First Capture of the Deep-Sea Careproctus bathycoetus (Liparidae) a Century After the Fish Was Described (North Pacific)—Revised Diagnosis and Notes on Ecology

The deep-sea snailfish Careproctus bathycoetus Gilbert et Burke, 1912 was described a century ago from a single specimen caught at a depth of 3292 m in the Kuril Basin (southern Sea of Okhotsk, western North Pacific). Until now, it was known from the holotype only. Therefore, the capture of another specimen is of great interest and provides new data on the morphology and ecology of the species. The second known specimen was collected by the international expedition “SohoBio” (2015) at a depth of 3305 m in the Kuril Basin near the type locality. This study provides a description of a rare fish, which allows us to improve the diagnosis of the species. Differences from other deep-sea snailfishes from the North Pacific Ocean are also given. At a depth of 3292–3305 m, the species lives in extreme conditions: complete darkness, temperature at about 1.9 °C, water pressure about 3300 ton/m2, low oxygen concentration, and low biomass of prey. Related Careproctus species can most likely be found in the abyssal depths of the neighboring Kuril–Kamchatka Trench.