According to a study by biologists from the University of Surrey in the UK, eels traveling to reproduction from the European rivers to the Sargasso Sea take into account the place of residence of their partner and, if possible, are associated with the eels around them.
The microsatellites repeat series of two to four letters (for example ...ACTACTACT...). The length of these microsatellites varies greatly from one individual to another, as it is very repetitive and there are often errors in copying. That is why they are very useful as a fingerprint. Surrey's biologists analyzed the microsatellites of 611 eels and, according to their length, were able to tell where each eel came from.