Researchers at the Department of Fisheries Research and Development of MATE Institute of Aquaculture and Environmental Safety have, for the first time, bred Danube lampreys (Eudontomyzon mariae) and released their offspring into the wild. To the best of current knowledge, this represents the first conservation-oriented reintroduction initiative of its kind for the species worldwide.

Capture of broodstock using electrofishing equipment, River Rába
Photo: Tamás Müller

Lampreys are among the most ancient vertebrates still living today, having changed very little in their form and life cycle over the past 360 million years. Their bodies are eel-like and scaleless; they have no jaws, and their mouths contain characteristic sucker-like teeth. Another distinctive feature is that their reproductive organs are unpaired, their muscle fibres are not segmented, and their development has preserved several ancient characteristics.

Body weight measurement of an anaesthetised female before egg stripping
Photo: József Horváth

It is assumed that adult individuals live on the energy reserves used during spawning and then die after reproduction. The larvae feed on detritus and, after three to five years of development, undergo metamorphosis, forming their short-lived sexually mature adult form.

Sperm stripping onto one of the egg batches
Photo: Ádám Varga

In Hungary, the Danube lamprey is a strictly protected endemic species. According to experts, ex situ conservation biology research on this species has not previously been conducted anywhere in the world. Between 2025 and 2026, within the framework of an NKFI Advanced project (No. 150916), researchers from the MATE Department of Fisheries Research and Development  and the Danube-Ipoly National Park collected sexually mature individuals from the River Rába. Using hormonally induced propagation and naturally matured individuals, the researchers successfully collected gametes through egg and sperm stripping.. The egg batches were fertilised using a so-called dry fertilisation method, after which the embryos and larvae were reared to different developmental stages.

Egg stripping of Danube lamprey
Photo: András Tóth

Over the two-year period, eggs containing 18–23-day-old embryos shortly before hatching, as well as larvae a few days old, were transported back to the original spawning site of the parent individuals. The aim was to allow pre-reared larvae, protected from egg predators, to continue their development in their natural habitat.

18-day-old lamprey embryos shortly before larval hatching
Photo: Tamás Müller

According to MATE researchers, this is the first conservation-oriented reintroduction activity of its kind in the world for the Danube lamprey.

Danube lamprey larva – 55 days after fertilisation, 37 days after hatching
Photo: Dr. Bence Ivánovics

Over the two years, the researchers reintroduced a total of 10,105 individuals, representing a conservation value of more than HUF 1 billion. It is important to note that, in cooperation with Hungarian and international partner institutions — Eötvös Loránd University, Ludovika University of Public Service, Kanazawa University and the University of Birmingham — research is still ongoing into the reproductive biology of the species. This work is significant not only from an evolutionary biology perspective, but also has direct conservation importance.

Release of offspring at the parents’ spawning site
Photo: Tamás Müller