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Indestructible Predators or Vulnerable Species: Shark Week at Shedd

A Black Tip Reef Shark (Carcharhinus melanopterus) glides through its habitat.
A Black Tip Reef Shark (Carcharhinus melanopterus) glides through its habitat.

While sharks have the reputation of being indestructible, their populations are actually decreasing and some species are endangered or vulnerable to extinction. As apex predators, sharks play an important role in the ecosystem by maintaining populations of lower trophic levels and serving as an indicator for ocean health.  For Shark Week, Shedd Aquarium is raising awareness about some of its endangered species of sharks and the role we have with these species to protect and conserve them.

The Association of Zoos and Aquariums (AZA) has launched an effort called SAFE: Saving Animals from Extinction, which focuses on the collective expertise within the network of accredited zoos and aquariums and leverages their massive audiences to save species. A combination of overfishing and an overwhelming demand for shark liver oil, cartilage, and meat have posed a serious threat to the shark population. In response, AZA accredited zoos and aquariums, like Shedd, have invested over $2.1 million in shark and ray field conservation, including population studies, research, and tagging. AZA has placed a Species Survival Plan (SSP) in place for a variety of sharks in human care, one of which is managed by Lise Watson, collection manager in Wild Reef at Shedd Aquarium.

Zebra Sharks: Endangered with Species Survival Plan

Zebra sharks (Stegostoma fasciatum) are one of 11 species of sharks at Shedd, there are two male (Seymour and Eli) and three female (Cleo, Vera, and ST10) zebra sharks in total that call Shedd home. The species is listed as “endangered” on the IUCN Red List because they’re hunted for meat, liver oil (used for vitamins) and fins (used for shark fin soup). Each year, 100 million sharks are caught and killed by humans, half of which are unintentional, making people sharks’ greatest threat. In addition, their reef habitat is steadily disappearing.

A Zebra Shark swims through its habitat.
Due to their dark spots, Zebra Sharks are called Leopard Sharks in some parts of the world.

Watson compiles and maintains the studbook for AZA’s SSP for zebra sharks. An SSP is a carefully managed breeding program developed specifically for certain species declining in the wild. The SSP is designed to establish healthy, genetically diverse and sustainable populations at AZA member organization. We’ve had over 100 zebra sharks hatch here since 2004 with Cleo producing 86 of the offspring. Last year, we welcomed six additional zebra shark pups.

DYK: What We’ve Learned about Zebra Sharks

In general, zebra sharks at Shedd are known amongst others as the easiest to work with, gentle and sometimes playful. They get their name from their appearance as pups because when they’re first born the zebra shark pups have dark brown stripes like a zebra. After the sharks reach about two months of age, the stripes morph into dark spots against their creamy color – hence, why other parts of the world refer to them as leopard sharks. Furthermore, each shark has a unique pattern on its head, making it easier to identify who’s who. Zebra sharks can grow to be 7 – 9 feet long and have narrow, flexible bodies that allows them to wiggle in and out of tight spaces to feed on snails, clams and small fishes. Its barbels, or fleshy feelers beside each nostril, help it find food, especially because it prefers to hunt at night.

Unlike other sharks that swim at missile-like speeds, zebra sharks move slowly and enjoy resting on the sandy floor near coral reefs. Sometimes they even prop themselves up on their pectoral fins in order to take some of the pressure off of pumping water to breathe. These relaxed, gentle creatures can be found in the Wild Reef exhibit, along with our sandbar sharks, blacktip reef sharks, Japanese wobbegong and spotted wobbegong sharks. In our Mangrove and Lagoon habitats, we also have whitespotted bamboo sharks and are expecting to welcome a coral catshark soon!

Blacktip Reef Sharks: Near Threatened Species

Blacktip reef sharks are declining in numbers due to overfishing and slow reproduction rate. Their tendency to swim in shallow areas makes them easy prey for fishers using gillnets. They’re also prone to predation by larger shark species and even larger fish like groupers. The species is listed as “near threatened” by the IUCN Red List. Shedd gives the public the opportunity to see and connect with blacktip sharks in person, which allows for our guests to come eye to eye with an animal that is disappearing fast.

Shedd is home to three male blacktip reef sharks, four females, and welcomed eight pups this past spring, which was a first for Shedd’s animal care team. Blacktip reef sharks are slow breeders; since they develop viviparously (within the body), they produce fewer pups in a longer period of time with gestation rate around one year. They can grow to 6 ½ feet in length and weigh around 30 pounds (their light weight compared to other sharks is due to their cartilaginous skeleton). Unlike bony fish, which have a swim bladder to keep them from sinking, a shark’s buoyancy is the result of a large liver that contains oils and fats.

What You Can Do for Sharks

A trainer at Shedd Aquarium interacts with a Zebra Shark.
A trainer at Shedd Aquarium interacts with a Zebra Shark.

Ensuring that these species not only have a place to survive, but also thrive and reproduce to re-build their populations is just one of the important roles aquariums play. Sharks play a vital role in protecting the entire ocean ecosystem that rely on the natural cycle of predation. Globally, shark species are threatened with extinction, but collaboratively, zoos and aquariums are making an impact to sustain these populations.

In addition, plastic is now found on every marine habitat in the world. Did you know that juvenile marine animals are at higher risk of negative impacts from plastic pollution than their adult counterparts? These impacts are particularly significant for the 17 percent of species affected by plastic pollution that are also listed as near threatened, vulnerable, endangered or critically endangered by the IUCN.  The risk is dire; scientists predict that plastics in our oceans will outweigh fish pound for pound by 2050. Reduce your use of single-use plastics, such as plastic bags, straws, utensils and more, which is essential for reducing risks posed by plastic entanglement and ingestion to the health of aquatic animals and ecosystems. Our choices are transforming the ocean, lakes and rivers. Learn more about reusable alternatives and what you can do by visiting, www.ourhands.org.