You are here:
LEVEL AND EXTENT OF MERCURY CONTAMINATION IN OREGON LOTIC FISH
Citation:
Herlihy, A. T., S A. Peterson, AND R M. Hughes. LEVEL AND EXTENT OF MERCURY CONTAMINATION IN OREGON LOTIC FISH. Presented at American Fisheries Society Oregon Chapter, Eugene, OR, February 26-28, 2002.
Description:
As part of the U.S. EPA's EMAP Oregon Pilot project, we conducted a probability survey of 154 Oregon streams and rivers to assess the spatial extent of mercury (Hg) contamination in fish tissue across the state. Samples consisted of whole fish analyses of both small (< 120 mm) and large (> 120 mm) fish at each site, when available. Overall, Hg concentrations ( g/g) in small fish (mean=0.031, SD=0.029), large invertivores (mean=0.055, SD=0.047), and large piscivores (mean=0.284, SD=0.175) were found within fairly narrow ranges, always above detection (0.0025 g/g) and almost always below 0.4 g/g. Given the great diversity in geology, physiography, land use, and ecology across the state of Oregon, the narrow range in fish tissue Hg levels suggests that atmospheric transport is an important vehicle for Hg distribution. Small fish Hg levels were almost always low and showed little meaningful difference among fish taxa. In large fish, Hg concentrations were significantly related to fish length. Piscivores (pikeminnow and bass) had significantly higher Hg concentrations, and the slope of their Hg concentration/length relationship was much steeper than for invertivores. Salmonids, the most commonly occurring fish taxa in Oregon exceeded 0.1 g Hg/g (a criteria deemed protective for fish eating mammals) in an inferred 15% of the stream length where they occurred . Pikeminnows and bass were found at fewer sites, but they exceeded 0.1 g Hg/g in an inferred 96% and 70%, respectively of stream lengths where they occurred.