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With consumers demanding higher quality in fish products, ecologically farmed fish are increasingly favored due to their quality being close to that of wild fish. However, the differences between the ecologically farmed and wild fish remain largely unclear. In the present study, the wild and ecologically farmed large yellow croakers of the same size were captured simultaneously from the same marine area around Nanji islands (27.479°E, 121.052°N). Then, synchronous tests were conducted to evaluate quality to clarify the key quality parameters that differentiate between the wild and farmed fish. We obtained 49 quality parameters after orthogonal partial least squares discriminant analysis (OPLS-DA) with variable importance in projection (VIP) scores >1 and p < 0.05 using 307 indicators related to 121 length ratios, 4 body color indicators, 5 muscle fiber characteristic indicators, 87 nutrition quality parameters, 40 taste parameters, and 50 volatile compounds. Compared to the farmed fish, the wild fish exhibited a more yellow skin color, higher levels of carotenoids, and a more streamlined conical shape. Changes in histology and ultrastructure of muscle fibers were noted, including increased muscle fiber density and the ratio of fiber area to gap, as well as reduced I band width, observed in the wild fish. The wild fish had high nutritional value of fatty acids and minerals and low nutritional value of amino acids, as reflected by higher levels of C22: 6n3 (DHA), Σn-3 PUFA (polyunsaturated fatty acids), Σn-3/Σn-6 PUFA, Na (sodium), K (potassium), Fe (iron), and Se (selenium), and lower values of ΣMUFA (monosaturated fatty acids), Σn-6 PUFA, TI (thrombogenic index), amino acid and chemistry scores of isoleucine, ΣEAA/ΣTAA (essential amino acid/ total amino acid), and ΣTAA/ΣNEAA (total amino acid/non-essential amino acid) in the muscles of the wild fish. The wild fish muscle showed high levels of hydrolyzed glycine and proline and free methionine, and low levels of free glycine and proline, indicating a propensity for collagen synthesis. Despite significant differences in the contents of fourteen flavor substances of free amino acids, 5′-nucleotides, and volatile compounds, their concentrations were notably below the corresponding threshold and contributed minimally to flavor, suggesting that the wild and farmed fish shared similar flavor characteristics. In summary, this study reveals the quality differences between ecologically farmed and wild large yellow croaker based on on-site synchronous sampling, providing a theoretical foundation for further enhancing the quality of this species. • The quality of ecologically farmed and wild large yellow croaker was compared. • The quality evaluation was based on on-site synchronous sampling. • The farmed fish had high amino acid nutrition and similar flavor characteristics. • Shape, color, lipid and mineral nutrition, and texture needed improvement in farmed fish. • Novel quality enhancement strategies are suggested during ecologically culture. [ABSTRACT FROM AUTHOR]

Relay culture of large yellow croaker from Fujian to Zhejiang is a good model for improved fish quality. However, there is a scarcity of information regarding the comprehensive evaluation of quality alterations following relay culture. In the present study, the large yellow croaker from Ningde (ND) was transferred to net cages in Dongtou (DT), Nanji (NJ), Dongji (DJ) and Dacheng (DC) for continued culture. The 15-month-old fish from ND, DJ, DC, DT, and NJ were sampled on-site for a subsequent comparative study on the morphological characteristics, nutritional quality, and tastes. Results showed that the fish from DJ, DC, DT, and NJ had a lower condition factor (CF) and a higher ratio of body length to height (L/H) than those from ND. The fish from DJ, DC, DT, and NJ, at rates of 77.8%, 91.3%, 95.7%, and 100%, exhibited different geometric morphometrics from those from ND using 10 typical landmarks and Morpho J software. Ralay culture also significantly affected the histology and ultrastructure of muscle fibers, as reflected by an increase in the muscle fiber density and decreases in the ratio of fiber area to gap, I band width, and sarcomere length in the relay culture fish compared to the ND fish. The relay culture fish showed low lipid content and high moisture content. Relay culture also significantly affected the levels of some nutritional composition, including deceases in the levels of hydrolyzed glycine, C16:0, C18:1n9c, C18:2n6c, Σn-6 PUFA (polyunsaturated fatty acids), Fe (iron), Mn (manganese), and Co (cobalt), and increases in the levels of C20:5n3 (EPA, eicosapentaenoic acid), C22:6n3 (DHA, docosahexaenoic acid), C18:0, Σn-3/Σn-6 PUFA, Σn-3 PUFA, Al (aluminum), Se (selenium), Na (sodium), and Ca (calcium). The levels of taste substances such as guanosine monophosphate (GMP) and most flavor amino acids sharply declined after relay culture. However, the ratio of taste activity value (TAV) of ΣDAA to ΣBAA (delicious amino acids/bitter amino acids) in the DT and NJ fish was higher than that in the ND fish. Significant negative relationships between market price and quality parameters were found, including CF, crude lipid, C18:1n9c, C18:2n6c, Σn-6 PUFA, Fe, Mn, and TAV of GMP, whereas there were positive relationships between market price and 4 quality parameters such as L/H, moisture, Σn-3/Σn-6 PUFA, and the ratio of TAC of ΣDAA to ΣBAA. In conclusion, relay culture improved large yellow croaker quality by changes in morphological characteristics, nutritional quality, and tastes, which provides a theoretical basis for quality improvement. • Relay culture improved body shape, nutritional quality, and tastes of fish. • Significant relationships between the market price and quality indicators were observed. • Novel quality enhancement strategies are suggested during relay culture. • Relay culture is a promising model for enhancing the quality of large yellow croaker. [ABSTRACT FROM AUTHOR]

People commonly consume large yellow croaker with skin, yet comprehensive studies on the skin's nutritional value, flavor, and health risks are lacking. The skin from wild fish and those from five main farming areas, nearly representing all fish in the market, were analyzed. The study revealed that the skin of all tested fish exhibited high levels of carotenoids, EPA, DHA, Σn-3/Σn-6 PUFA, Fe, Se, Cu, Zn, and various flavor compounds including free amino acids, 5′-nucleotides, and odor substances, and low levels of atherosclerotic and thrombogenic indices, suggesting health benefits. Notably, the wild fish skin was yellower with high carotenoid accumulation and nutritionally superior in fatty acids but showed a high heavy metal risk. Additionally, this research has, for the first time, elucidated that carotenoid storage in the skin of large yellow croaker depends on lutein esterification with oleic, palmitic, and decanoic acids. In summary, the current study indicates that the skin of farmed fish offers significant nutritional value and favorable flavor profiles, making it safe for consumption. However, while the skin of wild large yellow croaker is more nutritionally advantageous, it also presents a non-negligible risk of heavy metal contamination. • Nutritional and flavor profiles of large yellow croaker skin were firstly studied. • The quality evaluation was based on on-site synchronous sampling. • Carotenoid nature composition was firstly studied in the skin of the species. • Carotenoid storage depended on lutein esterification with specific fatty acids. • Wild fish had higher nutritional values than farmed fish but showed heavy metal risk. [ABSTRACT FROM AUTHOR]