Age determination in fish based on DNA methylation patterns

Lead Institute FI Institute of Fisheries Ecology

Development of an alternative epigenetic method for age determination of plaice (Pleuronectes platessa).

How old is a fish really? This question plays a central role in the sustainable management of our oceans. Knowing the age of fish helps protect stocks and establish meaningful catch quotas. Traditional methods of determining fish age are invasive and usually require the animals to be killed. Our research approach relies on an innovative, gentle method to avoid this procedure.

Background and Objective

The age of a fish provides information about its life expectancy, growth, and reproduction rates. So far, age determination in fish has primarily been carried out by examining ear stones, known as otoliths, which are structures in the inner ear of the animals. However, this method is not reliably applicable to all fish species. In addition, it is time-consuming, requires specialized expertise, and involves killing the animals. In our project, we are pursuing the establishment of an alternative, molecular-biological method based on the analysis of specific methylation patterns in the animals’ DNA. Epigenetic modifications such as DNA methylation are natural chemical changes to the genetic material that regulate gene activity and change over the course of an organism’s lifetime. These modifications can be influenced by various environmental factors. The concept of an ‘epigenetic clock’ refers to the idea that certain processes in the body adjust during aging, allowing biological age to be derived. With the help of such an epigenetic clock, the age of fish could be determined precisely at the molecular level without killing the animals. Only tiny tissue samples, such as from the fin, are required for the analysis.

Approach

To develop the most universal possible epigenetic clock for plaice, samples are taken from individuals of different age classes, collected from various regions and times. From these samples, we extract DNA and prepare it in such a way that the methylation patterns can be visualized through subsequent sequencing. Using bioinformatic models, we then develop the epigenetic clock. Afterwards, this method is tested and validated with independent samples that were not used in the clock’s development.

Our Research Questions

Can the age of plaice be reliably and accurately determined using the developed epigenetic clock?
Are the methylation patterns universal enough to cover different populations and habitats?