Analysis of morphological changeability of sardelle (clupeonella cultriventris, nordmann, 1840) of Dnipro-Bugh mouth system

Abstract

The regulation of the natural channel of Dnipro, which beginning took place in the first half of fifties of previous century, caused the cardinal worsening of hydrobiocenosis condition of Dnipro-Bugh mouth system. The transformational processes that last till today are attended with the changes of main biological characteristics of ichthyocenosis, where sardelle - Clupeonella cultriventris (Nordmann, 1840) was always the most numerous representative of herring. In this connection the aim of research was formed – to analyze the main morphological features of sardelle from Dnipro-Bugh mouth system under modern conditions, to compare them with the literary data of previous century and to trace the possible changes of body proportions in time. At that the certain attention was paid to detection of sex dimorphism in herd. For attaining the set aim, the correspondent volume of scientific-research works was carried out using the methods and instructions, generally recognized in ichthyological practice. The morphological changeability was determined by Student t-criterion (t d ) taking into account the actual volume of sampling (n)and significance level (р<0,05). The analysis of meristic signs of sardelle demonstrated that the fin formulas are the following: D – ІІІ-ІV (М=3,46±0,06) 7-12 (М=9,67±0,18); A – ІІІ-ІV (М=3,44±0,06) 10-18 (М=13,06±0,22); P - 11-17 (М=13,17±0,16); V – 6-11 (М=8,60±0,15); С ІІ (IV) (М=2,09±0,05) 19-26 (М=21,93±0,16), and the number of abdominal spinules is 24—28 (М=25,94±0,16). It was established, that the most essential changes of body proportions in sardelle in the process of Dnipro channel transformation take place by the indices of anteventral distance (t d =10,06; р<0,05) and breast fins length(t d =10,99; р<0,05). The existence of sex dimorphism in herd was proved. Among 20 analyzed plastic signs the reliable difference was revealed by 12 indices, but it was more significant by the most body height, antepectral distance and abdominal fins length – t d =4,5-6,8 (р<0,05)