# Ecological Characteristics of Large-Bodied Sharks in the East Sea of Korea

## TL;DR

This study explores six large shark species in Korea's East Sea, revealing their feeding habits, age ranges, and the region's role as a key habitat.

## Contribution

The first comprehensive ecological baseline for large-bodied sharks in Korean waters, including age, diet, and habitat use.

## Key findings

- Six large shark species were identified, with shortfin mako, salmon, and blue sharks most common in summer.
- Age analysis showed juveniles in shortfin makos and adults in salmon and blue sharks.
- Diet and stable isotope data revealed species-specific feeding preferences and trophic niche partitioning.

## Abstract

Large sharks are top predators that help maintain balance in marine ecosystems; however, little is known about them in Korean waters. This study provides the first comprehensive overview of large-bodied sharks in the East Sea of Korea. Six species were recorded, with shortfin mako, salmon, and blue sharks most frequently observed during the summer months. Age analysis showed that shortfin makos were mainly juveniles, whereas salmon and blue sharks were generally adults. Overall, diets were predominantly fish, but feeding preferences differed among species. These results indicate that the East Sea serves as an important feeding ground and nursery habitat for some sharks. Overall, this study establishes a baseline for understanding large sharks in the region and helps guide conservation and public safety measures.

Large-bodied sharks are key apex predators in marine ecosystems; however, ecological data from Korean waters are limited. From February to November 2024, 44 individuals from six species were collected. Of these, 24 individuals were analyzed for ecological characteristics: shortfin mako (Isurus oxyrinchus, n = 6), salmon shark (Lamna ditropis, n = 11), blue shark (Prionace glauca, n = 6), and great white shark (Carcharodon carcharias, n = 1). Age and growth parameters were estimated from vertebral band counts using the von Bertalanffy growth model. Diet was assessed via stomach content and DNA metabarcoding, and trophic relationships were examined using stable isotopes. The monthly occurrence peaked in July, with shortfin mako, salmon shark, and blue shark being the most frequently observed species. Estimated ages ranged 8–16, 4–13, and 1–11 years, respectively. The diets were predominantly fish-based, with species-specific prey preferences. Stable isotope data revealed trophic differentiation, suggesting niche partitioning among species. The eastern coastal waters of Korea appear to serve as foraging grounds and potential nursery habitats for large shark species. This is the first comprehensive ecological baseline for these species in Korean waters, which supports future assessments, conservation, and management strategies.