This article discusses how the health benefits of fish override the mercury content;
"The benefits of eating fish have been purported in depth. Many species of fish are rich in omega-3 fatty acids. Omega-3 fatty acids are a polyunsaturated fatty acid (PUFA), vital for brain health, heart health, and growth and development.
One primary benefit of eating fish high in omega-3 fatty acids is that it can reduce inflammation. Most disease states have inflammatory components, including heart disease...."
http://dailyinfusion.com/health-benefits-of-eating-fish-may-override-mercury-content85912/
Source: dailyinfusion.com