Quote:
Originally Posted by Columbine
Actually, I think there is, and quite logically. Dolphins and those categorized as "small whales" tend to be toothed; this means they eat fish rather than krill and shrimp etc. Fish retain much more mercury than krill, (in fact, shrimp have among the lowest levels of mercury absorption of all sea creatures), which is then in turn absorbed by the secondary and tertiary predators. Unlike large toothed whales, dolphins and small whales don't hunt at great depth, so they encounter more contamination in their prey. Dolphins particularly will hunt in shallows, greatly increasing the risk of contact with mercury from waste. Besides which, the main diet of large toothed whales tends to be squid, which generally have less mercury than fish anyway.
Basically it builds up so that a young dolphin could easily have a higher concentration of mercury than a young whale, although a very old whale will probably have more than an old dolphin, simply by having lived for much. much longer.
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I see your point, and I had considered that possibility too, but minke whales, about 80% of what Japan hunts, feed more on fish than krill, shrimps and squids.