scholarly journals Diets of the Barents Sea cod (<i>Gadus morhua</i>) from the 1930s to 2018

2021 ◽  
Vol 13 (3) ◽  
pp. 1361-1370
Author(s):  
Bryony L. Townhill ◽  
Rebecca E. Holt ◽  
Bjarte Bogstad ◽  
Joël M. Durant ◽  
John K. Pinnegar ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Visual Analysis ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Fish Diet ◽  
The North ◽  
The United Kingdom ◽  
Federal Research ◽  
The Barents Sea ◽  
The Uk

Abstract. A new dataset on the diet of Atlantic cod in the Barents Sea from the 1930s to the present day has been compiled to produce one of the largest fish diet datasets available globally. Atlantic cod is one of the most ecologically and commercially important fish species in the North Atlantic. The stock in the Barents Sea is by far the largest, as a result of both successful management and favourable environmental conditions since the early 2000s. As a top predator, cod plays a key role in the Barents Sea ecosystem. The species has a broad diet consisting mainly of crustaceans and teleost fish, and both the amount and type of prey vary in space and time. The data – from Russia, Norway and the United Kingdom – represent quantitative stomach content records from more than 400 000 fish and qualitative data from 2.5 million fish. Many of the data are from joint collaborative surveys between Norway and Russia. The sampling was conducted throughout each year, allowing for seasonal, annual and decadal comparisons to be made. Visual analysis shows cod diets have changed considerably from the start of the dataset in the 1930s to the present day. There was a large proportion of herring in the diets in the 1930s, whereas in more recent decades capelin, invertebrates and other fish dominate. There are also significant interannual asynchronous fluctuations in prey, particularly capelin and euphausiids. Combining these datasets can help us understand how the environment and ecosystems are responding to climatic changes, and what influences the diet and prey switching of cod. Trends in temperature and variability indices can be tested against the occurrence of different prey items, and the effects of fishing pressure on cod and prey stocks on diet composition could be investigated. The dataset will also enable us to improve parametrization of food web models and to forecast how Barents Sea fisheries may respond in the future to management and to climate change. The Russian data are available through joint projects with the Polar Branch of the Russian Federal Research Institute of Fisheries and Oceanography (VNIRO). The UK and Norwegian data (Townhill et al., 2020) are being released with this paper at https://doi.org/10.21335/NMDC-2139169383.

scholarly journals Diets of the Barents Sea cod from the 1930s to the present day

2020 ◽  
Author(s):  
Bryony L. Townhill ◽  
Rebecca E. Holt ◽  
Bjarte Bogstad ◽  
Joël M. Durant ◽  
John K. Pinnegar ◽  
...  
Keyword(s):  
Visual Analysis ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Fish Diet ◽  
The North ◽  
The United Kingdom ◽  
The Barents Sea ◽  
Commercially Important ◽  
The Uk

Abstract. A new dataset on the diet of Atlantic cod in the Barents Sea from the 1930s to the present day has been compiled, to produce one of the largest fish diet datasets available globally. Atlantic cod is one of the most ecologically and commercially important fish species in the North Atlantic. The stock in the Barents Sea is by far the largest, as a result of both successful management and favourable environmental conditions since the early 2000s. As a top predator, cod plays a key role in the Barents Sea ecosystem. The species has a broad diet consisting mainly of crustaceans and teleost fish, and both the amount and type of prey vary in space and time. The data, from Russia, Norway and the United Kingdom, represents quantitative stomach contents records from more than 400,000 fish, and qualitative data from 2.5 million fish. Much of the data is from joint collaborative surveys between Norway and Russia. The sampling was done throughout each year allowing for seasonal, annual and decadal comparisons to be made. Visual analysis shows cod diets have changed considerably from the start of the dataset in the 1930s to the present day. There was a large proportion of herring in the diets in the 1930s, whereas in more recent decades, capelin, invertebrates and other fish dominate. There are also significant interannual asynchronous fluctuations in prey, particularly capelin and euphausiids. Combining these datasets can help us understand how the environment and ecosystems are responding to climatic changes, and what influences the diet and prey switching of cod. Trends in temperature and variability indices can be tested against the occurrence of different prey items, and the effects of fishing pressure on cod and prey stocks on diet composition could be investigated. The dataset will also enable us to improve parametrisation of food web models, and to forecast how Barents Sea fisheries may respond in the future, to management and to climate change. The Russian data is available through joint projects with Polar branch of VNIRO. The UK and Norwegian data (Townhill et al., 2020) is being released with this paper at https://doi.org/10.21335/NMDC-2139169383.

