The shark described a circle around the shoal of fish.

这条鲨鱼围绕着鱼群游动。

《牛津词典》

Mercury levels are high in marine fish, too—particularly in larger species, such as shark, tuna, and swordfish.

海洋鱼类中的汞含量也很高——尤其在体型较大的鱼类体内，如鲨鱼、金枪鱼和旗鱼。

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One reason is that overfishing of sharks and related fish has reduced the size of some shark populations.

VOA: special.2009.06.16

The British scientists had requested the pictures to learn if the shark was the same fish they had observed on their side of the Atlantic.

VOA: special.2009.06.16

Larger fish such as shark, king mackerel, swordfish, and tilefish tend to be highest in mercury because they eat smaller fish and consume the mercury in them as well.

CNN: Seafood benefits outweigh risks, government says

The risk increases as off-shore pollution increases and as more people eat more fish including shark.

CNN: Beware of shark meat, FDA warns

Levels of mercury in fish other than shark, swordfish and marlin did not give cause for concern.

BBC: Predatory fish health warning