A fair and effective counterclaim to the argument presented could be:
"While studies indicate that eating fish may have health risks, it is important to note that fish is also a valuable source of essential nutrients, including omega-3 fatty acids, which have numerous health benefits, such as reducing the risk of heart disease. Moderation and choosing fish with lower mercury levels can help maximize the benefits while minimizing the risks."
This counterclaim acknowledges the health risks associated with fish consumption but highlights the nutritional benefits and suggests an approach to mitigate the risks, making it a balanced and nuanced response.