Movements and distribution of cod (Gadus morhua) in the southern North Sea and English Channel: results from conventional and electronic tagging experiments

2007 ◽  
Vol 87 (2) ◽  
pp. 599-613 ◽  
Author(s):  
David Righton ◽  
Victoria Anne Quayle ◽  
Stuart Hetherington ◽  
Gary Burt
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
English Channel ◽  
Seasonal Movement ◽  
Southern North Sea ◽  
The North ◽  
Fisheries Policy ◽  
The Uk ◽  
Electronic Tags

The sub-structure of Atlantic cod (Gadus morhua) stocks in the North Sea has important consequences for fisheries management as the Common Fisheries Policy moves towards a more regional approach. We investigated the movements, distribution and behaviour of cod in the southern North Sea (ICES IVc) and English Channel (ICES VIId) by re-analysing historic data from conventional tagging experiments, and by conducting new experiments with electronic tags. Cod tagged and released in IVc showed a northwards shift in distribution during the feeding season consistent with a homing migration away from spawning grounds along the coasts of the UK and the Netherlands. In contrast, cod tagged and released in VIId did not exhibit a consistent pattern of seasonal movement. Many cod released in VIId were subsequently recaptured close to their release position, although some moved out of the Channel and into the southern North Sea. Overlap between the recapture areas of cod released in the different management areas was no more than 25% in either the spawning or feeding season. Behavioural data from electronic tags suggest that cod in IVc make use of tidal streams to migrate northwards and eastwards in spring, whereas selective tidal stream transport was rarely exhibited by cod tagged and released in VIId. Overall, the evidence suggests that there are behavioural differences between cod in IVc and VIId that limit the mixing of cod from these two areas during the feeding and spawning seasons.

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

1981 ◽  
Vol 4 (6) ◽  
pp. 527-532 ◽  
Author(s):  
E. C. EGIDIUS ◽  
J. V. JOHANNESSEN ◽  
E. LANGE
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
The Barents Sea

scholarly journals Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys

2009 ◽  
Vol 66 (6) ◽  
pp. 1225-1232 ◽  
Author(s):  
Viacheslav A. Ermolchev
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Biological Data ◽  
Target Strength ◽  
Fish Length ◽  
The Barents Sea ◽  
Total Fish ◽  
Acoustic Surveys

Abstract Ermolchev, V. A., 2009. Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys. – ICES Journal of Marine Science, 66: 1225–1232. This paper presents methods for collecting acoustic and biological data, including in situ target-strength (TS) estimates of fish, with results presented for Atlantic cod (Gadus morhua) obtained from combined trawl-acoustic surveys. These include fish in the small, average, and maximum length classes, within the range 5–136 cm (total fish length, LT). The investigations were done using Simrad EK500/EK60 echosounders with split-beam transducers and special post-processing software. Based on an analysis of data collected in the Barents Sea during 1998–2007, a relationship TS = 25.2 log10(LT) − 74.8 was obtained for Atlantic cod at 38 kHz, with TS in dB and LT in centimetres. Seasonally, and for depths between 50 and 500 m, the variability in cod TS was 3.1 dB, decreasing with depth. The largest day–night difference in mean TS was in August–September, with changes as large as 1.0–1.7 dB. In the other seasons, the day–night difference was <1.0 dB.

scholarly journals Barents Sea cod (Gadus morhua) diet composition: long-term interannual, seasonal, and ontogenetic patterns

2019 ◽  
Vol 76 (6) ◽  
pp. 1641-1652 ◽  
Author(s):  
Rebecca E Holt ◽  
Bjarte Bogstad ◽  
Joël M Durant ◽  
Andrey V Dolgov ◽  
Geir Ottersen
Keyword(s):  
Gadus Morhua ◽  
Trophic Ecology ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Prey Size ◽  
Ecosystem Dynamics ◽  
Polar Cod ◽  
Important Species ◽  
Predator Prey ◽  
The North

Abstract Atlantic cod (Gadus morhua) is an ecologically and commercially important species in the North-Atlantic region. Cod is a top predator and information on its trophic ecology is integral for understanding predator–prey relationships and food-web dynamics. We present an analysis of the trophic patterns of Barents Sea (BS) cod using a unique 33-year time-series of stomach-content data from 1984 to 2016. We assessed patterns in diet (prey) composition across years, between seasons, as well as ontogenetic trends in diet, including predator–prey size relationships. Ontogenetic shifts in diet were observed, with fish becoming more important prey with increasing cod size. A very early onset of piscivory was found in &lt;20 cm cod. Cannibalism was found in cod &gt; 20 cm and increased with size. Juvenile cod exhibit a tendency towards consuming prey up to 33% of their body length, whereas larger cod feed on all prey sizes, resulting in asymmetric predator–prey size distributions. Diet varied significantly during 1984–2016, consistent with changes in both prey, cod abundance, and distribution. Seasonal differences were observed; capelin dominated the winter diet, whereas cod, polar cod, and other fish species were prevalent in summer/autumn months. This work represents an important step towards understanding trophic linkages that determine BS ecosystem dynamics.

Understanding limits to cod and haddock separation using size selectivity in a multispecies trawl fishery: an application of FISHSELECT

2011 ◽  
Vol 68 (5) ◽  
pp. 927 ◽  
Author(s):  
Manu Sistiaga ◽  
Bent Herrmann ◽  
Kåre N. Nielsen ◽  
Roger B. Larsen
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Morphological Characteristics ◽  
Melanogrammus Aeglefinus ◽  
Size Selectivity ◽  
Sea Trial ◽  
Trawl Fishery ◽  
The Barents Sea ◽  
Morphological Differences

This investigation demonstrates how a multidisciplinary approach based on the FISHSELECT framework, sea trial data, underwater recordings, and laboratory investigations of netting can be applied to size selectivity studies and related management issues. We studied the morphological characteristics of Atlantic cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) in the Barents Sea bottom trawl fishery. The differences between the L50 values (i.e., the size at which a fish has a 50% chance of being retained) that were recorded for the two species during sea trials can to a large extent be explained by the morphological differences between them. Because of these morphological differences, L50 is always larger for cod than for haddock with the grid and codend setup commonly used in the area. While catch separation of cod and haddock is a management objective in the Barents Sea, we demonstrate that the morphological differences between the species and the grid and codend setup in force today limit achievable differences in L50 to 5.5 cm. Furthermore, we show that for this fishery, the scope for increasing L50 differences between these species by changing the mesh shape configuration of the codend is minimal.

scholarly journals Ontogenetic development of otolith shape during settlement of juvenile Barents Sea cod (Gadus morhua)

2017 ◽  
Vol 74 (9) ◽  
pp. 2389-2397 ◽  
Author(s):  
Christian Irgens ◽  
Olav S Kjesbu ◽  
Arild Folkvord
Keyword(s):  
Body Condition ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Late Summer ◽  
Simple Method ◽  
Fish Size ◽  
Otolith Shape ◽  
Reduced Body ◽  
The Barents Sea

Abstract This study documents how settlement of juvenile Atlantic cod (Gadus morhua) in the Barents Sea affects otolith growth and morphology. A simple method to objectively discriminate between age 0 and age 1 cod sampled in late summer was demonstrated by using only two otolith morphometric descriptors: area and perimeter. In the pre-settled 0-group cod, otolith lobe formation clearly increased with fish size, resulting in high otolith crenulation. This trend was disrupted during settlement, resulting in noticeably less crenulated otoliths of the settled 1-group cod sampled in winter. Combined observations of otolith shape, fish size, and body condition suggest that environmental factors associated with settlement during autumn, particularly reduced food intake, directly affect lobe formation leading to less crenulated otoliths. Comparably reduced body condition and otolith crenulation of 0-group cod in bottom trawls (vs. pelagic trawls) may indicate early settlement or vertical exploratory behaviour in the Barents Sea Ecosystem Survey (in August–September) and, thus, an underrepresentation of 0-group cod from pelagic trawling.

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