title: Selective exploitation of large pike Esox lucius--effects on mercury concentrations in fish populations.
abstract: The present study outlines two main trends of mercury transfer patterns through the fish community: 1) the Hg concentrations increase with increase in the trophic level, with top predators having the highest concentrations, and 2) a fast growth rate may dilute the concentrations of Hg in fish muscle tissue (growth biodilution). In 2004, an extensive reduction in number of large pike (Esox lucius L.), was initiated by selective gillnet fishing in Lake Arungen, Norway, in order to increase the pike recruitment due to an expected reduction in cannibalism. In this connection, total mercury (THg) concentrations in the fish community were studied both before (2003) and after (2005) the removal of large pike. The delta(15)N signatures and stomach content analyses indicated that pike and perch (Perca fluviatilis L.) occupied the highest trophic position, while roach (Rutilus rutilus (L.)) was at the lower level, and rudd (Scardinius erythrophthalmus L.) at the lowest. The piscivores, pike and perch, had the highest concentrations of THg. The biomagnification rate of THg through the food web in the fish community was 0.163 (per thousand delta(15)N), with the highest uptake rate (0.232) in perch. A significant decrease in THg concentrations was found in all fish species in 2005 compared to 2003. Removal of the top predators in an Hg contaminated lake might thus be an important management tool for reducing Hg levels in fish, thereby reducing health risk to humans.
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432 As, Norway. chhatra.sharma@gmail.com
authors.forename: Chhatra Mani
authors.initials: CM
authors.lastname: Sharma
authors.forename: Reidar
authors.initials: R
authors.lastname: Borgstrøm
authors.forename: Jørgen Sinkaberg
authors.initials: JS
authors.lastname: Huitfeldt
authors.forename: Bjørn Olav
authors.initials: BO
authors.lastname: Rosseland
mesh_terms: D000818:Animals; D049628:Body Size / Q000187:drug effects* / Q000502:physiology; D003530:Cyprinidae / Q000502:physiology; D004784:Environmental Monitoring; D017859:Esocidae / Q000502:physiology*; D005399:Fishes; D005618:Fresh Water; D005766:Gastrointestinal Contents / Q000737:chemistry / Q000187:drug effects*; D008628:Mercury / Q000378:metabolism / Q000633:toxicity*; D009587:Nitrogen Isotopes; D009664:Norway; D010471:Perches / Q000502:physiology; D013045:Species Specificity; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D009587:Nitrogen Isotopes; D014874:Water Pollutants, Chemical; D008628:Mercury