Wild versus Farmed Fish: Metal Concentration and Biomagnification Trends in the Food Web of a Chinese Reservoir

Abstract

Natural and anthropogenic elemental contamination is widespread in the environment. This is especially true in China, a country with rapid industrial and economic growth. Some metals can be toxic at very low concentrations, rapidly accumulating within fish tissues and other organisms. As fish are an important part of the Chinese diet, food web transfer and biomagnification trends of As, Cd, Co, Cr, Cu, K, Ni, Pb, Rb, Se and Zn are assessed for fish from a reservoir in eastern China. This study site, with 1,078 islands and prized freshwater fish species, contains 13 families and 86 fish species. Commonly-consumed farmed fish from a range of trophic levels were sampled, including Silurus asotus, Aristichthys nobilis, Ictalurus punctatus, Carassius auratus, Ctenopharyngodon idella, Micropterus salmoides and Hypothalmichthys molitrix. Wild piscivorous fish sampled include Siniperca chuatsi, Erythroculter mongolicus, Erythroculter illishaeformis and Channa argus argus. Our questions for this study are: (1) Are metal accumulation trends and concentrations in wild versus farmed fish species different? (2) Do trends in metal concentration between fish markets in a large city and a fishing town differ? Concentrations of Cd, Co and Pb were below reliable ICP-OES detection limits. As, Cu and Zn concentrations were highest in farmed species, whereas Cr, K, Ni, Rb and Se were highest in wild species. δ15N values were used to estimate trophic position. Results obtained suggest significant biomagnification of Se at successive trophic levels and marginally significant biomagnification trends for Rb. All other relationships between elemental concentration and trophic position indicated a lack of biomagnification. Anthropogenic sources from industrial activities surrounding the reservoir may contribute to elevated Cr and Se in fish, while ambient pH and temperature differentials could play a role in the increased bioavailability of Rb in the region.