I am fascinated by how processes at the individual level feed into patterns at the population level and further in communities and ecosystems – including humans.
I have always been interested in applied questions, and I strive for keeping my research in what is know as the Pasteur’s quadrant – research motivated by both fundamental understanding and utility to society. I often combine insights from evolutionary ecology into management related questions, providing new insight into old problems. I am keen on finding sustainable solutions for using our natural resources and feeding the growing human population.
My main research tool is simulation modelling, trying to build models incorporating mechanistic understanding and often evolutionary considerations. I like to see the theoretical modelling work intertwined with field and experimental data, forming an iterative modelling-data-modelling cycle. Throughout this cycle, model predictions are confronted with observational data to refine hypotheses and mechanistic models, at the same time also generating suggestions for new experiments and data collection.
I have carried out research on relatively wide range of topics, and and below I have tried to sort my work within different, although in some occasions overlapping, categories. You can also have a look at the full list of my Publications.
Contemporary and fishing-induced evolution
Natural selection is a key force of evolution. The individuals that survive to reproduce will get their genes further to the next generation. For many fished stocks mortality caused by fishing is actually higher than the natural mortality, and leads to artificial selection. If the changes caused by this artificial selection are heritable, fishing-induced (or fisheries-induced) evolution is taking place. Unlike commonly assumed, strong selection pressure can lead to observable evolutionary changes within only few generations, thus the term contemporary evolution. I have mostly worked on evolution of life-history traits, such as maturation age and size, growth patterns, reproductive investment, and mortality schedules, which cause differences in the life cycles of organisms, and together form life-history strategies, and are important determinants of fitness, a central element of Darwinian evolution. I have also investigated how behavioural selectivity drives life-history evolution.
Selected publications on this theme: I was the main PhD-supervisor of M. Claireaux in 2015-2019.
Stock assessment and fisheries management
Sustainable use of marine resources requires that we are able to access the status of these resources – otherwise we are not able to judge the status of the populations. Stock assessments use catch and survey data to estimate the population size, and this estimate of population size is further used in harvest control rules to give advice on fisheries quotas. Fisheries management is very dependent on modelling work, for estimating the population size, forecasting how different quotas will affect the population, and for running management strategy evaluations where different potential management measures and reference points are evaluated.
Selected publications on this theme: F. Zimmermann was a postdoc in my lab in 2015-2019.
Fish growth, reproduction, and bioenergetics
Most fish are indeterminate growers, meaning that unlike for example humans, who pretty much stop growing (at least in length) after reaching adulthood, fish tend to grow for many years after reaching maturity. However, investing energy and resources into reproduction reduces the energy available for somatic (body) growth, so maturing early usually means smaller adult size compared to the later-maturing individuals. This flexibility however gives fish an extra degree of freedom in their life-history strategies, because same life-time fitness can be reached by maturing earlier and reproducing over many years, or by waiting until larger size before reproducing, and then have a higher reproductive output in those fewer occasions of reproduction. Therefore it is not always easy to foresee for example the evolutionary consequences of increased mortality, particularly if the mortality is selective – as fisheries virtually always are.
Selected publications on this theme: I was the main PhD-supervisor of M. Claireaux in 2015-2019.
Population dynamics and distribution
None of natural populations are stable, they are all dynamic and continuously changing in structure, size, and distribution. The changes in population size are governed by births and deaths, and emigration and immigration. In addition, these processes are often dependent on the population abundance – for example, with high abundance, there will be more competition for resources, and that might lead to decreased birth rates or increased death rates. Since I work a lot with fish, I have worked with particularly recruitment dynamics, that is, how many new individuals enter the population each year, and what are the factors influencing this. Many fish stocks have been at low levels due to overexploitation, and I have tried to understand the recovery process of such populations after the fishing mortality has been reduced.
Selected publications on this theme: F. Zimmermann & N. Nikolioudakis were both postdocs in my lab in 2015-2019.