It's true. There are right handed and left handed halibut. By far the majority of all halibut are right handed while the lefty's are more rare. Not exactly one in a million, but biologist claim that 1 in 20,000 are left handed.
How do you tell the difference? The eyes and dark skin are on the left side of the fish. In the photo above the left handed halibut is on the right and the "normal" halibut is on the left. For me, the best way to tell them apart is when halibut are hung on a fish rack. All good charters will hang halibut with the white side facing out and the head up. The stomach on a "normal" halibut will be on the left side (it will look like the fish swallowed a baseball or softball). The stomach on a left handed halibut will be on the right side.