Sabelfish is also referred to as Black Cod or Butterfish, though Epicurious maintains that it is actually neither. Sabelfish is found in the waters off of Alaska and in the Pacific Northwest.
I've only seen the fish around town recently. First at Bar Crudo (where they served it with a blood orange reduction) and then at Hapuku. The State of Alaska has apparently taken an interest in their Sabelfish population. They have an open job listing for a research surveyer - fishing vessel a must, strictly catch and release.
Sabelfish filets are an unusually solid white, though the flesh is soft and easily sliced. The fish is oily and well-suited to smoking and grilling. I also enjoyed it raw with olive oil, thyme, and a meyer lemon scented salt.