Abstrak
Hammerhead shark is a species of shark with a distinctive hammer-like head shape and it is known as a top predator in the marine ecosystem. Its existence is important in maintaining the balance of the food chain, but its population is threatened by excessive exploitation. The purpose of this study was to identify the types and molecular characteristics of hammerhead sharks (Sphyrna sp.) from the waters of Tanah Kuning, Bulungan Regency, North Kalimantan, using morphological and molecular approaches through the DNA barcoding method. The study was conducted from December 2024 to March 2025 through a purposive sampling method, by taking five hammerhead shark specimens using a trawl. Identification was carried out through two approaches: (1) morphological analysis including morphometric including total length, head length, and fin shape; and (2) molecular analysis through the stages of DNA extraction, purity measurement, and mitochondrial COI gene amplification with PCR, electrophoresis, and DNA sequencing. Genetic validation was carried out using BLAST analysis and genetic distance calculations using the Tamura 3-Parameter model. The results of morphological identification showed that all samples had the characteristics of the Sphyrna lewini species. Molecular validation through BLAST showed a similarity level of 99.54-100% with GenBank data for Sphyrna lewini, and genetic distance analysis indicated a very close relationship between individuals. This study proved that DNA barcoding was effective for identifying hammerhead shark species and had the potential to support conservation and sustainable management of shark resources in Tanah Kuning waters.