Kerch Branch “YugNIRO” of the Sea of Azov Research Fisheries Institute (the FSBSI “AzNIIRKH”), Kerch
UDK 551.579: 574.52 (262.54)
Fish kill events are most commonly recorded in the bays of the northern coastal area of the Sea of Azov, especially in Belosaray Bay, where relatively salt-free waters of Taganrog Bay and more saline waters of the sea itself and high density gradients of water layers develop.
In this article, the data on temperature and salinity of the water surface layer, vertical thermohaline stability of the waters, the magnitude of fish death during fish kill processes in the Belosaray Bay area, as well as on the wind conditions in the northern area of the Sea of Azov are analyzed for the summer seasons of 1989-2016.
The source material for the study of interannual variability of aforementioned hydrological characteristics in the Bay area is the data, collected in the course of annual expedition trips, carried out by AzNIIRKH in this area during summer seasons (July-August) of 1989-2016. Summer wind conditions in this period were assessed for the northern coastal area of the Sea of Azov by average monthly wind velocity in Henichesk in July.
As a result of comparative analysis it is shown, that in 1989-2008 the main factors, contributing to development of conditions, enabling fish kill events and considerable fish death (up to 630 tons), were high values of water temperature and low wind activity. In some years (2002, 2006, 2012), despite high water temperature, fish kill events did not occur due to wind activity.
Long-term decrease in the recorded magnitude of fish kill events (down to 51 tons) during the summer seasons of 2009-2012, as well as their absence in 2013-2016 at stable high summer water temperature are due to drastic unidirectional increase of surface layer salinity, and decrease of water stability and stratification.
Keywords: temperature, salinity, stability, the Belosaray Bay, fish kill event, fish death.
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