IMPACT OF ENVIRONMENT FACTORS ON THE FORMATION OF CASPIAN ROACH (<i>RUTILUS RUTILUS CASPICUS</i>) COMMERCIAL CATCHES IN THE VOLGA-CASPIAN AND THE NORTH-CASPIAN FISHERY SUBAREAS
The article presents analyzes of the influence of long-term see breathing on roach catches. There were studied relations of these indicators within 1959-1976 (low sea-level), 1977-1994 (sea water rise from the minimum to maximum level), 1995-2016 (maximum sea-level falling to modern range). The analysis of longstanding dynamics of roach catches showed the relation with the sea-level fluctuations, under the influence of which bio-productivity of the Caspian Sea is forming. For analysis of the influence of environment conditions on roach catches there was taken the time period of 1975-1988. The results showed the inverse relationship, whereby catches decreased with the increase of flooding. This could happen due to high volumes of water entering the river Delta and preventing from catching fish (depths are increasing, fishing grounds are flooded and fishing ceases). The study shows that the major factors influencing the conditions of the roach fishing are the temperature regime of watercourses in the spring period and the terms of the flooding. In the years of early warming up the water roach came earlier to fishing areas, which created more favorable conditions for fishing. Under the late warming up of the water roach mass run shifted to later periods, when, according to the Rules of the fishery, it is prohibited to use fine-mashed seines. When the terms of the water warming-up to spawning temperatures coincided with the terms of the flooding, roach entered spawning grounds and didn’t stay long in the river, thus its concentrations in the fishing zones took a comparatively short time.