## 1 Introduction  
Fish is a delicious and nutritious food. However, post-mortem fish easily deteriorates because of chemical reactions, endogenous enzymes, and spoilage-causing bacteria [1]. Among these, odor is a critical quality parameter that requires close attention. Temperature control for the quality preservation of fishery products is pivotal, with traditional refrigeration typically maintained at 4 \({}^{\circ}\)C to inhibit microbial growth [2, 3]. Ice storage maintains freshness by inhibiting endogenous enzyme activity in food and by reducing microbial proliferation [4]. Super-chilled (SC) storage involves the partial freezing of water in food, typically cooling it to 1-2 \({}^{\circ}\)C below the initial freezing point. Storing food at SC temperatures offers three distinct advantages: maintaining freshness, retaining high quality, and suppressing the growth of harmful microbes [5, 6]. [PERSON] et al. reported that this method extends the shelf life of fresh cod by 2-3 days compared with traditional refrigeration, which provides a shelf life of 9-13 days [7]. Odor change is one of the most influential factors in degrading fish flesh quality. Some individuals avoid eating fish-based cuisine because of their unpleasant odor. Storage temperature plays an important role in the development of off-odors in seafood by affecting the growth of spoilage-causing bacteria, mainly gram-negative, and their metabolic activities [8]. In addition, volatile organic compounds (VOCs) derived from lipid oxidation are produced in fish muscle during storage, even in the absence of a bacterial contribution [9; 10]. The progress of this lipid oxidation is affected by temperature. Therefore, to maintain the appropriate quality of fish meat, it is necessary to investigate the effect of storage temperature on changes in the volatile components of fish meat during storage. Traditional bacterial colony counting methods may underestimate microbial diversity and spoilage-causing bacteria, owing to their inability to detect unculturable strains. Next-generation sequencing (NGS) enables the precise evaluation of bacterial taxa, including uncultivated microbes or those present in low abundance [11]. In some fish species, the predominant genera associated with flesh spoilage include _Pseudomonas_, _Psychrobacter_, _Photobacterium_, and _Shewanella_[12; 13; 14]. The yellowtail (_Seriola quinqueradiata_) is an important cultured fish species for domestic consumption and export in Japan. This fish species accounts for approximately 48% of the aquaculture production in Japan [15]. In Japanese cuisine, yellowtail ordinary muscle is eaten alone or with dark muscle (DM). DM has a higher concentration of unsaturated lipids and heme proteins, making it more prone to lipid oxidation. As a result, VOCs produced in DM differ from those in OM, leading to distinct odor profiles [9; 10]. In our previous studies, VOC changes in the DM were found to be important for odor deterioration in yellowtail meat compared to OM. Nevertheless, there was no difference in the changes in the bacterial flora between OM and DM during refrigeration [16]. _Pseudomonas_ were found to be predominant in yellowtail meat after spoilage in this study. Therefore, it is important to understand the changes in the VOCs and the bacterial flora of OM as well as DM of this species during storage. In addition, species other than _Pseudomonas_ have been reported to be predominant in fish species other than yellowtail [12], and the predominant bacterial species in spoiled fish meat may differ depending on the storage temperature. Furthermore, many VOCs have been associated with spoilage in fish species [17]. However, the interactions between VOC formation and bacterial shifts during storage at different temperature conditions remain poorly understood. Additionally, limited research has examined how these changes differ between OM and DM, despite their distinct biochemical properties. The DM and OM differed greatly in their characteristics (Table S1).