A Fish Not Seen for 50 Years Has Returned to the Sea of Azov

The Sea of Azov is currently undergoing a chemical shift that has not been seen in 150 years. Salinity has reached a record 16 parts per thousand (ppt), a threshold that effectively transforms the basin's biological identity. This is not merely a statistical peak but a systemic trigger that alters the competitive balance between indigenous species and migrants from the Black Sea. The central tension lies in the physiological limits of the local fauna. For migratory and semi-migratory fish—such as bream, zander, taran, and dace—the increased salt concentration creates a chemical barrier, making it physically difficult to ascend rivers for spawning. This loss of accessibility to breeding grounds is compounded by the disappearance of relict goby species, as noted by hydrobiologist Tatiana Petrova. While local populations decline, the environment has become hospitable to Black Sea intruders. The appearance of the tub gurnard (sea cock) in the Taganrog Bay—the first sighting in 50 years—and the influx of turbot indicate that the Sea of Azov is biologically merging with its larger neighbor. This shift is further evidenced by the proliferation of rhizostome jellyfish, which thrive in the new salinity levels, turning parts of the water column into a dense gelatinous mass.