Are there one or two stocks of Scoranza bleak - Alburnus scoranza Bonaparte, 1845 in Lake Skadar (Montenegro)

Abstract

This paper provides the first comprehensive information on the Length-Weight Relationship (LWR) of Scoranza bleak (Alburnus scoranza) from the Lake Skadar. The results of the study showed that LWR was different in young and older individual fish. We concluded that no single regression would adequately describe the length-weight relationship for Scoranza bleak in the winter period. Small fish, up to one year old, have positive allometric growth whereas older and larger, negative. The results of this study show that the animals grow equally in the same pattern in both localities (Raduš and Karuč) which shows that there are no two stocks as it was assumed in the past. The condition factor in young Scoranza bleaks was lower than in the elderly. Condition factor decreased significantly during the winter period in older specimens. Based on this, we conclude that Scoranza bleak during the winter is poorly fed/starved, which causes a decrease in the condition factor.Analysis of the total sample, of any species, cannot show by what rule the population grows, if infrapopulation variability is present, because the studied value will depend on the number of individual subgroups. If no infra-population variability is found, the required parameter for the entire population can be calculated. In order to determine population variability, multiple groups must be singled out. Preferably, the number of stratified samples should be at least 6 so that correlation-regression analysis can be performed. In stratified samples, the number of individuals should be between 30-40, for any parameter, in order to compare their mean values. The results of the study show that 50 individuals are sufficient for accurate determination of LWR (or α and b, α is a constant coefficient and b is the slope of the curve.), when it is determined that there is no intrapopulation variability.