Influence of selected precipitating agents used for restoration of water reservoirs on the embryogenesis of pike (Esox lucius L.)

Abstract

The aim of the study was to investigate the effect of iron coagulant (IC), aluminum coagulant (AC) and lanthanum modified bentonite (LMB) on the embryogenesis of pike. Physicochemical indicators of the water were determined according to the methods recommended by APHA (1999). The applied precipitating agents (IC, AC, LMB) at appropriate concentrations were sprayed on the surface of water in aquariums with the pike eggs placed on nets. The eggs were observed under a microscope, documenting their development using digital photography NIS Elements Br software. The number of fertilized eggs, embryo survival, and the percentage of malformed larvae were determined. The pike eggs and hatched larvae were recorded and measured. The percentage of fertilized eggs was found to be the highest in the control sample (LW) and in the IC sample (94% and 93.3%, respectively), 85.9% in the AC sample and 81.8% in the LMB sample. The pace of pike embryogenesis in the samples was identical - the embryos in both the control and other samples reached individual stages of embryonic development with an equal number of degree days (DD). The IC group hatched the earliest, and the control sample was the last to hatch (LW). In the control sample, the hatched larvae were the longest and had the lowest percentage of malformed individuals. The control sample also had the highest rate of embryo survival (85.9%), while the lowest was in the LMB sample (68.6%). These results indicate that the application of precipitating measures to improve water quality should not coincide with the periods of fish reproduction.