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Simple Summary: The aim of this study was to provide a detailed characterization of the reproductive strategy, embryonic development, and larval development of three fish species from the genus Cichlasoma: the green terror (Andinoacara rivulatus), the red discus (Symphysodon discus), and the jaguar cichlid (Parachromis managuensis). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. Developing eggs were observed from fertilization to larval hatching, up to the complete absorption of the yolk sac. The results of the study will contribute to the development of reproductive biotechnology for the studied fish, enabling effective and easy breeding of these fish under controlled conditions. This will not only meet the demand for these species in the aquarium trade but also protect them in their natural habitat by discontinuing fishing activities. The purpose of this study was to characterize in detail the reproductive strategy, course of embryogenesis, and development of larvae in three species of fishes of the genus Cichlasoma: the green terror (Andinoacara rivulatus), the red discus (Symphysodon discus), and the jaguar cichlid (Parachromis managuensis). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. The developing eggs were observed under a microscope (Carl Zeiss Stereo Discovery. V12 and Nikon 2000SE software (NIS-Elements F 4.30.01 64-bit) from fertilization to larval hatching until complete yolk-sac resorption. The largest average number of eggs per female was found in the jaguar cichlid ( x ¯ = 2991 eggs), a smaller average number of eggs was shown in the green terror ( x ¯ = 922 eggs), and the red discus showed the smallest average number of eggs ( x ¯ = 300 eggs). There were significant differences in the sizes of the eggs of the studied species: jaguar cichlid eggs were the smallest (1.060 ± 0.05 mm3), red discus eggs were larger (1.070 ± 0.07 mm3), and green terror eggs were the largest (1.365 ± 0.16 mm3). The embryogenesis time in the red discus was 2132 °H (82 Hpf), in the green terror it was 2158 °H (83 Hpf), and the longest in the jaguar cichlid was 2470 °H (87 Hpf). At the end of embryogenesis, the average size of the larvae after hatching was measured (red discus x ¯ = 4.346 mm, green terror x ¯ = 5.203 mm, and jaguar cichlid x ¯ = 5.301 mm) and the time of yolk-sac resorption from the moment of hatching to the transition from endogenous to exogenous feeding was determined (jaguar cichlid 5 days, green terror 6 days, and red discus 3 days). The results of this study may contribute to the development of reproductive biotechnology for the studied fishes that could be used in aquaculture and, thus, help protect them in their natural habitats. [ABSTRACT FROM AUTHOR]

River pollution resulting from unregulated and improper water sewage management is a global issue of concern. The discharge of inadequately treated sewage into rivers and the sudden release of excessive quantities during heavy rainfall can result in significant fish mortality. This phenomenon has been observed repeatedly in the case of the Sąpólna River, NW Poland. Consequently, a decision was made to monitor the water quality at two key locations: the drainage channel that feeds into the river and downstream of the channel. Seventeen water quality indicators were measured, including temperature, pH, conductivity, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD5), chemical oxygen demand (CODCr), total organic carbon (TOC), alkalinity, total hardness, total reactive phosphorus (TRP), total phosphorus (TP), nitrite-nitrogen (NO2−-N), nitrate-nitrogen (NO3−-N), total ammonia nitrogen (NH4-N), total organic nitrogen (TON), and total nitrogen (TN). It was determined that, at the location farthest from the drainage channel, water quality still falls short of meeting the specified standards. The primary factors leading to the degradation of water quality at this point were TSS, TRP, NO2−-N, and TN. It was concluded that the primary localized source of water pollution in the studied section of the Sąpólna River is the discharge from sewage treatment plants in Nowogard. Consequently, actions should be taken to address sewage quality and reduce discharge quantities. [ABSTRACT FROM AUTHOR]

The paper discusses the current prognoses of aquaculture development worldwide putting an emphasis on its effect on the environment and the issue of the protection of water reservoirs in different countries. Water consumption in diversified aquaculture systems is presented herein as well as the characteristics of the mechanical and biological water treatment methods in fish farms, with particular attention paid to the recirculating water systems. New aquaculture technologies using post-production waters are presented. The paper provides a discussion on the contribution of aquaculture to the global greenhouse gas emissions and the means of limiting this emission. The effect of climate change on aquatic ecosystems is presented in the context of the changes of the aquaculture production profile. The paper includes a brief presentation of the methods of mitigating the changes with respect to contamination of aquatic ecosystems as well as climate change. Reducing the water footprint can be achieved through selective breeding, species diversification and implementation of more technologically advanced aquaculture systems such as: integrated multi-trophic aquaculture, aquaponics and recirculation systems in aquaculture. The need for certification of fish farms with water recirculation systems is justified in the paper. The issues addressed herein are summarised and the main areas for extending the research promoting preservation of aquatic ecosystems in aquaculture are presented. [ABSTRACT FROM AUTHOR]

