The color of awabi is always different and the shades varying from side to side depending on the outer leading edge which in the photo has a tinge of brown orange. This is normal. I was asked a question about why sushi chef’s use the bottom edge of their knife to penetrate the fish. If you notice, the fish has a few cuts that are inflicted onto the surface and penetrate the body. I believe that this relates to “katai”, the hardness that certain shellfish impose. The cuts are made by the chef automatically to assist the chewing, it is a cut to; one, give already an interior softness as the surface is hard and two to promote easy chewing. Either way, what matters is the size of the sushi and the quality of the fish relates to the size.

For example, the larger the size of a lobster, the worse the taste, the smaller the sweeter. There is an optimization when it comes to fish and size. Size relates to age and species and often the growth ridges are a sign. On farmed the ridges are very different from wild caught abalone. The females are often more tasty, and if you look at the underside interior of the animal you can see a white area and this is the sperm (a male). The darker area beside the white area is the guts of the animal.

There are so many species of abalone: http://www.marinebio.net/marinescience/06future/abspdiv.htm