A few weeks ago, someone sent us this photograph of a shark taken along the shores of Sanibel Island. They asked if we could identify it, but due to the anatomical similarities between many shark species, that’s no easy feat. So we asked a group of shark biologists to help us out and ensure that the identification was as accurate as possible.
First, we reached out to former University of Florida shark expert Jason Seitz. Jason mused that it could be a lemon or bull shark based on his previous fishing experience and the visibility of the dorsal fins. In the photo, the second dorsal fin was below the surface of the water, suggesting that it was relatively small in size. A smaller second dorsal fin is a good field mark for bull sharks, so Jason thought that this species was the presumable choice. Jason also ruled out a black-tip shark due to the lack of pigmentation on the dorsal.
Even though these species were both plausible suggestions, Robert E. Hueter, Ph.D., Director of the Center for Shark Research at the Mote Marine Laboratory, had a different idea. Based on the photo, Dr. Hueter decided that the fin shape and position weren't exactly fit for a bull shark. He confirmed that the species was, in fact, a sandbar shark – it is typical for them to swim near shore in the winter months in SW Florida, passing through on a migratory journey or following their prey. And so we found our answer.
It’s always fascinating to catch a glimpse of shark fin from the beach, but this example just goes to show that fish identification isn’t always as easy as it might seem. From land, it’s hard to see what is swimming below the waves, and sometimes it takes great experience and skill to solve the mystery. Luckily, there are biologists ready and willing to step up to the challenge!