Finding of Mating Helmet Crabs, Telmessus cheiragonus (Tilesius, 1815) (Decapoda: Cheiragonidae), in the Northern Sea of Okhotsk

Mating individuals of the helmet crab Telmessus cheiragonus were found during scuba diving in Taui Bay, Sea of Okhotsk, in September 2024. Mating occurred within depths 0.6–10 m and at a water temperature of 8–9°C. The largest crab aggregations were observed at a depth of 2.5–2.8 m in the macrophyte zone. The minimum carapace width in functionally mature males was 84 mm, while in females it was 48 mm. The ratio of females to males found during the study was 1 : 1.8 in general.