Which method is safe for killing harmful parasites in fish?

Freezing is a safe method for killing harmful parasites in fish. This process involves placing the fish at specific low temperatures for a certain duration, which effectively eliminates parasites such as Anisakis and others that can pose health risks to consumers. According to food safety guidelines, freezing fish at -20°F (-28.9°C) for a minimum of seven days (or at -35°F for a shorter period) is effective in destroying these harmful organisms.

While washing fish can help remove surface contaminants, it does not penetrate the flesh or deal with any parasites that may be present. Similarly, cooling fish merely reduces the temperature but does not reach the levels needed to eliminate parasites. Therefore, freezing stands out as the only reliable method among the options provided for ensuring that fish is free from harmful parasites.