title: Mercury in Forage Fish from Mexico and Central America: Implications for Fish-Eating Birds.
abstract: Mercury (Hg) is a global contaminant of aquatic food chains. Aquatic birds, such as the osprey (Pandion haliaetus), with migratory populations breeding in Canada and the northern United States and wintering in the Central and South America, can be exposed to mercury on both the breeding and wintering ranges. We examined Hg levels in 14 fish taxa from 24 osprey wintering sites identified from satellite telemetry. Our main goal was to determine whether fish species that feature in the diet of overwintering and resident fish-eating birds reached toxicity thresholds for Hg. Mean Hg levels in fish whole carcasses ranged from a high of 0.18 µg g(-1) (wet weight) in Scomberomorus sierra to a low of 0.009 µg g(-1) in Catostomidae. Average Hg levels were within published toxicity threshold values in forage fish for only two sites in Mexico (Puerto Vallarta and San Blas Estuary), and all were marine species, such as mackerel (Scomberomorus sierra), sea catfish (Ariopus spp.), and sardinas species (Centropomus spp.). Except for one sample from Nicaragua, sea catfish from Puerto Morazan, none of the fish from sites in Central America had Hg levels which exceeded the thresholds. Nonmetric multidimensional scaling revealed geographical differences in Hg levels with significant pairwise differences between sites along the Pacific Ocean (Mexico) versus the Bay of Campeche, partly due to differences in species composition of sampled fish (and species distributions). Hg increased with trophic level, as assessed by nitrogen stable isotope ratios (δ(15)N but not δ(13)C), in freshwater and marine, but not estuarine, environments. Hg concentrations in forage fish do not account for the elevated Hg reported for many osprey populations on the breeding grounds, thus primary sources of contamination appear to be in the north.
authors.affiliation: Environment Canada, Science and Technology Branch, Pacific Wildlife Research Centre, 5421 Robertson Road RR# 1, Delta, BC, V4K3N2, Canada. john.elliott@ec.gc.ca.|Applied Animal Biology, University of British Columbia, Vancouver, BC, Canada. john.elliott@ec.gc.ca.
authors.forename: John E
authors.initials: JE
authors.lastname: Elliott
authors.affiliation: Aquila Conservation & Environment Consulting, 75 Albert Street, Suite 300, Ottawa, ON, K1P 5E7, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Kirk
authors.affiliation: McGill University, Sainte-Anne de Bellevue, PQ, H9X 3V9, Canada.
authors.forename: Kyle H
authors.initials: KH
authors.lastname: Elliott
authors.affiliation: Environment Canada, Science and Technology Branch, National Wildlife Research Centre, Ottawa, ON, K1A 0H3, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Dorzinsky
authors.affiliation: Environment Canada, Science and Technology Branch, Pacific Wildlife Research Centre, 5421 Robertson Road RR# 1, Delta, BC, V4K3N2, Canada.
authors.forename: Sandi
authors.initials: S
authors.lastname: Lee
authors.affiliation: Universidad Veracruzana, Xalapa, Veracruz, 91090, Mexico.
authors.forename: Ernesto Ruelas
authors.initials: ER
authors.lastname: Inzunza
authors.affiliation: Applied Animal Biology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Kimberly M T
authors.initials: KM
authors.lastname: Cheng
authors.affiliation: Environment Canada, Science and Technology Branch, National Wildlife Research Centre, Ottawa, ON, K1A 0H3, Canada.
authors.forename: Tony
authors.initials: T
authors.lastname: Scheuhammer
authors.affiliation: Environment Canada, Science and Technology Branch, 201-401 Burrard Street, Vancouver, BC, V6C 3S5, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Shaw
mesh_terms: D000818:Animals; D001717:Birds; D002489:Central America; D005399:Fishes / Q000378:metabolism*; D020387:Food Chain; D008628:Mercury / Q000378:metabolism*; D008800:Mexico; D010473:Perciformes; D018570:Risk Assessment; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury