Isothiocyanate, the liver being a detoxification organ does not imply bioaccumulation of toxins in liver because the liver's purpose is to make toxins excretable by conjugating them to water - soluble components; but it does imply that liver will be very high in nutrients needed for detoxification. (westonaprice.org)
In fact, wild fish frequently have higher levels of heavy metals in their nervous systems because of bioaccumulation through natural food chain processes, whereas farmed fish are often fed substances less directly connected to the food chain. (nerdfitness.com)