The objective of the study was to trace the variability of the hydrochemical conditions in three lakes of the West Pomeranian Voivodeship (Poland) - Starzyca, Maszewskie and Nowogardzkie in the annual cycle. The research was done in 2018-2019, and samples for analysis were collected 4 times a year. All analyses were performed applying standard methods. Such hydrochemical indices were determined as dissolved oxygen, chemical oxygen demand, content of orthophosphates, total phosphorus, nitrite, nitrate, ammonium, chlorophyll a and iron. The study showed that all lakes in the research cycle were characterised by a polymictic type of water mixing, and the trophic level, based on the adopted criteria, indicated advanced eutrophy, which may also be caused by anthropogenic pressure. Oxygen conditions characterised by deoxidation of the waters in the bottom layer in the spring and summer seasons, and clear oxygenation in the surface water layer (in Lake Maszewskie reaching even 188.5% in the spring) confirm the significant advancement of the eutrophication process. The supply of phosphorus and nitrogen in spring from pelagic waters in the waters of the examined lakes influences concentrations of chlorophyll a in the summer. The influence of "internal supply" (bottom waters and bottom sediments) on the amount of nutrients available for autotrophs is clearly visible in the analysed lakes - an increase in nitrogen and mineral phosphorus concentrations in relation to surface waters was observed in the bottom layer. [ABSTRACT FROM AUTHOR]

Magnetoreception is the ability of organisms to perceive magnetic fields in the surrounding environment and changes in its properties such as field direction, intensity and gradient, where the effect on organisms can manifest as an array of reactions. As the magnetic sense is found in many taxa, both evolutionarily young and old, it can be assumed that magnetoreception came into existence as one of the first sensory systems. Many studies on the effect of magnetic fields on fishes have considered both fishes that migrate for long distances and those that are more or less sedentary. Research has focused on tracing the perception of the geomagnetic field by fishes and understanding magnetic fields that are smaller and larger than the ambient Earth's geomagnetic field. The question of the effect of magnetic fields of values higher than the Earth's is gaining importance with the increasing effect of anthropogenic magnetic and electromagnetic fields in aquatic ecosystems. This review draws together the results of studies on the effect and reception of natural and human‐generated magnetic fields on fishes at various stages of ontogeny, chronologically arranged from gametes, through embryonic development, embryonic and larval motor function, directional reactions of embryos and larvae, orientation of fishes, to the mechanisms of magnetic field reception. The present state of knowledge indicates a common nature of effect on various ontogenetic stages of fishes. However, understanding of the mechanisms of magnetic sense in fishes and its relevance for ecological outcomes highlights that further progress requires more detailed research. [ABSTRACT FROM AUTHOR]

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The objective of the study was to determine the rate of growth and cytotoxicity of mycelium of fungus-like organisms Saprolegnia parasitica on media with variable form of available carbon and nitrogen (Sabouraud Dextrose Agar (SDA), Malt Extract Agar (MEA), Potato Dextrose Agar (PDA), Czapek-Dox Agar (CDA)) in magnetic field of 1, 5 and 10 mT. The growth rate of S. parasitica in magnetic field was most varied on SDA medium: the mycelium growth was the slowest in the field of 5 mT compared to the remaining experimental variants and to the control. On MEA and PDA media the growth rate did not vary among the tested field values and the control. The kind of medium and magnetic field had an effect on cytotoxicity of S. parasitica -- on SDA medium the mycelium cytotoxicity was reduced to the greatest extent in magnetic field of 5 mT. The phenomenon can be used to increase the effectiveness of stocking material production. [ABSTRACT FROM AUTHOR]

Effects of water salinity (3.0-9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel ( Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5-9.0 PSU), higher than that prevailing in the species's spawning grounds in the Baltic Sea, resulted - similarly to the low-end salinity - in disturbed development and growth of the embryos. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize in detail the reproductive strategy, course of embryogenesis, and development of larvae in three species of fishes of the genus Cichlasoma : the green terror ( Andinoacara rivulatus ), the red discus ( Symphysodon discus ), and the jaguar cichlid ( Parachromis managuensis ). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. The developing eggs were observed under a microscope (Carl Zeiss Stereo Discovery. V12 and Nikon 2000SE software (NIS-Elements F 4.30.01 64-bit) from fertilization to larval hatching until complete yolk-sac resorption. The largest average number of eggs per female was found in the jaguar cichlid (x¯ = 2991 eggs), a smaller average number of eggs was shown in the green terror (x¯ = 922 eggs), and the red discus showed the smallest average number of eggs (x¯ = 300 eggs). There were significant differences in the sizes of the eggs of the studied species: jaguar cichlid eggs were the smallest (1.060 ± 0.05 mm 3 ), red discus eggs were larger (1.070 ± 0.07 mm 3 ), and green terror eggs were the largest (1.365 ± 0.16 mm 3 ). The embryogenesis time in the red discus was 2132 °H (82 Hpf), in the green terror it was 2158 °H (83 Hpf), and the longest in the jaguar cichlid was 2470 °H (87 Hpf). At the end of embryogenesis, the average size of the larvae after hatching was measured (red discus x¯ = 4.346 mm, green terror x¯ = 5.203 mm, and jaguar cichlid x¯ = 5.301 mm) and the time of yolk-sac resorption from the moment of hatching to the transition from endogenous to exogenous feeding was determined (jaguar cichlid 5 days, green terror 6 days, and red discus 3 days). The results of this study may contribute to the development of reproductive biotechnology for the studied fishes that could be used in aquaculture and, thus, help protect them in their natural habitats.