Induced spawning in Eurasian perch, Perca fluviatilis L., was studied using human chorionic gonadotrophin (hCG) or acetone-dried common carp pituitary with or without hCG, The dose administered to fish was 5700 IU hCG kg"' or 4,0 mg kg~^ carp pituitary with or without 500-700 IU hCG kg~i for females and 2850 IU hCG kg"' or 2,0 mg kg~' carp pituitary with or without 250-350 IU hCG kg"^ for males. There were no statistically significant differences in quantity of milt in treated and control groups, although the best result was observed when males were treated with a triple injection of hCG and carp pituitary extract, Male spermiating success, expressed as a quantity of milt, was negatively correlated with fish weight. All females treated in this experiment had oocytes at the same division, so time of ovulation was highly synchronous. Spawning success, expressed as a spawning eflectivity coefficient (S^), was highest in fish treated with the triple injection. Spawning methods described in this paper were successful, even though hormones from another order of fish were used.

Induced spawning in perch, Perca fluviatilis L., was studied using follicle stimulating hormone and lutenizing hormone (FSH ϩ LH) with the addition of pimozide or metoclopramide. The doses administered to fish were: 75 IU kg -1 of FSH ϩ LH with 5 or 10 mg kg -1 of pimozide (P) or metoclopramide (M) in females, and 25 IU kg -1 of FSH ϩ LH with 2.5 or 5 mg kg -1 of P or M in males. Hormonal injections in males (except the injection of FSH ϩ LH with 10 mg kg -1 of M) did not influence the quantity of milt obtained. All females treated in this experiment had oocytes at the same stage of nucleus migration, so the time of ovulation was very synchronous, i.e. 16-24 h after injection. The relationship between the quality of the eggs, expressed as a survival to eyed-egg stage, and latency was inverse. Spawning success, expressed as a spawning effectiveness coefficient (S e ), was highest in the fish that had been treated with FSH ϩ LH with a higher dose of M. *Injection from 0.9% NaCl. 132

The aim of this study was to determine the structure of zooplankton in three artificial water reservoirs, the technological function of which is to pre-treat waters from a drainage system of a brown coal open mine by removing inorganic suspension. The background for the zooplankton qualitative and quantitative analyses was the hydrochemical conditions in the individual reservoirs. The greatest zooplankton abundance (N), number of taxa (n), Shannon’s diversity (H'), and species eveness (J') was noted in reservoir Chabielice (Nmean = 1311 ind. L−1, n = 26, H' = 2.09, J' = 0.64) which was dominated by eurytopic Rotifera species (Keratella cochlearis,Keratella tecta,Keratella valga,Polyarthra longiremis,Filinia longiseta). Their abundance was positively correlated with water pH and nutrient concentrations. Reservoir Kamień was characterized by the highest mean values of total suspension (9.6 mg L−1), chlorophyll a (Chl a) content (10.4 μg L−1), and water temperature (20.0 °C). These factors significantly correlated with crustacean biomass. The thermal-oxygenation conditions, low trophic level, and low productivity of the water (Chl a = 5.4 μg L−1) in reservoir Północny determined the overall low zooplankton abundance (Nmean = 153 ind. L−1). Artificial water bodies of opencast mine drainage systems are biologically unstable, but they do have some characteristics of natural ecosystems, and they do take over their functions. Zooplankton is an indicator of their ecological functionality. Knowledge gained about such reservoirs could contribute to decision-making about strategies for water reclamation and how to manage it.

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Induced spawning in Eurasian perch, Perca fluviatilis L., was studied using human chorionic gonadotrophs (hCG) or acetone‐dried common carp pituitary with or without hCG. The dose administered to fish was 5700 IU hCG kg‐1 or 4.0 mg kg‐1 carp pituitary with or without 500‐700 IU hCG kg‐1 for females and 2850 IU hCG kg‐1 or 2.0 mg kg‐1 carp pituitary with or without 250‐350 IU hCG kg‐1 for males. There were no statistically significant differences in quantity of milt in treated and control groups, although the best result was observed when males were treated with a triple injection of hCG and carp pituitary extract. Male spermiating success, expressed as a quantity of milt, was negatively correlated with fish weight. All females treated in this experiment had oocytes at the same division, so time of ovulation was highly synchronous. Spawning success, expressed as a spawning effectivity coefficient (Sc), was highest in fish treated with the triple injection. Spawning methods described in this paper were successful, even though hormones from another order of fish were used.