Changes in the abundance and terms of presence in the plankton of the red king crab larvae within the Ura bay (West Murman) in 2011-2016

The distribution and abundance of larvae of the red king crab have been studied in the eastern part of the Ura Bay as part of the Motovskoy Bay (the Barents Sea) during 2011-2016. The larvae of the red king crab in the samples collected here have been recorded from February to June. The highest concentrations of larvae have been recorded in the middle of the eastern part of the Ura bay near the Mogilny island. The highest occurrence of larvae has been observed in mid-water column, mainly on the depth 25 m. The first stage larvae have been mainly occurred in the plankton from February to the end of April. In 2013 the survival rate of larvae of the red king crab was significantly higher than in the other observed years. The maximum abundance of larvae was recorded in March 2014 in the middle of the Eastern strait of the Ura Bay in the local coastal water circulation. The occurrence of larvae into plankton in 2014 began earlier more than a month as in previous years. It was the main reason of larvae early development. In the spring of 2015 relatively low number of larvae and a delay in their development were observed. The highest average larvae abundance and early occurrence in the plankton were recorded in 2014 and 2016. In general, the abundance of pelagic red king crab larvae in the observed period has been comparable to the minimum values recorded in the 90s of the previous century. For the analyzed area of the coastal waters of Murman, the observed dynamics of occurrence and development of the larvae of the red king crab may be caused by more unfavorable for early stages of the species abiotic conditions usual for shallow-water bays of the Murman coast.