We have used the most up-to-date methods for studying asp migration and habitat preferences in Emajõgi and Laeva river systems - biotelemetry and novel state of the art method - otholith micro-chemistry fingerprint method. 

Biotelemetry enables researchers to study the behaviour and migration patterns of birds, fishes and and animals over months and years and across vast distances. There are different telemetry methods available: acoustic, radio, archival, satellite and dual mode telemetry. We have used acoustic telemetry in our fish migration and behaviour studies since 2009. 

Asp deserves to be studied by a high-tech method because he is a species of special interest. Asp is:
- one of four internationally protected fish species living in the River Emajõgi;
- the only predator and also the largest domestic carp calf in Estonia (up to 10 kg);
- species requiring large and diverse habitat;
- a minor species of fish which is therefore difiicult to protect effectively.
The River Emajõgi offers the asp a worthy habitat: a 100 km-long river connects Estonia’s largest lakes: Peipsi and Võrtsjärv. In addition, larger and smaller waterbodies flow into the River Emajõgi. In the mouth, the river flows in several branches to the Lake Peipsi. There are a hundred oxbow lakes, which can be waterbodies with still or flowing water. All these bodies of water have role to play in the asp’s life, but what exactly?
We needed to find out:
- where asps are spawning, feeding, wintering;
- when they migrate and when are in stationary;
- what are the main migration routes of the asps, what bodies of water he visits during the
migration;
- how much the behaviour varies from year to year?
In order to answer these questions, it was essential to use one of the most modern methodology of science to investigate fish migration – biotelemetry.
For the detailed description of fish migration, the tagging and tracking of the asp was used by acoustic telemetry methods. In this methodology, fish will be provided with taggs transmitting individual-specific acoustic signals and monitored by manual and automatic signal receivers.

Otolith microchemical analysis is a technique used in fisheries management and fisheries biology to delineate stocks and characterize movements, and natal origin of fish. The concentrations of elements and isotopes in otoliths are compared to those in the water in which the fish inhabits in order to identify where it has been.

The main objective of the pilot study of the microchemical fingerprint of the otoliths of the River Emajõgi system was to determine whether the chemical fingerprint of the young asps originated from the Haaslava fish farm can be distinguished from the fingerprint of natural asps otoliths. 

To reveal the history of otoliths growth, the otoliths were grinded to the core (frontal cross section) and then taped to one of the slides. Microchemical analyses were carried out in two mass spectrometry laboratories. Analysis of trace elements were performed in the geology department of the University of Tartu using laser ablation with inductive-coupled plasma mass spectrometer (LA-ICPMS). Strontsium isotopes were analysed in the Vegacenter subdivision of the Swedish Natural History Museum using a multi-collector inductive plasma mass spectrometer (MC-LA-ICPMS).

Based on the material collected and analysed in this work, it can be concluded that, as a general rule, the chemical fingerprint of the otoliths of the asps from the Haaslava fish farm, is different from the chemical fingerprint of the naturally hatched fish.

An analyses of otoliths of large (43-83 cm) asps, cought in the wild showd that 16% of fish were of Haaslava fis farm oigin. This result proves that the introduction of young Fish, carried out Under the LIFE Happyfish and Happyriver projects will actually help to increase and improve the abundance of this protected species in the wild. From the juvenile asps, cought in the restored River Laeva 27% originated from Haaslava fish farm.

Strengthening the population of fish by inhabiting works has been a historically common method. The fact that there is no knowledge of the positive effect of the  work is often highlighted as a negative aspect. This innovative work came out of historical frames, using entirely natural markers of water chemistry and it was possible to reconstruct a picture of one of the most important stages of life of the fish – the time and the place of hatching. The appropiateness of the methodology with the water system under investigation has been confirmed and deserves further development.