Assessment of ecological conditions for growing the market-size fish in the Kantivka fattening pond (Khmelnychchyna, Ukraine)

Abstract

Abiotic (water quality) and biotic (Phyto-, zooplankton and benthos) factors in the Kantivka fattening pond the Khmelnitskrybhosp Private Joint-Stock Company were studied during the vegetation seasons in 2020. The aquaculture objects in the pond are cyprinid fish species (carp, grass carp, silver carp, pike). The ecological conditions of the pond were evaluated as good enough for the fish fattening purpose. The critical water quality parameters were following traditional values accepted for fish farming in Ukraine. The taxonomic composition of plankton and benthos was represented by widespread and Ubiquiti species mainly. The 124 species and intraspecies taxa of microalgae and the 34 species of zooplankton were identified in the Kantivka fattening pond. The mean abundance and biomass for the phytoplankton were 183.8 million cells/dm3 and 35.61 mg/dm3, respectively; for zooplankton, those were as 336600 ind/m3 and 14.83 g/m3, and for zoobenthos, those values were as 309.6 ind/m2, and biomass as 5.84 g/m2. Such parameters of natural forage base correspond to the optimal values for natural fish food according to fish farming standards in Ukraine. In the late summer, the free-living copepod stages and mature adult females of the parasitic copepod crustacean Ergasilus sieboldi Nordmann were registered in plankton. This copepod causes the invasion of fish diseases like infection and destruction of gill arches, which leads to a severe disturbance in fish respiration, emaciation, delaying in growth, and the potential death of commercial fish even. The development of natural fish food in the Kantivka fattening pond is shown an intensive level of biomass and abundance of phytoplankton, zooplankton, and zoobenthos. It is considered sufficient to meet the natural nutritional needs (in combination with artificial feeding) for older age groups of the cultivated cyprinid fish species.