1. INTRODUCTION The aim of this study was to compare changes in the mercury content and fatty acid profiles of muscles, ovaries and oocytes of maturing female European eels during artificial maturation after hormonal stimulation with carp pituitary homogenate (CPH) under controlled conditions. Joanna NOWOSAD a, Dariusz KUCHARCZYK a, Joanna ŁUCZYŃSKA b, Katarzyna TARGOŃSKA a, Mateusz SUCHONOS a, Tomasz CZARKOWSKI c, László HORVÁTH d, Tamás MÜLLER d a Department of Lake and River Fisheries, University of Warmia and Mazury in Olsztyn, Poland b Department of Commodity Science and Food Analysis, University of Warmia and Mazury in Olsztyn, Poland c Warmia and Mazury Centre for Agricultural Consulting, Olsztyn, Poland d Department of Fish Culture, Szent István University, Páter K. u. 1, H-2100 Gödöllő, Hungary *corresponding author e-mail : darekk56@gmail.com darekk56@gmail.com CHANGES IN MERCURRY CONTENT AND FATTY ACIDS PROFILES DURING ARTIFICIAL MATURATION OF EUROPEAN EEL (Anguilla anguilla L.) FEMALES AKNOWLEDGMENTS This study was partially financed under the auspices of the project “Innovations in finfish aquaculture with special references to reproduction”, Operational Programme Sustainable Development of the Fisheries Sector and Coastal Fishing Areas 2007-2013" (OR14-61724- OR1400003/09/10/11).www.InnovaFish.pl RESULTS AND DISCUSSION. In order to improve the artificial reproduction of the eel, a detailed analysis of the entire ovary and gamete maturation process is required. The changes in the biochemical composition of the body tissues, mainly muscles and ovaries, are an indicator of the changes in the whole process. The knowledge of those changes and their dynamics will help to elucidate the process of vitellogenesis and final oocyte maturation. It will also help to understand what chemical substances are necessary for the process. The concentration of mercury in eel muscle and ovary was slight related to the eel length and weight. Much higher concentration was noted in eel muscle (0.3-0.4 mg per kg of wet BW) than in the ovary and eggs (0.03 and 0.01 respectively). The concentration of mercury and fatty acid profiles was changed during females’ maturation, especially in the muscle. MATERIAL AND METHODS Eel brooders were caught during commercial fishing activities in freshwater in the Mazury region (the north-east of Poland) as fish which start their spawn migration (at the end of May). The collection of fish was made during few following days. After being caught, the fish were transported to the laboratory of the Department of Lake and River fisheries, University of Warmia and Mazury, Olsztyn, where they were put into a 1 m 3 tank, operating in closed water circulation. The initial water temperature was 12°C (± 0.2°C) and later was increased to 15 °C. The oxygen level in the water was at least 6 ppm. The chemical composition (fatty acid profiles) of gonads and ovulated eggs and mercury level in muscles, gonads and eggs were analyzed. Fig. 1. Mercury content in European eel muscle, ovary and ovulated oocytes.