INTERSPECIFIC NUTRITIONAL RELATIONSHIP BETWEEN CLUPEONELLA ENGRAULIFORMIS AND CLUPEONELLA CASPIA IN THE CASPIAN SEA
Vital activity of the Caspian ichthyofauna is mainly determined by aqueous environment with its multiple factors influencing the hydrobionts’ life cycle. It is well known that in the process of evaluating the stocks of commercial fish species it is necessary to take into account supplying them with food. Trophologic studies of mature species of Clupeonella Caspia and Clupeonella Engrauliformis in the Caspian Sea make a basis for a large number of works; however, the research of food preferences of these fish species is scarce. Clupeonella Caspia inhabits the north, middle and south parts of the Caspian Sea above the 60 m isobath. Clupeonella Engrauliformis is widespread in the middle and southern parts of the Caspian Sea above the depths more than 200 m. In the course of evaluating kilka fattening in the Caspian Sea that was continued in 2011 there were estimated nutrition relations of kilka species over the many years, traced the degree of nutritional similarity and registered interspecific relationship between these pelagic fish. The results obtained have been summarized and the whole range of trophic studies has been shown. The monitoring nature of the studies allows to infer the intensive feeding of Clupeonella Caspia and Clupeonella Engrauliformis in the summer of 2011-2014 and in 2016 in the middle part of the Caspian Sea (the study of pelagic fish fatting was not conducted in 2015). The multi-year comparative analysis of Clupeonella Caspia and Clupeonella Engrauliformis nutrition demonstrated the differences of using the dominant foodstuff among planktonic invertebrates. It has been stated that the index of similarity of the food spectrum does not always have a greater degree of coincidence in close relationship of fish in a systematic respect.