One of the main concerns in the salmon industry is gill disease, which can significantly affect the production of Atlantic salmon (Salmo salar).
A new study conducted by the University of St Andrews, the University of Alaska Fairbanks, the Scottish Association for Marine Science, the University of Aberdeen, and the Sitka Sound Science Center is shedding light on the role of resident microbes, or the microbiota, in fish health. This study, published in a recent issue of BMC Veterinary Research, investigated the link between the gill microbiome and diseases in farmed Atlantic salmon.
What is the resident microbiome?
Imagine a tiny universe living in your fish’s gills. This microscopic community, called the microbiome, is composed of various bacteria, some beneficial and others potentially harmful. Understanding how this community functions is key to preventing diseases.
Understanding the Role of Microbes in Fish Diseases
Fish gills, as the main interface between a fish and its environment, are susceptible to a variety of diseases. These diseases can significantly impact the aquaculture industry, especially in Atlantic salmon farming. While pathogens like bacteria are often associated with gill diseases, emerging research suggests that the fish’s own microbiome (the community of microbes living on their gills) plays a crucial role in health and disease.
A Complex Ecosystem
The gill microbiome is influenced by a multitude of factors, including environmental conditions such as water temperature and salinity, as well as the fish’s immune system. These factors can shape the composition of the microbial community, determining whether it is beneficial or harmful to the fish.
Diseases and the Microbiome
Studies have shown that disruptions to the gill microbiome can lead to increased susceptibility to diseases. For example, parasites such as sea lice can disrupt the microbial balance, making fish more vulnerable to infections. Additionally, diseases like amoebic gill disease (AGD) have been linked to changes in the gill microbiome.
Identifying Health Indicators
By analyzing the microbial community in fish gills, scientists can identify early signs of disease. The presence of certain microbes or changes in their abundance could serve as indicators of an unhealthy gill microbiome.
Dynamic Communities: Microbes in Flux
The researchers used advanced sequencing techniques to analyze the microbial communities present in salmon gills over the course of a single production cycle. This revealed that the composition of these communities is constantly changing, influenced by various factors such as environmental conditions and the health of the fish.
Friendly Microbes vs. Pathogens
The good news is that some microbes seem to play a protective role. Specific types of bacteria, such as those belonging to the genus Shewanella and the family Procabacteriaceae, were found in greater abundance in healthy salmon gills. These “friendly” microbes might help keep harmful pathogens at bay.
On the other hand, other microbes were more prevalent in fish with damaged gills. Among them were species like Candidatus, Branchiomonas, and Rubritalea. While more research is needed to understand their exact role, their increased presence could be a sign of gill health issues.
Decoding the Puzzle: More Research Needed
While this study provides valuable insights, it also highlights the complexity of the relationship between the microbiome and gill disease. The research suggests that overall changes in microbial diversity were not directly linked to gill health. Moreover, identifying specific causes of gill damage, such as infectious agents, proved challenging due to the study’s design.
Implications for the Salmon Industry
These findings open new avenues for research in this area. By conducting more frequent sampling and manipulating the gill microbiome in controlled conditions, scientists can better understand how different microbial communities affect fish health.
On the other hand, understanding the role of the gill microbiome in fish health opens new possibilities for disease prevention and treatment. Manipulating the microbiome, perhaps through probiotics or other interventions, could potentially help maintain a healthy environment for fish and reduce disease risk.
Conclusion
This study represents a significant advance in understanding the complex interaction between the microbiome, environmental factors, and fish health. By identifying potential microbial markers of gill health, researchers can pave the way for the development of new strategies to prevent and control gill diseases in farmed Atlantic salmon. This ultimately contributes to a more sustainable and successful aquaculture industry.
The study was funded by BBSRC through the EASTBIO program, along with a grant from the Marine Alliance of Science and Technology Scotland (MASTs).
Contact
Morag Clinton
Scottish Oceans Institute, University of St Andrews, St Andrews, UK
Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, AK, USA
Sitka Sound Science Center, Alaska, Sitka, USA
Email: mclinton@sitkascience.org
Reference (open access)
Clinton, M., Wyness, A.J., Martin, S.A.M. et al. Association of microbial community structure with gill disease in marine-stage farmed Atlantic salmon (Salmo salar); a yearlong study. BMC Vet Res 20, 340 (2024). https://doi.org/10.1186/s12917-024-04125-5
