What causes these black marks on a fish like this?

Type: Nontidal
Region: Central
Location: Tridelphia Reservoir

I caught this fish today (3/26/11) at Triadelphia Reservoir, while fishing from a kayak. It was sunny, but the water was still cold, high, and stained. I tossed a white spinner bait to a point with a submerged tree and hooked up with a fish. It was pulling the kayak around and ended up being a 20 inch largemouth. It had some unusual black spots on it. Does the DNR know what causes these black marks on a fish like this?

DNR RESPONSE via Dr. Joe Love, Inland Fisheries Biologist - There�s no consensus on what causes these black spots. Based on conversations I�ve had with folks fishing across the country, the black spots are commonly found on largemouth bass from other states too. I believe that the spots may be inherited and I�ve found them on young-of-year bass. There have been other hypotheses, such as melanin production because of sun exposure and seasonal changes in water quality. No one is really sure, though. Some work done a few years ago demonstrated that there was no health risk to the fish because of the spots. It seems natural, widespread, and non-threatening. I�d like to know more about what causes it as well, but the research isn�t there just yet.