Kristine Bonnevies hus
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.
What does it mean when an economist talks about field work? What is experimental economics? How do you do experiments when your sample are humans? If those questions are on your mind then this little text is for you.
Climate effects on marine ecosystems are often projected as a bottom-up process. That is, the focus of the projections is often: How do changes in physical conditions and biogeochemical processes at lower trophic levels influence living conditions for fish and other organisms at higher trophic levels? However, this view ignores feedbacks between higher and lower trophic levels.
How can two drivers, fishing pressure and climate change, interact in inducing discontinuous dynamics in 20 Atlantic cod stocks? And how can these dynamics affect stocks´ recovery? We are trying to solve this mystery in our new paper1 published in Proceeding of the Royal Society B!
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?”
Late last month, the Intergovernmental Panel on Climate Change issued a Special Report on the Impacts of Global Warming of 1.5 ºC1 above pre-industrial levels (a rather low-emission pathway), triggering a lot of discussions around its origins and impacts on natural and human systems. In this context, it would be interesting to see how the ocean is likely to respond under - what is considered today as - an "optimistic" scenario for greenhouse gas emissions in the future, relative to more severe projections. Particularly for regions vulnerable to climate change (or else "Hot Spots") like the Mediterranean Sea, such a comparison would be more meaningful to be performed for the anomalous sea surface temperatures rather than the mean temperature evolution. And if you wonder why, let’s dive into the next paragraph.
Summer often means it is field season for biologists, and time to get your hands dirty! Here I will give my view of what it is like to be on board of a research vessel in the North Sea, participating in a scientific survey of the fish and invertebrates living on the sea floor.
The extensive spawning migration of Northeast Arctic cod was suggested to be counterbalanced by increased early-offspring survival, however we find in a study published in July in Marine Ecology Progress Series, that early offspring growth should be considered as another factor explaining this long-distance migration.
Why do organisms have different shapes? The morphology of species is not random, but the result of a long process of evolution and adaptations to the species’ environment and behaviours. Fish show a large diversity in shapes (e.g. flat fish, eel-like, torpedo-shaped), but how to measure such a diversity? In other words, how to compare objectively the shapes of fish found across an ecological gradient? Those are the questions that Caillon and coauthors tried to answer in a study recently published in Ecosphere (DOI 10.1002/ecs2.2220).
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.
Spawning migration is a prevalent phenomenon for the major fish stocks in the Barents Sea. While many of them migrate to the coast of Norway to spawn they are doing so to different areas. We have studied the Northeast Arctic haddock variability in spawning grounds to understand what drives the observed shifts over time.
Derivatives, Integrals, Optimal Control Theory, Calculus… as an ecologist (and in particular an empirical ecologist) these terms can be frightening. However, we need to face our fears to take a step towards interdisciplinarity!
Fishing is one of the most physically  and economically  risky activities one can engage in. According to the Bureau of Labor Statistics of the United States, fishing and related activities has the second highest rate of workplace fatalities (logging is ranked first) . Today however, we will exclusively focus on the economic risks fishers and their communities face and how fish themselves are a unique natural resource.
The festivities of Saint Valentine´s day are upon us, and this coincides with the arrival of the Northeast Arctic cod to the shores of mainland Norway for spawning, a fish close to the heart of Norwegians. This fish is also known as Barents Sea cod, or in Old Norse skreið, modern Norwegian skrei. Skrei might be one of the earliest recognised subtypes of cod, but not until the 20th and 21st Century have researchers been able to start pinpointing exactly how it is different from other local cod, with the aid of modern sequencing technology.
In a study recently published in Ecology we find apparent competition between major zooplankton groups in a large marine ecosystem. Apparent competition is an indirect, negative interaction between two species or species groups mediated by a third species other than their prey.
In my last post, I explained why resolution matters in food webs. However, I never properly introduced what is a food web and how to build them.
Atlantic cod (Gadus morhua) is an iconic fish species world-wide. How did such a fish become THE FISH? And, in the future, will we still be able to have cod on our table as Christmas delicacy?
Understanding the spatio-temporal dynamics of biotic communities (i.e. knowing when and where different species are) is crucial for the management and conservation of ecosystems. We promote the use of an advanced statistical method, called ‘tensor decomposition’, to reveal the spatio-temporal dynamics of species assemblages using the multidimensionality of collected data set (see study by Frelat et al. 2017).
The concept of ecosystem-based management (EBM) has become popular for marine research and management in recent years. While there is no commonly accepted definition of EBM, “holistic” is one of the common descriptions for such approach. Why do we need a holistic approach? Let us take salmon as an example. Imagine you are a salmon that was born in a river of a Northern Baltic country. What kind of life would that be?
Marine systems are characterised as highly complex, being subject to multiple drivers (e.g. climate change or fishing pressure) and being riddled by high uncertainties. Yet, we still manage to come up with models to simulate ecosystem dynamics or establish fishing quotas. In order to achieve this we rely on experts and their judgements. Especially in situations where empirical data is scarce experts are often the best or even only source of information. Experts help to make sense of ambiguous data or, in case of no data, are able to provide input due to their acquired learning and experience. These expert judgments are indispensable but it pays to be aware that they are not perfect. While the idea that people are not always rational agents has been widely accepted, it is often overlooked that experts are humans, too.
Many animals migrate for various reasons, for instance to find new feeding grounds, survive harsh climate, or reproduce. Northeast Arctic cod is a fish that is of high economic importance to Norway and Russia and which undertakes annual migrations. Here, I will talk about its spawning migration and highlight some of its costs and benefits.
The upcoming Brexit has European fishermen worrying that they cannot continue to fish in British waters as they have been doing for centuries. If British waters would truly be closed to European fishermen, it would deal a strong blow to the European fisheries, since many fish are caught in British waters. Here we raise the questions: do fish really care about these country borders, and is it valid from a biological viewpoint for the UK to claim ‘their fish’?
Since Hjort in 1914 it is accepted that recruitment variation is a major source of variability in the biomass of adult fish. In a recent study published in Marine Ecology Progress Series (Durant & Hjermann 2017) we investigated how external forcing and age structure alter the effect of the year-to-year recruitment variability on population growth for some key fish species which occupy different trophic levels in an Arcto-boreal marine ecosystem.
For the second time this summer, an intense heat spell is on the rise in many European countries as temperatures go beyond 40 C. Official heatwave warnings and instructions are issued repeatedly for european citizens who often flee to the sea breeze to cool off. But exactly how cold is the water that we are turning to for a bit of comfort in days like that? We are all familiar with the idea of global warming, but have you ever wondered what happens once such extreme heat penetrates the sea surface into the marine world? Does the ocean ever develop heatwave ''fever ''?
Past studies on high-latitude abundances and distributions shifts under climate change have largely focused on food availability and temperature. In a new model linking physics to biology, published in Global Change Biology, we quantify how sea-ice loss will improve visual fish foraging efficiency. Ecological and evolutionary consequences for polar marine ecosystems would follow.