THE STUDY OF SOME MORPHOLOGICAL CHARACTERS AT THE ARISTICHTHYS NOBILIS SPECIES IN DIFFERENT STAGES OF DEVELOPMENT

Gabriela Dumitru, Elena Ciornea, Silvia Vasile

Abstract
The work aimed to the study of some bodily variables at the three summer-old, respectively, four summer-old Aristichthys nobilis (bighead carp) representatives, derived from a systematic arrangement. For that, were used a number of a 100 individuals for each age in part, determining a series of morphological characters, such as: the body's total and standard length, the head's length, the height, the body's circumference and weight. Thus, for each pair of analyzed variable (the body's standard length in regard with the head's length, the body's total length and weight, respectively, the height in regard with the body's circumference), was calculated the Pearson index of parametric correlation, being then tested the signification of this one. The values of t calculated were compared with those of t critic (a=0.05, n-2) = 1.985, establishing the null hypothesis (that doesn't exist correlation) and alternatives (that exists correlation), and on the basis of the comparing of t calculated value with critical t was accepted one of the two hypothesis. Hereinafter was traced the straight line of regression and the regression equation of the straight line, then was determined the coefficient of regression, that is in what measure a variable determines the increasing of the other variable as well as the determination coefficient (R^{2}) which denotes how percent from the values took of the dependent variable are determined of the independent one and reciprocal. The statistical analysis denotes the existence of some positive correlations between all the pairs of morphological characters studied, with the mention that at the three summer-old bighead carp the correlation between the body's standard and total length resulted to be the most significantly statistic (r=0.966), while at the four summer-old representatives on the first place is the correlation between the body's circumference and height (r=0.996).