T.N. Gerasimova, A.P. Sadchikov
The environmental conditions in a pond deteriorated under the effect of high organic load: water transparency decreased, a large amount of suspension appeared, oxygen deficiency was recorded. The fish in the pond were of large size; therefore, there trophic effect on zooplankton was low. This contributed to the development of a large-size representative of filtering zooplankton Daphnia longispina. Phytoplankton biomass was low with the predominance of euglena, green, and yellowgreen algae. The main food components for D. longispina were the products of ichthyofauna exchange products, i.e., fine detritus, bacteria, and suspended matter. A characteristic of the optimal conditions for D. longispina is its high abundance (385 spec./L), biomass (12 mg/L), fertility, and a wide dimensional spectrum (0,5…2,0 mm), as well as the lack of efi ppial females in the population. At a high concentration of detritus and bacteria in the top layers of the pond, water clarifi cation takes place due to the high filtration activity of daphnia.
Keywords: fishery pond, detritus, fish, water transparency, Daphnia longispina, zooplankton, phytoplankton, green algae, euglena algae.
DOI: 10.25791/esip.2.2022.1285
Pp. 32-37. |
