If that's the line that runs down the middle of the fillet i cut that out making the fillet 2 parts 'meaty' and 'crispy'. Thats the 'fishy' tasting part of the fish and part of getting ready to fry fish to me. Wife likes fish taste so sometimes we cook the fillet as it falls.--shu

PS we have the blue green algae in the Harris chain so we didn't eat many fish for a couple years but the fishermen are still here so we went back to eating them.