Population Structure of Alien Snow Crabs ( Chionoecetes opilio ) in the Kara Sea (Trawl and Video Sampling)

The paper presents the results from a study of the population structure of alien snow crabs Chionoecetes opilio in the western Kara Sea near the Kara Strait using two methods: Sigsby trawling and video surveillance. The towed unmanned underwater vehicle Videomodule was used to estimate the population density of crabs: 0.55 ind/m 2 in 2016, and 0.17 and 0.09 ind/m 2 in 2017. No differences were revealed when comparing the size structure of the crab population based on the two methods. An exception is possible underestimation of younglings with a carapace width <20 mm when using the Videomodule. The minimum observed carapace size was ~10 mm, and the maximum, 127 mm. Both methods revealed the presence of all stages of crab growth, which indicates successful survival and growth of this crab in the western Kara Sea. An adequate assessment of the development of invasion of alien C. opilio in the Kara Sea requires annual video observations in the regions representing characteristic biotopes at different distances from the Kara Strait.