O.M. Popoola*, A. Ebiwonjumi Department of Fisheries and Aquaculture, Federal University of Technology, Akure, Nigeria (Manuscript received 31 October 2020; accepted for publication 20 February 2021) Abstract. The pattern of morphological variations among Oreochromis niloticus (Linnae

N. Georgieva, Z. Yaneva, D. Dermendzhieva, V. Kotokova Abstract. The aim of the present study was ecological monitoring of Cr (VI) concentrations in surface waters from Stara Zagora Region used in agriculture. The research goal was accomplished by: determining Cr (VI) concentrations i