Sharks. They’re here now, they were here before, and they’ll (probably) be here in the future. Few people who live in or visit Birmingham know that sharks dwell in the city’s center. This isn’t the stuff of urban legends – this is science at the McWane Science Center.
The Center has live sharks and rays (their close evolutionary relatives) on display in a special pool where you can actually touch them. Though touching a shark might be thrilling and a little scary for some, it’s not at all hazardous. The shark species chosen are small and gentle-natured with no interest in finger food. And the rays, normally armed with serrated spines at the base of their tail, have had their spines clipped. Though the spines can grow back, Center staff inspects the rays daily and trim the spines. It’s not unlike us getting our fingernails clipped.
The species at the Center include Bonnethead Sharks, White-spotted Bamboo Sharks, Southern Stingrays, and Cownose Rays. As the maps and information posted above the tank explain, all are native to Alabama’s Gulf Coast except the Bamboo Shark. All are also members of the same taxonomic group, Elasmobranchii, a subclass of the class Chondrichthyes. Like the rest of the fish in this class, the sharks and rays share similar characteristics. In particular, they have bones made of cartilage, the same flexible structure at the ends of your long bones and in the tip of your nose. All Elasmobranchs have rigid fins, five gill clefts, and special scales on their skin that are silky smooth when stroked head to tail, but rough as sandpaper when stroked tail to head. As a whole, sharks and rays are predators and scavengers of dead animals. Some species specialize in particular types of prey, while others have a broad diet.
So, thanks to the Center, we have sharks in Birmingham. But how were they here before? Paleontologists have found fossils of the earliest shark-like fish in rocks that formed hundreds of millions of years ago. Since cartilage doesn’t often fossilize, paleontologists rely on fossilized shark scales and teeth to study the evolutionary history of sharks. Fortunately, sharks shed their teeth on a regular basis, and shark teeth can be the most common fossil in some ancient rocks. When you visit the Center, you can examine the teeth of some of Alabama’s ancient sharks under the microscope at a station near the touch tank. You can also dig through sediment collections and find shark teeth in the Explore lab on the second level next to the Museum Collections Center.
Paleontologists believe modern sharks’ most primitive ancestors were swimming in the planet’s oceans as far back as the Ordovician period (488–444 million years ago). They didn’t look a lot like today’s sharks, but they had most of the traits shared by modern Elasmobranchs. Birmingham has a lot of rock that formed during the Ordovician period, plus other marine rocks formed in later geologic periods. That means primitive sharks swam above what is now Birmingham for many millions of years in its ancient history. Fish resembling our modern sharks didn’t appear until about 100 million years ago, in the Cretaceous period (146–65.5 million years ago), a time when sea levels in Alabama covered what is now the Coastal Plain (the southern half of the state). Birmingham doesn’t have rocks from this time period, but shark teeth are abundant in nearby rocks formed in this time.
Will sharks ever swim in Birmingham again (outside of the McWane Science Center)? Probably, given enough time. The earth is ancient, and there’s every indication it will be around for several billion more years. And if the past is a good predictor of the future, there will be times – probably millions of years from now – when most of what is now Alabama will be once again submerged below oceanic waters. Of course, the Southern Appalachian Mountains in which Birmingham was founded will have to erode down to a near-level plain to allow sea levels to reach where the city is now.
But there is one thing that could prevent sharks from plying the oceans of the future – extinction. Though sharks have occupied the planet for over 400 million years, many modern species may not survive this century. Humans have already severely disrupted many of the oceanic food chains that support healthy shark populations. And fishing for sharks directly – primarily for Asian food markets – and indirectly, as bycatch (fish caught unintentionally along with other fish), has taken a great toll on many species.
The decline in shark populations is causing economic losses in some portions of the seafood industry. As a wall display near the Center’s shark and ray touch tank explains, coastal sharks eat lots of rays, and rays eat lots of shellfish, including oysters and scallops. People also eat lots of oysters and scallops, and in some areas where sharks have been nearly eliminated – the Chesapeake Bay is one notable example – the seafood fishery dependent on the shellfish is in steep decline. That has severely damaged the economies of several coastal communities.
Experiences like the shark and ray touch tank at the McWane Science Center are teaching the next generation to admire and appreciate sharks instead of fear them. Hopefully, some of these young folks will go on to successfully support and advocate for the protection of sharks.
-R. Scot Duncan