Shifting of the spring migration period of the porpoises (<i>Phocoena phocoena relicta</i>) in the Kerch Strait and in the North-Western Black Sea in 2011-2012
Coastal and vessel observations and record of cetaceans, stranded on the shore in the north-eastern part of the Black Sea and in the Kerch Strait, were conducted in spring 2011 and 2012. It was found out that the terms of mass migration of the Azov porpoise herd to the Azov Sea through the Kerch Strait with a peak in the second decade of April are significantly later than usual ones. Afterwards, occurence of new porpoise aggregations was registered in the studied area, which can be related to the migration of the Crimean-Caucasian herd, as well as subsequent mass mortality of certain specimens from the herd. The hypotheses on the relationships of spring relocation of porpoise herds with migrations of different fish species are precised on the basis of correlations with dynamics of sea surface temperature.