## 4 Discussion
For the three matrices, the most important shift in the microbial population occurred between 14 and 28 days, when the growth of different bacterial flora reached their stationary phase. After 28 days, in the SG, Enterobacteriaceae mostly dominated the ecosystem, with an OTU corresponding to the _Serratia/Yersinia_ genera representing 35-47% of the total composition. In trout gravlax stored under VP at 3 and 8 \({}^{\circ}\)C, [PERSON] et al. [15] showed that H\({}_{2}\)S-producing bacteria (which include some Enterobacteriaceae) represented a major part of the spoilage microbial flora. [PERSON] et al. [16] also found _Serratia/Yersinia_ in SG on days 14 and 21 with metabarcoding analysis. Smoke seemed to exert an additional selection pressure during storage as the OTU number was lower in the VP CSS and MAP CSS than in the SG. At the end of the storage, the microbial composition of the MAP CSS was only dominated by LAB, such as _Lactobacillus_ (>90%) and, to a lesser extent, _Leuconostoc_ (4-6%). These results were in accordance with those obtained with the cultural method, with the LAB count being identical to the TVC. In the VP CSS, depending on the biological replicate, _Lactobacillus_ and _Lactococcus_ were also detected in a high proportion (13 to 37%). The VP and MAP of food commodities are known to favor LAB growth [13; 59; 60; 61]. _Lactobacillus_ and _Lactococcus_ were the main LAB genera that were detected in the products. Many species of _Lactobacillus_ (_L. alimentarium_, _L. casei_ subsp. _tolerans_, _L. corymeiformis_, _L. curvatus_, _L. delbrueckii_ subsp. _delbrueckii_, _L. fractiminis_, _L. fuchtenisis_, _L. homohioichi_, _L. malfermentans_, _L. plantarum_, _L. pentosus_, _L. brevis_, _L. sakei_ and _L. santratscensis_) and _Lactococcus_ (mainly _L. piscium_, but also _L. lactis_ and _Lplantarum_) are frequently isolated from seafood products [17; 62; 63; 64]. Although the spoilage potential of LAB in seafood is strain-dependent, some species, such _L. sakei_, _L. fucriminis_ and _L. fuchtenis_, frequently induced off-odor in shrimp, raw salmon and CSS. Other species (_L. alimentarius_, _L. piscium_) generally do not affect the quality [18; 63; 65; 66; 67]. No sign of alteration was found in the MAP CSS, even after 35 days. This may have been due to the absence of such spoilage species. However, the relatively low concentration of LAB (10\({}^{7}\) CFU/g) may also explain this result. In the VP CSS, the _Photobacterium_ relative abundance increased from day 14 to day 28 and was dominant, accounting for 78 to 97% of the microbial composition. _Photobacterium_ is capable of anaerobic respiration via the use of TMA-oxide, which is often present in marine fish, as a final electron acceptor, making this bacterium able to grow under MAP and VP [50]. The final metabolite, namely, the TMA, is strongly malodorant and responsible for \"amine\" off-odors. _Photobacterium_ was also found to be part of the dominant microbial flora of VP CSS [12; 18]. However, caution must be taken with a metabarcoding approach as its detection might be largely overestimated due to the use of the 16S rRNA gene as a target. According to the rrmDB database [68], _Photobacterium_, especially _P. phosphoreum_, which is the main species encountered in seafood, possesses 15 copies of the 16S rRNA gene in its genome, while the average copy number for the bacterial kingdom is only 4.8. The three products' sensory qualities remained acceptable for the whole storage duration. Usually, lightly preserved seafood products are declared spoiled and unfit for consumption after 3 to 4 weeks for fish gravalax [14; 15] and after 5 to 6 weeks for CSS [3; 4; 5; 6; 9; 10], and their final bacterial load can reach 8 to 9 log CFU/g [13]. In our study, the extended shelf-life might be explained by the low TVC count, which never exceeded 7-8 log CFU/g, which was probably related to high salt and smoke concentrations.