Mercury

<p><a href="http://en.wikipedia.org/wiki/Fish" title="Fish" >Fish</a>&nbsp;and&nbsp;<a href="http://en.wikipedia.org/wiki/Shellfish" title="Shellfish" >shellfish</a>&nbsp;have a natural tendency to concentrate mercury in their bodies, often in the form of&nbsp;<a href="http://en.wikipedia.org/wiki/Methylmercury" title="Methylmercury" >methylmercury</a>, a highly toxic organic compound of mercury.&nbsp;</p>

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Species of fish that are high on the&nbsp;<a href="http://en.wikipedia.org/wiki/Food_chain" title="Food chain" >food chain</a>, such as&nbsp;<a href="http://en.wikipedia.org/wiki/Shark" title="Shark" >shark</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Swordfish" title="Swordfish" >swordfish</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/King_mackerel" title="King mackerel" >king mackerel</a>,&nbsp;

<a href="http://en.wikipedia.org/wiki/Bluefin_tuna" title="Bluefin tuna" >bluefin tuna</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Albacore_tuna" title="Albacore tuna" class="mw-redirect" >albacore tuna</a>, and&nbsp;<a href="http://en.wikipedia.org/wiki/Tilefish" title="Tilefish" >tilefish</a>&nbsp;contain higher concentrations of mercury than others.&nbsp;</p>

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As mercury and methylmercury are fat soluble, they primarily accumulate in the&nbsp;<a href="http://en.wikipedia.org/wiki/Viscera" title="Viscera" class="mw-redirect" >viscera</a>, although they are also found throughout the muscle tissue.<sup id="cite_ref-100" class="reference" ><a href="http://en.wikipedia.org/wiki/Mercury_(element)#cite_note-100" >[101]</a></sup>&nbsp;</p>

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When this fish is consumed by a predator, the mercury level is accumulated.&nbsp;</p>

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Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the&nbsp;<a href="http://en.wikipedia.org/wiki/Food_chain" title="Food chain" >food chain</a>&nbsp;amass body burdens of mercury that can be ten times higher than the species they consume. This process is called&nbsp;<a href="http://en.wikipedia.org/wiki/Biomagnification" title="Biomagnification" >biomagnification</a>.&nbsp;<a href="http://en.wikipedia.org/wiki/Mercury_poisoning" title="Mercury poisoning" >Mercury poisoning</a>&nbsp;happened this way in&nbsp;<a href="http://en.wikipedia.org/wiki/Minamata,_Kumamoto" title="Minamata, Kumamoto" >Minamata</a>,&nbsp;<a href="http://en.wikipedia.org/wiki/Japan" title="Japan" >Japan</a>, now called&nbsp;<a href="http://en.wikipedia.org/wiki/Minamata_disease" title="Minamata disease" >Minamata disease</a>.</p>