Agnieszka Rybczyk

The application of ceramic membranes for treating effluent water from closed-circuit fish farming

Abstract The aim of the study was to analyze and assess the possibility of using a two-stage filtration system with ceramic membranes: a 3-tube module with 1.0 kDa cut-off (1st stage) and a one-tube module with 0.45 kDa cut-off (2nd stage) for treating effluent water from a juvenile African catfish aquaculture. The study revealed that during the 1st filtration stage of the effluent water, the highest degrees of retention were obtained with respect to: suspended solids SS (rejection coefficient RI=100%), turbidity (RI=99.40%), total iron (RI=89.20%), BOD5 (RI=76.0%), nitrite nitrogen (RI=62.30%), and CODCr (RI=41.74%). The 2nd filtration stage resulted in a lower reduction degree of the tested indicators in comparison to the 1st filtration stage. At the 2nd stage, the highest values of the rejection coefficient were noted in for the total iron content (RIV=100%), CODCr (RIV=59.52%; RV=64.28%, RVI=63.49%) and turbidity (RIV and RV = 45.0%, RVI=50.0%). The obtained results indicate that ceramic membranes (with 1.0 and 0.45 kDa cut-offs) may be used in recirculation aquaculture systems as one of the stages of effluent water treatment.

Seasonal Changes in Condition Factor and Weight-Length Relationship of Invasive Carassius gibelio (Bloch, 1782) from Leszczynskie Lakeland, Poland

Samples of invasive cyprinid fish, the Prussian carp (Carassius gibelio), were collected by fyke nets in Leszczynskie Lakeland (Poland) during the summer and autumn, 2010, and during the spring, 2011. All captured fish were females. For each fish, the total weight () and the standard length () were measured and Fulton’s condition factor was computed. Graphical investigation and the Mann-Whitney-Wilcoxon test showed statistically significant location shift of the distribution from summer to autumn (upward) and from autumn to spring (downward). Relationship between total weight and standard length was described with the mean growth curve . Seasonal parameters ( and ) were estimated with a nonlinear regression approach, that is, numerical optimization methods. Growth was allometric in summer and autumn and isometric in spring. The differences between summer and autumn growth curves and between autumn and spring growth curves were statistically significant. The seasonality exhibited by the condition factor and the growth curve may be due to different spawning, breeding, and feeding activity in the different seasons and to variable environmental conditions.

Specifying the relationship between key stages of pike (Esox lucius L.) embryogenesis and coagulants used in lake recultivation

Abstract The study focused on the effect of iron and aluminium coagulants (PIX®113, PAX®18) commonly used for purification of open waters on key stages of embryonic development of pike (Esox lucius L.). Fertilized pike roe was incubated in lake water and in water with the admixture of coagulants, applied in the concentration of 50.0 mg dm-3 at selected stages of embryogenesis: blastopore closure, inoculation, and the hatching of larvae. In the course of the experiment, live embryos were observed and total lengths of the larvae were measured. Simultaneously, selected hydrochemical indicators were gauged. It was discovered that coagulants had the strongest effect at the first stage of embryogenesis (the end of the process of gastrulation). At that stage the survival rate of embryos was the lowest (73.5- 75.0%) and the percentage of deformities in the hatched larvae was the highest (9.7-10.0%).