Kristine Bonnevies hus
Conservation efforts and management decisions on the living environment of our planet often rely on imperfect statistical models. Therefore, managers have to brace for the uncertainty associated with the model and study system i.e., set their acceptable risk level, to make some decisions. However, risk estimates themselves can often be biased. In a recent paper published in Nature communications we demonstrate that one can back-calculate the correct value of risk by combining data fitting with an extensive simulation–estimation procedure.
A new pan-arctic study indicates that Calanus copepods do not necessarily descend deep for diapause in winter; instead, parts of the population remain active. Moreover, the deeper distribution of the larger and more conspicuous Calanus hyperboreus indicates that predation pressure is a key trigger for diapause at depth. In the central Arctic Ocean where visual predation pressure is lower, copepods might be relieved from the incentive to descend and can remain closer to the surface in winter.
Since the very first representation of an ecological network (Camerano, 1880), food webs have become an important tool to explore and summarize the trophic interactions between species that coexist in an ecosystem. The architecture of food webs is intimately related to how ecosystems function, and determines the services ecosystems provide. Changes in the structure of food webs may have drastic consequences for the functioning of ecosystems. Yet, our understanding of how food webs vary over time remains unclear.
Accomplishing a complete inventory of species and their interactions requires significant effort, and the diversity and dynamics of nature makes it challenging to follow variability in food webs over time: species come and go, or become more or less abundant.
In this study, we asked the question: How are changes in species composition (presence/absence and abundances) influencing food web structure over time?
Extreme events in the marine environment, like marine heatwaves, are likely at least as important as changes in mean values for causing threats to biodiversity, with impacts on ecosystem services and consequences for human systems. The potential of human and natural systems to adapt to such changes remains unclear, but two recent articles in the high-impact journal PNAS look closer at the possibilities.
Population abundance depends on production of young and survival of adults. Assessing the contribution of young production to population growth and identify the main drivers of its variability may help to identify appropriate stock management measures. What happens when several stocks, belonging to different trophic levels and habitats, as well as having different exploitation histories are sharing the same environment?
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.