DTU Aqua’s research into population genetics aims at gaining knowledge on how to preserve and manage biodiversity sustainably, in relation to both recreational and commercial fisheries, biodiversity conservation and aquaculture.
Knowledge is achieved through studies of the evolutionary processes responsible for generating and maintaining genetic diversity within and among populations of marine and freshwater fishes.
DTU Aqua develops and employs state-of-the-art molecular genomic tools for genetic traceability and for restoring and managing local fish populations.
Main themes within population genetics research
DTU Aqua's research into population genetics has five main themes:
- Stock identification
We describe the distribution of fish populations (stocks) and their diversity from regional to local scales. For example, how many populations of cod are there in the Baltic Sea and of eel in the Sargasso Sea? And what is the extent of genetic exchange between local populations? We determine the distribution and the size of the individual population, now and historically.
- Genetic traceability and monitoring
We develop methods for tracing the species and origin of individual fish and fish products, including the use of DNA from water samples (e-DNA) to determine the dtistribution and abundance of aquatic species in both freshwater and marine areas. We also use genetic data to:
- evaluate effects of stocking and habitat disturbance
- determine the migratory behaviour of individual fish populations
- determine which fish reproduce
- determine how we can restore endangered populations in a sustainable manner that take population histories and local adaptations into consideration.
- Local adaptation
We examine whether populations are genetically adapted to their local environments. This knowledge is used for understanding evolutionary processes in general, but is also applied as a fisheries management tool, e.g. for determining whether releases may contribute to rebuilding of endangered or locally extinct populations.
- Genetic impact of climate change
We examine whether climate change affects the distribution and the genetic composition of populations. We analyse genes related to temperature adaptation in order to determine whether local populations are likely to 1) adapt genetically, 2) alter their distribution (e.g. relocate to more northerly areas), or become extinct due to global warning.
- Genetic impacts of fisheries
We analyse DNA from historical samples to study whether fishing has affected the distribution and genetic composition of fish populations. We use the results to illustrate the impact of different types of fishing on genetic resources and to infer how fisheries can be directed to best conserve the genetic variation.
Why do we do research into population genetics?
Population Genetics focuses on describing the genetic differences between populations of fish, between the individuals within the same population and between fish in aquaculture. For example, a brown trout from one part of Denmark does usually not have the same genetic fingerprint (DNA profile) as a brown trout from another part of Denmark, just as the North Sea cod does not have the same genetic fingerprint as the Baltic Sea cod.
The genetic variation of contemporary fish populations is the result of evolutionary processes, reflecting both geographical separations of populations over thousands of years and genetic adaptation to local conditions.
The genetic differences can be analysed and described using modern DNA technologies, providing important information on the factors influencing the distribution and dynamics of fish populations. They also provide us with a technical tool for tracing individual fish and fish products back to the sea-areas or aquaculture plants from where they originated.
What is the research used for?
Population genetic analyses are used to determine the population composition of fish catches in order to avoid overexploitation of small and vulnerable fish populations. The analyses may also be used to control illegal fishing by testing whether landed fish and fish products originate from species and stocks which can legally be caught.
Genetic monitoring also plays an important role in planning the long-term management of fish resources. The work is carried out by comparing DNA from contemporary fish samples with DNA analyses of samples from historical time series.
We compare DNA from fish scales and otoliths sampled more than 100 years ago, providing insight into how wild populations have responded to stocking, fishing and environmental change. Thus, inferences from our research can be used to guide management in order to preserve the genetic variation, resulting in healthy and productive fish populations that can be exploited sustainably.