Journal of Marine Science and Engineering (Aug 2024)
Feeding Habits of <i>Scomber japonicus</i> Inferred by Stable Isotope and Fatty Acid Analyses
Abstract
Scomber japonicus is widely distributed off the coast of Japan and in the northwestern Pacific. It is an important target for fisheries. To reveal the differences in diet shifts and niche changes of S. japonicus, we collected samples in the high seas of the northwest Pacific (38°59′ N–43°00′ N, 150°30′ E–161°48′ E) from June to August 2021. We utilized stable isotope and fatty acid analyses to study the differences in body length and sex of S. japonicus. The results showed no significant differences in stable isotope values and fatty acid composition between male and female individuals (p > 0.05). Differences in δ13C and δ15N values among different body length groups were also not significant (p > 0.05). Both δ13C and δ15N values showed a trend of increasing and then decreasing across different body length groups. The niche width of S. japonicus in different body length groups first increased and then decreased, with niche overlap among the groups exceeding 60%. Principal component analysis (PCA) results showed that the main fatty acids in S. japonicus were C14:0, C16:0, C18:0, C16:1n-7, C18:1n-9, C18:3n-6, C20:5n-3, C20:4n-6 and 22:6n-3. Except for C18:0 and C20:4n-6, the content of the other fatty acids showed significant differences among different body length groups (p p p > 0.05). During the growth and development of S. japonicus, the proportion of krill in their diet gradually decreased. Meanwhile, their consumption of zooplankton, diatoms and fish significantly increased. Additionally, S. japonicus also consumed crustaceans, but their intakes of planktonic bacteria and green algae were relatively low. We suggested that there were no significant differences between male and female individuals of S. japonicus. As they grew and developed, the ecological niche and feeding habits of S. japonicus continuously changed.
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