Abstract

The big-belly seahorse, Hippocampus abdominalis has been known to be limitedly

distributed in the temperate seas of Australia and New Zealand. However, a single individual (197.14 mm in total length) of big-belly seahorse was collected using a fish trap from Pohang, Gyeongsangbuk-do, Republic of Korea on August 5, 2023. This is the first record of occurrence of the big-belly seahorse in the wild of Korea. We compared our single wild-captured individual with two aquarium-reared big-belly seahorse individuals from Jeju Island, using morphological and molecular methods. The big-belly seahorse specimens were well-matched with our wild-captured individual in terms of the numbers of dorsal fin rays (25–26), trunk rings (12–13), and tail rings (44–45). In addition, molecular analysis based on 609 bp of the mtDNA COI sequences showed a perfect match of 99.8–100%. Our wild-captured individual is likely to be escaped from the aquarium in Jeju Island and transported to Pohang by oceanic current. This record is noteworthy in providing potential of survival of the big-belly seahorse in the wild of Korea, suggesting that monitoring of the population of big-belly seahorses in the wild of Korea is necessary.