Farmed carp to be healthier

• Scientists are looking for ways to reduce the use of antibiotics in fish farms
• Professor Szyda's project is to last four years and will be carried out together with ichthyologists from the Polish Academy of Sciences

Carp constitutes 80 percent of fish in open waters in Poland. Around 200 000 tonnes of this fish are caught worldwide every year. In Poland, carp accounts for practically half of all freshwater fish caught. This fish is most popular on the menu of Poles at Christmas, but the process of rearing carp takes several years, requires a lot of effort and commitment, careful selection of feed, water oxygenation in ponds, etc.

Microbiome instead of antibiotics?

Scientists, and therefore fish farmers, have recently become interested in using microorganisms to improve water quality, inhibit pathogens and stimulate fish growth. The key is probiotics, which effects on organisms are only just being understood and, in the case of aquaculture, can be an effective way to inhibit or reduce the amount of antibiotics added to farms to protect fish from infection.

– The concept of using probiotic products in fish farms was developed by Japanese scientist Dr Teruo Higa, who proposed a consortium of beneficial and naturally occurring lactic acid bacteria, phototrophic bacteria, actinomycetes, yeasts and fermenting fungi. In total, there are over 80 species of microorganisms that are able to restore a healthy ecosystem in soil and water – says Prof. Joanna Szyda from the Department of Genetics, adding that so far little time and research has been devoted to understanding the impact of probiotic supplementation in farmed carp.

– Especially when these microorganisms are introduced directly into the rearing pond as a mixture of different microorganisms and not into the experimental tank as a specific bacterial species. As part of our project, we will analyse the effect of probiotic supplementation of water and fish food on the microbiome of their gastrointestinal tract – explains Prof. Szyda.

A four-year project

The project is planned for four years and includes the use of bioinformatic methods to model changes in the water microbiome over time, the pond sediment microbiome (also over time) and the correlation between these two microbial communities, taking into account the production cycle of farmed carp.

– There will, of course, be more analyses, as we will also study the microbiomes in the gut of fish reared under different conditions and in water with or without different supplements. We assumed that the information gained would provide a better understanding of changes in the diversity of the microbiome, both in terms of bacterial numbers and abundance. And this will allow us to answer questions about whether and how the fish gut microbiome is dependent on the environment in which they live – stresses Prof. Joanna Szyda.

Carp live in the basins of the Black, Caspian and Aral seas, but farmed varieties are widespread both in farming and in open water throughout almost the entire world. The earliest they were domesticated in China (5th century BC), and Pliny the Elder (23-74 BC) wrote about them in his work "The Natural History". In Europe, it was the first fish to be bred in artificial ponds set up at monasteries. It was thanks to carp that from the 7th to the 12th century there was a rapid development of fishing in the monastic estates of Belgium, France, Germany and the Balkans. They were brought to Poland – to Silesia – by the Cistercians between the 12th and 13th centuries, probably from Czech or Moravian carp farms.

Professor Szyda will carry out the research in cooperation with Dr. Łukasz Napora-Rutkowski and the Department of Ichtiopatology and Fishery Management of the Polish Academy of Sciences in Gołysz near Cieszyn. The centre has 17 domestic and foreign genetic lines of Carp Cyprinus Carpio with a high degree of inbreeding, a number of heterozygous crosses, as well as maternal stock of other fish species. The National Science Centre granted PLN 1,184,760 of funding for this project.