Distribution and some biological features of bottom skate Bathyraja bergi in the Russian waters of the Sea of Japan

Abstract

The spatial and depth-related distribution, the size spectra, and the feeding peculiarities have been studied for the bottom skate Bathyraja bergi in the Russian waters of the Sea of Japan for the trawl catches performed in 1986−2015. The species is found at the depths of 38−577 m at the water temperature of 0.3−3.8°C; during the warm season, the fish keep mainly at the shelf, while they keep at the continental slope in the cold period of the year. This species is found nearly everywhere at the preferred depth range, except a part of the Strait of Tartary. The highest population density has been registered in the southwestern Peter the Great Gulf, along the border with the Korean waters. The schools of the bottom skate of the continental slope and the island shallows do not interact with each other. The specimens reach a body length of 129 cm and a body weight of 13.84 kg. The feeding habits indicate that this species is a predator; decapods (59.9%), cephalopods (23.0%), and fish (15.3%) dominate in the food. In spring, average daily ration constitutes 0.9% of the body weight. In the Russian waters of the Sea of Japan, the bottom skate is a common species, however, it is not abundant; the biomass of the population in this area is approximately 1500 tons.