Nettsider med emneord «Cod»

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Publisert 4. okt. 2023 08:08

Climate change and increasing human activity are increasing risks of mass mortality events. In their recent study published in the Journal of Applied Ecology, Buttay et al. (2023) have focused on perturbations that could impact the early life stage of fish. Using the Northeast Arctic cod in the Barents Sea as an example, they evaluated different mitigation strategies alleviating the effect of such dramatic events on the population.

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Publisert 24. nov. 2022 11:09

Understanding the changes in population abundance is essential to correctly manage and preserve the natural populations. Interaction between species, such as predation or competition, is an important factor affecting population dynamics. To understand population dynamics it is thus useful to study species interactions. In a recent study published in Biology Letters, we analysed the interaction between two iconic fish species of the Barents Sea: the capelin and the Atlantic cod.

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Publisert 24. jan. 2022 07:49

Over the last century, overfishing has led to the collapse of many fish stocks. Some of them, following successful management actions, have rebuilt their number but did they remain the same?  In a recent study published in Ecology and Evolution we explored the effect of collapse on the stocks ecology by testing for differences before and after.

Image of a snow crab
Publisert 25. mai 2021 14:35

The snow crab (Chionoecetes opilio) is a newly established species in the Barents Sea, increasing in both distribution and abundance in recent years. In this Arcto-Boreal sea, they encountered the most abundant Atlantic cod (Gadus morhua) stock. What happens from here?

two dell picture symbolysing cold years and warm years withe effect on cod and haddock
Publisert 10. aug. 2020 12:16

In the Boreal-Arctic seas, the two most abundant gadoid fish are the Atlantic cod (Gadus morhua) and the haddock (Melanogrammus aeglefinus). Both tend to respond to climate warming by an abundance increase and a change of distribution. Are these changes affecting how they are interacting? Statistical analysis using a state-space threshold model of acoustic and trawl survey data on cod and haddock abundance indicates that the interaction is changing with sea temperature: the cod negatively affecting the haddock when sea temperature is over 4 °C.

overlap of abudance over time between fish and plankton, fish life cycle
Publisert 12. juni 2020 13:05

We assessed the effect of the predator−prey relationship on predator survival by developing a novel metric of predator−prey overlap using spatio-temporal statistical models. We found that the amount of overlap between cod larvae (length: 11−15 mm) and their prey explained 29 % of cod recruitment variability.

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Publisert 12. juli 2019 08:06

The Atlantic cod is one of the major predator in the Barents Sea estimated to consume over 5 million tonnes of fish in 2017. In a recent paper (Holt et al. 2019) we explore the diet of this species using a unique dataset encompassing 33 years of cod stomach sampling by Russian and Norwegian scientists. This time-series is the most comprehensive available cod diet dataset to date and is crucial in helping to answer ecologically important questions on what cod eat and why  it matters for predator-prey and food-web dynamics in the Barents Sea ecosystem. 

Publisert 4. des. 2018 09:45

Where the fish are spawning is of tremendous importance for the population (see our post) but also for the industry relying on it, especially since harvesting is often concentrated on fish that aggregate for to spawn. Climate change and harvesting are known to strongly affect the fish population with effect on the spawning location. In a recent paper (Langangen et al. Global Change Biology) we explore the question: “who is the culprit of spawning location change: Climate or fishing?”

Publisert 7. mai 2018 10:28

Many heavily fished fish stocks are dominated by young and small fish. The reason is simple: the chance to reach old age is small. If the fisheries selectively target large fish, the dominance of young and small fish becomes even larger. Such skewed age and size distributions can make the fish populations more sensitive to detrimental effects of oil spills.

Publisert 16. nov. 2016 10:03
Publisert 8. nov. 2016 09:49

Spawning time and location are important factors affecting the reproductive cycle for migratory fish by potentially affecting offspring survival and growth. We examine this relationships by using a drift model for early life stages (eggs to age 1) of the Northeast Arctic cod combined with empirical estimates of spatial variation in mortality at two different life stages (Langangen et al. 2016).

Publisert 15. apr. 2016 13:31

Growing evidence suggests that the telomeres’ length (a non-coding DNA sequence localized at the end of the chromosomes) is related to individual breeding performances and survival rates in several species.

Publisert 8. mai 2015 01:00

In this study we assessed the chances of recovery of the Baltic Sea cod stock and conclude that it will never come back to the status it had more than three decades ago and that the economic losses associated to this new baseline amount to 120 million euros per year.

Publisert 27. mars 2015 01:01

Many marine fishes experience tremendous mortality during their first months of life. Understanding the causes of this mortality and why it varies from year to year has challenged fisheries ecologists for more than a century. Part of the difficulty comes from the fact that many fishes have free-floating larvae. It is therefore difficult to follow a group of fish larvae over time in the field and investigate which factors cause mortality.

Publisert 13. mars 2015 00:01

Since Hjort’s ground-breaking work, it is admitted that the survival from the egg to the first reproduction is an essential factor affecting the dynamics of fish populations (see post). Human activities around spawning ground may have an effect on the mortality of the younger age. One of such potentially risky activity is oil exploitation which is on the increase in the northern areas.

Publisert 23. jan. 2015 00:00

The year 2014 marks the 100th anniversary of the Norwegian oceanographer and biologist Johan Hjort’s ground-breaking work, Fluctuations in the great fisheries of northern Europe, viewed in the light of biological research. This anniversary was commemorated with a special issue of ICES Journal of Marine Science.

Publisert 11. nov. 2014 12:40

Understanding the interaction between species is particularly actual in marine systems where ecosystem approach of  management is desirable. This is particularly the case in high latitude systems such as the Barents Sea where climate change effect is supposed to be the strongest.

Publisert 11. nov. 2014 12:39

Mortality of pelagic eggs and larvae of marine fish is often assumed to be constant both in space and time due to lacking information. This may, however, be a gross oversimplification, as early life stages are likely to experience large variations in mortality both in time and space.