽

Bent Herrmann ◽

Eduardo Grimaldo

Keyword(s):

Gadus Morhua ◽

Barents Sea ◽

Atlantic Cod ◽

Trawl Fishery ◽

Gear Design ◽

The Barents Sea ◽

Sea Bottom ◽

Design Case ◽

Design Case Study

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Reproductive strategy of a migratory fish stock: implications of spatial variations in natural mortality

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2015-0321 ◽

2016 ◽

Vol 73 (12) ◽

pp. 1742-1749 ◽

Cited By ~ 8

Author(s):

Øystein Langangen ◽

Geir Ottersen ◽

Lorenzo Ciannelli ◽

Frode B. Vikebø ◽

Leif Christian Stige

Keyword(s):

Reproductive Strategy ◽

Early Life ◽

Gadus Morhua ◽

Barents Sea ◽

Spatial Variations ◽

Fish Stock ◽

Life Stages ◽

Early Life Stages ◽

The Barents Sea ◽

Survival And Growth

We investigate how the reproductive strategy in a migratory marine fish may be influenced by spatial variations in mortality in early life stages. In particular, we examine how spawning time and location affect offspring survival and growth. A drift model for early life stages (eggs to age 1) of the Barents Sea cod (Gadus morhua) is combined with empirical estimates of spatial variation in mortality at two different life stages. We examine seasonal and interannual differences in survival and growth in offspring originating from two spawning grounds, with the central site requiring higher migration distance, and hence cost, than the northern site. When accounting for spatially explicit mortality fields, central and northern spawned offspring have about equal survival, as do early and late spawned offspring. Furthermore, central spawned offspring grow faster and are likely to reach a larger size compared with northern spawned offspring. Our results indicate that the fitness benefit of southward migration in the Barents Sea cod is not mainly due to higher early survival of offspring, but rather due to effects of offspring acquiring a larger size.

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Potential for codends with shortened lastridge ropes to replace mandated selection devices in demersal trawl fisheries

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2021-0178 ◽

2021 ◽

Author(s):

Manu Sistiaga ◽

Jesse Brinkhof ◽

Bent Herrmann ◽

Roger B. Larsen ◽

Eduardo Grimaldo ◽

...

Keyword(s):

Gadus Morhua ◽

Barents Sea ◽

Size Selectivity ◽

The Barents Sea ◽

Alternative Solutions ◽

Trawl Fisheries

In many trawl fisheries, codend size selectivity is supplemented by adding selection devices to the gear. In the Barents Sea gadoid fishery, combining diamond mesh codends with sorting grids is compulsory. However, the use of grids increases the costs and complexity of the gear, causing discontent among fishermen and prompting researchers to seek alternative solutions. Lastridge ropes are ropes attached to the selvedges of the codend. In this study, we tested the effect of shortening the lastridge ropes of two diamond mesh codends with different mesh sizes on the size selectivity of cod (Gadus morhua), haddock (Melanogramus aeglefinnus), and redfish (Sebastes spp.). Shortening the lastridge ropes by 15% increased the mesh opening during the fishing process, which significantly improved the size-selective properties of the codends. Further, the L50 values were always higher for the codends in the short lastridge configuration. Therefore, codends with shortened lastridge ropes may be a simpler alternative to sorting grids in this fishery, and they may be applicable to many other fisheries in which additional selection devices are used.

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The northern European shelf as increasing net sink for CO<sub>2</sub>

10.5194/bg-2019-480 ◽

2020 ◽

Author(s):

Meike Becker ◽

Are Olsen ◽

Peter Landschützer ◽

Abdirhaman Omar ◽

Gregor Rehder ◽

...

Keyword(s):

Baltic Sea ◽

North Sea ◽

Barents Sea ◽

The Baltic Sea ◽

Surface Ocean ◽

The North ◽

Northern European ◽

The Barents Sea ◽

The North Sea ◽

The Baltic

Abstract. We developed a simple method to refine existing open ocean maps towards different coastal seas. Using a multi linear regression we produced monthly maps of surface ocean fCO2 in the northern European coastal seas (North Sea, Baltic Sea, Norwegian Coast and in the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded SOCAT v5 data revealed standard deviations of the residuals 0 ± 26 μatm in the North Sea, 0 ± 16 μatm along the Norwegian Coast, 0 ± 19 μatm in the Barents Sea, and 2 ± 42 μatm in the Baltic Sea.We used these maps as basis to investigate trends in fCO2, pH and air-sea CO2 flux. The surface ocean fCO2 trends are smaller than the atmospheric trend in most of the studied region. Only the western part of the North Sea is showing an increase in fCO2 close to 2 μatm yr−1, which is similar to the atmospheric trend. The Baltic Sea does not show a significant trend. Here, the variability was much larger than possibly observable trends. Consistently, the pH trends were smaller than expected for an increase of fCO2 in pace with the rise of atmospheric CO2 levels. The calculated air-sea CO2 fluxes revealed that most regions were net sinks for CO2. Only the southern North Sea and the Baltic Sea emitted CO2 to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.

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