Trophic ecology of largehead hairtail Trichiurus japonicus in the South Sea of Korea revealed by stable isotope and stomach content analyses

Abstract

Largehead hairtail (Trichiurus japonicus) is one of the most commercially important fishes in the western North Pacific. To identify the dietary changes across ontogeny and seasons, we investigated its stomach contents and stable isotope signatures (δ13C and δ15N) in the South Sea of Korea. The index of relative importance revealed that the dietary composition of largehead hairtail consisted mainly of Pisces (1.6%–84.8%) and Euphausiacea (3.0%–93.0%). However, the proportions of dietary items differed by season and anal length (ALs), suggesting a trophic adaptability response to seasonal food availability and size-related trophic variation, respectively. Our isotopic results showed that the largehead hairtail is placed intermediately between pelagic and benthic fishes and was more 13C and 15N-depleted than other carnivorous fishes, suggesting a high consumption of pelagic species. Similarly, seasonal variations were observed in the δ13C and δ15N values of the largehead hairtails (PERMANOVA, p= 0.001). Interestingly, their δ13C values in spring decreased significantly with ALs (r2 = 0.594, p< 0.001), suggesting an ontogenetic change due to the increased proportion of Euphausiacea to the nutrition of largehead individuals during this specific season. Based on a combination of stomach contents and stable isotope signatures, overall results provide new insights into the feeding characteristics of the largehead hairtail, which improves our understanding of its trophic ecology depending on season and body size.

Trophic structure of fish assemblages in two offshore islands (Ulleungdo and Dokdo) of Korea revealed using stable isotope analysis

“…In the present study, the d 13 C and d 15 N values for SPOM at all the sampling sites were certainly within previously reported isotopic ranges (-24 to -18‰ for d 13 C and 2-10‰ for d 15 N) of general marine phytoplankton and SPOM in coastal waters of the eastern Korean peninsula and other temperate regions (Fry and Sherr, 1984;Park et al, 2020a;Shin et al, 2022). These results indicate that organic matter derived from phytoplankton may be the greatest source of the SPOM pool on both the mainland and island coasts.…”

“…In our study, the differences in the seasonal tendencies of TA and SEAc of fish assemblages between the mainland and island coasts likely reflect the regional isotopic variation in the different prey-consumer relationships due to differing environmental conditions and food availability, as mentioned above (Cherel et al, 2007). Some studies have reported that spatial differences in isotopic niche variability occur due to the alteration of basal resources for fish consumers and their trophic relationships within the community under different environmental conditions (Kingsbury et al, 2020;Shin et al, 2022;Park et al, 2023). In addition, spatial environmental differences related to various physicochemical and biological factors can change fish components within a community, which may lead to regional distinctions in TA and SEAc (Krumsick and Fisher, 2019;Wang et al, 2021).…”