Publisher :
Place of publication :
Publication year : 2009
Thematic : Marine Resources
Language : English
Note
Mercury distribution in the oceans is controlled by complex biogeochemical
cycles, resulting in retention of trace amounts of this
metal in plants and animals. Inter- and intra-specific variations in
mercury levels of predatory pelagic fish have been previously
linked to size, age, trophic position, physical and chemical environmental
parameters, and location of capture; however, considerable
variation remains unexplained. In this paper, we focus on
differences in ecology, depth of occurrence, and total mercury
levels in 9 species of commercially important pelagic fish (Thunnus
obesus, T. albacares, Katsuwonus pelamis, Xiphias gladius, Lampris
guttatus, Coryphaena hippurus, Taractichthys steindachneri, Tetrapturus
audax, and Lepidocybium flavobrunneum) and in numerous
representatives (fishes, squids, and crustaceans) of their lower
trophic level prey sampled from the central North Pacific Ocean.
Results indicate that total mercury levels of predatory pelagic
fishes and their prey increase with median depth of occurrence in
the water column and mimic concentrations of dissolved organic
mercury in seawater. Stomach content analysis results from this
study and others indicate a greater occurrence of higher-mercury
containing deeper-water prey organisms in the diets of the deeperranging
predators, X. gladius, T. obesus, and L. guttatus. While
present in trace amounts, dissolved organic mercury increases with
depth in the water column suggesting that the mesopelagic habitat
is a major entry point for mercury into marine food webs. These
data suggest that a major determinant of mercury levels in oceanic
predators is their depth of forage.
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Keywords : Tamiops macclellandii
Encoded by : Pauline Carmel Joy Eje
