TY JOUR TI The content of mercury and lead in the feed base of valuable fish species of the Caspian Sea KW heavy metals KW accumulation KW hydrobionts KW invertebrates of the Caspian Sea JO Fisheries AU Ershova, T.S. AU Chaplygin, V.A. AU Zaitsev, V.F. AU Khursanov, A.S. AU Shaboyants, N.G. PY 2021 IS 2021 PB FSBI "TSUREN"