Creating fish semen banks improves breeding, says researcher

Photo from the Institute of Animal Reproduction and Food Research PAS press release.
Photo from the Institute of Animal Reproduction and Food Research PAS press release.

Supporting the process of fish reproduction in the event of an ecological disaster, securing the stability of breeding in fish hatcheries and protecting the gene pool - these are the main objectives of fish semen banks, which are being established by scientists from the Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences in Olsztyn.

'Awareness of the need for fish semen banks continues to grow. Last year’s ecological disaster on the Oder River in Poland made us realise how important it is to have backup to be able to start the process of reproduction of native fish populations efficiently and effectively in such situations,’ says Dr. Sylwia Judycka from the Department of Gamete and Embryo Biology of the Institute of Animal Reproduction and Food Research PAS.

dr Sylwia Judycka z Zakładu Biologii Gamet i Zarodka IRZiBŻ PAN. Fot. materiały prasowe
Dr. Sylwia Judycka from the Department of Gamete and Embryo Biology of the Institute of Animal Reproduction and Food Research PAS. Photo from press release.

In addition to protecting endangered species or entire fish populations, semen banks also make it possible to safeguard the stability of breeding lines in fish hatcheries. As part of a Polish National Centre for Research and Development project, Dr. Judycka worked on the creation of a fish semen bank for the largest facility of this type in Poland, located in Dąbie (Dąbie Fish Hatchery). 

'Having frozen semen greatly improves breeding in various situations, e.g. when sexual maturity of females and males does not occur at the same time for various reasons, or when a breeding farm does not have sexually mature males in a certain year, making it impossible to obtain fresh semen for spawning, Judycka says.

Supporting efficiency in breeding is not the only reason for having a fish semen bank. 'Disasters can also occur on farms, when a virus dangerous for fish is detected in the water. In such situations, unfortunately, the entire stock of the farm has to be disposed of. It can take years to rebuild it by natural means; with frozen semen of valuable breeding lines, the process will be much quicker,’ Judycka says. 

According to the researcher, currently the main obstacle to having a fish sperm bank is the financial barrier: the cost of creating such a bank and maintaining it.

Fish semen is cryopreserved (stored at an ultra-low temperature of -196°C) before being deposited in the bank. 'We fill thin straws, several centimetres long, with semen; they are frozen on special frames in liquid nitrogen vapour and then transferred to liquid nitrogen containers. Each straw with a sample of frozen semen is accurately labelled, which enables the frozen semen samples to be correctly identified and has a specific number of sperm per millilitre.

‘The shelf life of semen frozen and stored in this way is calculated to be up to thousands of years. So far, we have tested semen thawed after several years and it was still of high quality.'

Dr. Judycka's research interests include studies of fish semen - its quality, and learning about the mechanisms responsible for such processes as the maturation of spermatozoa in rainbow trout neo-males (neo-males are sex-reversed fish). The main method used in her research is the aforementioned cryopreservation.

Dr. Judycka’s recent scientific publications have included the development of guidelines for improving the cryopreservation process and semen quality assessment of sex-reversed salmonids.

In September, the researcher starts a three-month research internship in France (at the Laboratory of Fish Physiology and Genomics of the INRAE in Rennes) to learn about a research technique called gene editing and be able to use it later in her further research.

For her scientific achievements, Dr. Judycka was awarded the 'L'Oréal-UNESCO For Women in Science' fellowship (2022). (PAP)

PAP - Science in Poland,  Agnieszka Libudzka

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