A marvel of evolution

Education | Ocean Park 19 Jan 2021

The scalloped hammerhead shark is a reminder of the resilient force of evolution constantly at work.

Its scallop-like cephalofoil, or outward lateral extension of the head, inspired a number of hypotheses about its functionality. Some of the common speculations include a precise movement aid and a super sensory receptor.

What is known is that the shark's broad, narrow-bladed head allows its eyes to be located far apart - at both ends of the cephalofoil.

As it rotates its eyes and sweeps its head from side to side, it is endowed with exceptional binocular vision and a full 360-degree view.

With a forked tail and body color shading from greyish brown on top to white below, the shark has excellent camouflage in open water.

Up to 4.3 meters long and weighing about 150 kilograms, this majestic fish is generally found in warm-temperate and tropical seas around the globe.

Adults spend most of their time offshore. However, females migrate to coastal waters to give birth during breeding seasons, so juveniles are usually coastal as well.

These sharks feed on smaller sea creatures such as fish, cuttlefish, lobsters and shrimp, as well as other sharks and rays. But it does not mean that the mighty and the puny are rivals. In fact, nature has a way of pairing unlikely animals as partners.

Parasites that pester the powerful sharks can actually be a feast for smaller fishes. These cleaner fish cluster to form "cleaning stations" in the sea, which the scalloped hammerhead sharks often visit to have parasites picked off their skin, gills and mouths. In this way, a mutually beneficial relationship is formed.

Despite the ecological significance of scalloped hammerhead sharks, they are, unfortunately, threatened around the world. This species is listed as "critically endangered" on the International Union for Conservation of Nature Red List and in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, which stated that the international trade of the species must be strictly regulated to prevent their extinction.

Yet, the sharks' populations are still on a steep decline worldwide. They have been caught globally as target and bycatch, with their meat, liver oil, skin, cartilage and jaws harvested. But most of all, their fins are much sought after: hammerhead sharks are among the main shark species in the fin trade and one of the preferred species for shark's fin soup.

As a change agent of the conservation community, Ocean Park removed shark's fins from its menu 25 years ago. Since 2009, the park has been offering sustainable seafood dishes to visitors.

By 2015, a corporate sustainable seafood policy was in place and only sustainably-sourced seafood is used in Ocean Park's restaurants and food kiosks.

One great example of Ocean Park's efforts is the reinvention of fish balls and fish dumplings, Hong Kong's signature street food, that are available at the park by using sustainable fish sources certified by the Marine Stewardship Council.

Perhaps this too is an evolutionary step reflecting the adaptations that we should all make. So, are you willing to make a commitment to protect the sharks?

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