Recognized for its high nutritional value and minimal environmental impact, insect meal (IM) has gradually found its way into fish dietary regimes. However, exceeding 15% inclusion of IM in fish feeds often leads to reduced feed efficiency and decreased growth performance. To address this challenge, the introduction of chitinolytic sporeforming probiotics has previously shown to enhance both feed efficiency and chitin digestibility in European seabass. To comprehend if their effect was due to a modulation of the fish gut microbiota, the supplementation of two chitinolytic sporeforming probiotics closely related to Bacillus licheniformis (Fish isolates 645 (FI645) and 658 (FI658)) to IM diets was assessed using high throughput 16S rRNA gene amplicon sequencing. Overall community composition remained similar, despite the probiotic supplementation. Our findings indicate that the mechanisms by which chitinolytic-probiotics lead to increased feed efficiency and chitin digestibility in European seabass in not by inducing massive changes on the fish gut microbiota nor on the aquaculture system microbial community. Sequencing was performed at the Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna under the project ID JMF-2205-06