UNEXPECTEDLY HIGH MERCURY LEVEL IN PELLETED COMMERCIAL FISH FEED

An unexpectedly high mercury (Hg) level was found in a pelleted commer cial fish feed used to feed fish in laboratory and fish farm settings. Mean total Hg (T-Hg) concentration in the commercial fish pellets was 66 ppb (ranging from 35 to 90 ppb). Mean total selenium (T-Se) concen tration in the pellets was 1,120 ppb (ranging from 790 to 1,360 ppb). Total Hg and Se in the whole blood of Sacramento blackfish and in the fish feed were determined by inductively coupled plasma-mass spectrome try (ICP-MS). During a 10-week sampling period T-Hg in blood fluctuate d between 35 and 56 ppb. A highly significant, positive correlation (r = 0.99, p < 0.01) was found between T-Hg in the fish blood and in the fish feed through the sampling period. On the other hand, no correlat ion was found between T-Se in the fish feed and T-Hg or T-Se blood lev el. Researchers working with fish in Hg studies need to know that fish pellets may contain Hg and to consider the influence of these pellets in their results.