D. TERZIYSKI1, R. KALCHEV2, L. HADJINIKOLOVA1, K. DOCHIN1 and A. IVANOVA1
1 Institute of Fisheries and Aquaculture – Plovdiv, BG-4003 Plovdiv, Bulgaria
2 Institute of Zoology, Bulgarian Academy of Sciences, BG-1113 Sofia, Bulgaria
TERZIYSKI, D., R. KALCHEV, L. HADJINIKOLOVA, K. DOCHIN and A. IVANOVA, 2010. Variability of chemical characteristics and their relations to environmental and biological variables in two variants of ponds stocking with fish larvae. Bulg. J. Agric. Sci., 16: 341-349
The top-down effect of common carp (Cyprinus carpio L.) and bighead carp (Aristichthys nobilis Rich.) larvae with densities applied in two different proportions on several chemical variables (pH, NO3-N, NH4-N, PO4-P, oxidability by KMnO4, dissolved oxygen) in fish ponds was tested. The first two ponds were stocked with common carp and bighead carp larvae in abundance proportion 3:1 (variant 1), while further two ponds were stocked in 1:3 ratio of the same fish species (variant 2). The experiment lasted 4 months (May to September) and was repeated in two consecutive years (2007, 2008).
The first year experiment was carried out on ponds from two different localities (with two different water sources: surface and underground) equally presented in each stocking variant, while second year experiment took place in one and the same locality but variant No2 was carried out on three instead on two ponds. The first year experiment showed a single statistically significant difference between two stocking variants for oxidability, while the second year experiment revealed significant differences for both multiple comparison of recorded chemical variables and for two single comparisons (pH and dissolved oxygen) in favor of variant No2. However, the underground water proved to be richer in NO3-N, showed higher N P-1 ratio and pH after entering the ponds. In the first year multiple seasonal variations of chemical variables were related to physical while in the second year to biological variables.