Comparative assessment of fish diversity indices in protected Vlasina Reservoir and unprotected Gruža Reservoir

Abstract

The species diversity indices, namely the Shannon Index (H), Reciprocal Simpson's Index (1/D), Fisher's Alpha Diversity Index (A), and Pielou's Evenness Index (J), were calculated for both the protected Vlasina Reservoir and the unprotected Gruža Reservoir. A total of 15 fish species were identified in the Vlasina Reservoir during the investigation period from 2003 to 2022, while the Gruža Reservoir revealed 10 fish species within the period from 2013 to 2021. The obtained values of the H, 1/D, and A indices, were not considerably high, sometimes even lower than expected, showing a slight increase in recent years for both reservoirs. In Vlasina Reservoir, the J Index was in a range from 0.2488 to 0.3348, while in Gruža Reservoir it varied from 0.1834 to 0.3832, indicating the low homogeneity in terms of well-balanced fish assemblage structure. Moreover, an increasing trend in recent years has been observed, which favors the dominance of some fish species against the balanced fish structure. Our results provide valuable information about fish diversity and evenness in the investigated areas under high anthropogenic threats, considering the importance of both reservoirs in Serbia.