More than likely the darker filet was the side of the fish that was filleted first. Once the filet knife begins to make its cut into the flesh of the fish, the blood begins to run to that particular side of the fish. If there is some life left when you are cleaning your catch, the heart will actually pump the blood to the side of the fish that is cut first.
After you turn your catch over and filet the remaining side, you will more than likely notice a much lighter color.
To correct this age old problem, you simply need to bleed your catch before it is deposited into your cooler or live well.
With a sharp knife make a cut just behind the gill plate, right in the middle of the fish. Most of the blood will drain from the incision.
If you have a live well, make this cut, then place the fish into the live well until all of the blood is drained out. Or you can simply hold the fish in the water.
Once the blood is drained from the fish, place your catch in an iced-down cooler or fish box. When it comes time to clean your catch, you will be astonished at the white filets.
Use several sheets of newspaper when cleaning your catch. This will help prevent your filets from coming in contact with any undesirable fluids that may ruin the taste of your catch.
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