Insights into the circulating microbiome of the Atlantic and Greenland halibut populations: the role of species-specific and environmental factors

Abstract The establishment of long-term microbiome-based monitoring programs is critical for the management and conservation of wild fish populations in response to climate change. In most cases, these studies have been conducted on gut and, to a lesser extent, skin (mucus) microbiomes. Here, we exploited the concept of liquid biopsy to study the circulating bacterial microbiome of two Northern halibut species of economic and ecological importance. Amplification and sequencing of the 16S rRNA gene was achieved using a single drop of blood fixed on FTA™ cards to identify the core blood microbiome of Atlantic and Greenland halibut populations inhabiting the Gulf of St. Lawrence, Canada. We provide evidence that the circulating microbiome DNA (cmDNA) is driven by both species-specific and environmental factors. More specifically, we found that the circulating microbiome signatures are species specific and vary according to sex, size, temperature, condition factor, and geographical localization. Overall, our study provides a novel approach for the detection of dysbiotic signatures and the risk of disease in wild fish populations for fisheries management, most notably in the context of climate change.