Aarhus University Seal / Aarhus Universitets segl

Fish and fisheries ecology

Denne side er under udvikling

Fishes are ecologically important components of the marine food webs. At the same time, we harvest more than 80 mio tons of fish and shellfish per year with great impact on the biomass, size/age-composition and life history traits of the populations. Interacting with the effects of harvesting, environmental change influences the availability of prey, predators and the physiology of the fishes and through this changes the behavior (e.g. migrations, spawning time) and energy allocation of the individuals.

Our research aim to understand and predict the consequences of harvesting and environmental change on life histories, distribution and production and to come up with relevant management actions for the sustainable use of fish resources.

To investigate the consequences of harvesting and environmental change, we use a suite of different tools and approaches. We examine diets of fishes to examine the impact of changes in prey communities. We look at the accumulation of energy, especially lipids, as indicators of the reproductive and growth potential of fishes. We work with fish population geneticists to explore genetic change and we work with modelers to explore the larger scale consequences.

One of our main tools to gather the necessary knowledge is fish otoliths (earstones). Otoliths are like flight recorders. They constantly record the age and growth of the fish through the daily and annual growth rings. At the same time they record the physical environment by incorporating chemical elements from the water that allow us to infer the salinity, temperature and the actual water mass the fish has been swimming in.  Recently, we have developed two new techniques that significantly add to the otolith toolbox. First, we developed a technique that allow us to also use the protein contained in the otolith to gain insight into the trophic position of the fish using stable isotopes, thereby allowing us to look at e.g. historical changes in the marine food webs. Now we have shown that we can also use the calcium carbonate, which makes up >90% of the otolith, as a built in fitness watch that continuously records the metabolism of the fish. This allow us to explore the consequences of warming oceans on the physiology of free living fishes, to test the effects of selective harvesting on the physiological traits of fish populations plus a number of other hypotheses based on the impact of fishing and environment on the physiological performance of fishes.

While we do research in almost all types of marine environments, our focus the last ca 5 years has been on the North Atlantic and the Arctic. We do extensive fieldwork and have close collaboration with colleagues in Greenland, the Faroes Island, UK and Norway centered on understanding processes in these areas.

Contact: Peter Grønkjær