VARIABILITY OF BIOLOGICAL CHARACTERISTICS AND THEIR RELATIONS TO ENVIRONMENTAL VARIABLES IN FISH PONDS STOCKED WITH CARP FISH LARVAE IN TWO DIFFERENT PROPORTIONS
2010
Terzijski, D., Institute of Fisheries and Aquaculture, Plovdiv (Bulgaria) | Kalchev, R., Bulgarian Academy of Sciences, Sofia (Bulgaria) | Dochin, K., Institute of Fisheries and Aquaculture, Plovdiv (Bulgaria) | Piskov, I., Institute of Fisheries and Aquaculture, Plovdiv (Bulgaria) | Kalcheva, H., Bulgarian Academy of Sciences, Sofia (Bulgaria) | Pehlivanov, L., Central Laboratory of General Ecology, BAS, Sofia (Bulgaria)
The top-down effect of densities of common carp - Cyprinus carpio L. and bighead carp - Aristichthys nobilis Rich. larvae applied in proportions 3:1 and 1:3 on biological fish pond characteristics like plankton primary production, respiration, abundances of bacterio, phyto and zooplankton, chlorophyll etc. was tested. The experiment lasted 4 months - May to September, was repeated in two consecutive years - 2007, 2008 included four ponds in year 2007 from two different localities and five ponds in 2008 from one and the same locality. The measured biological variables showed statistically significant differences between means of localities, years and stocking variants. The sources of variations between localities and years have their ground in objective circumstances accompanying the experiment implementation but could not override the top-down effect of fish stocking variants. The variant 1 3:1 common carp: bighead carp densities which proved to be more effective was distinguished by higher phytoplankton and lower zooplankton abundances. Its primary production and respiration were also lower than in variant 2 1:3 densities of common carp: bighead carp.
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