Allen To and Vivian Lam investigate shark fishery in the South China Sea and reflect on the current status and trends of shark populations in the region.

Since the 1970s and thanks to Steven Spielberg, the world has got the most stunning and probably the most unforgettable impression on sharks. The image of the bloody sea and screaming crowds definitely etched into everyone’s minds. Second only to the outdated Lamarck’s illusion that marine resources are inexhaustible, sharks are grossly mistaken as an invincible, ferocious top predator of the oceans.

Misunderstood Creatures

In the face of declining commercial fisheries worldwide, it may prompt one to wonder if these mighty predators can survive this global fishery crisis. Using a case study from Hong Kong and field visits to several fish markets in the region, let’s explore the possible future of sharks in South China Sea. But before we start our fishy journey, let’s go to the basics – the general biology of sharks. For the sake for clarity, the term ‘shark’ is used to refer collectively to sharks, skates, rays and chimaeras, which are all under the same taxonomic group, class Chondrichthyes.

Sharks are carnivorous top predators. They eat meat, basically fishes and molluscs but some feed on mammals and birds. Unlike many fishes we normally come across, sharks do not have hard bones; instead they use cartilages as supporting structure in the body (that’s also why we hardly get whole shark fossils!). Sharks have roved the ocean for hundreds of millions of years and have remained relatively unchanged throughout the period. Many species are about a metre big but some like the whale shark can grow beyond 10 metres.

Being ancient and successful predators, many have evolved into the lifestyle of being slow-growing, having late maturation and giving birth to few newborns. These biological characteristics render many sharks vulnerable to high fishing pressure. Simply put, sharks are removed faster than they can naturally replenish themselves.

So what about sharks in the northern South China Sea? The answer to this question is neither easy nor straightforward. Despite the popularity of utilising shark meat, fins, liver oil and jaws for different purposes, fishery data in the region are lacking or incomplete for sharks.

One of the biggest problems with shark fishery data, if available, is that information is lumped under a big category named sharks, hence not specie specific. With different sharks having different biological characteristics, this data is hardly sufficient for the monitoring of our sharks in the region. The use of anecdotal information, unpublished literature and interviews with experienced fishermen can help us understand better about the past of shark fishery, upon which present-day fishery status can be compared with. Instead of telling you the global status of sharks, let’s journey into Hong Kong, China, to have a brief look on the change in shark fishery over the past several decades.

Shark Fishing Since the Sixties

The 1960s to 1980s marked the peak shark landing period for Hong Kong with more than a thousand metric tonnes landed annually. Shark meat, liver, fins were used and a most interesting find - skins of some species were dried and used as tool for cleaning pots and pans!

During that period, some 50 vessels were actively catching sharks. Shark fishing was practised throughout the year but catches were highly variable. Nonetheless, good catches were usually guaranteed; fishermen deploying long-lines often returned with several dozens of sharks. Many shark species were caught during that peak period but the most common species included the spottail shark, green shark, blacktip shark and several species of hammerhead shark, which are relatively large species.

The shark fishery collapsed towards the end of the 1980s. Catches have significantly declined over the years, fishermen that formerly targeted shark species gradually changed their targets to other fish species and commonly-caught sharks showed marked decline in sizes and weights compared to 10 to 20 years ago. The decline was so substantial to the point that targeted fishery on sharks no longer exists in Hong Kong. Mirroring other fishery resources, sharks are considered overfished. Sharks that turn up in the local food fish markets nowadays are bycatches, consist of few species and mainly small sized sharks such as the white-spotted bamboo shark. It is relatively docile and was outnumbered by other shark species in past fisheries. The ‘dark age’ of sharks has arrived.

Shark’s Place in an Ecosystem

So sharks are disappearing. But why should we bother? We can shift our menu after all! There is no easy answer to the potential effect of reduction in shark abundance. The interacting nature of the ecosystem means that even the most sophisticated study might not give full account on its consequence. Available evidence however indicates a potential cascading effect of shark removal from the ecosystem, notably a change to smaller shark species in the ecosystem, as their bigger competitors are first to be wiped out.

Population of smaller sharks such as rays, which feed on scallops, increased and this led to the decline of the scallop fisheries in southeastern U.S. (Myers et al. 2007). A modeling study even suggested that the removal of tiger shark may cause a rapid crash in the abundance of tunas and jacks (Stevens et al. 2000). This might occur as seabirds, which are prey to the tiger shark, proliferate after shark removal and these birds feed on juveniles of tunas and jacks. Evidence may not be enough to postulate possible consequence, but the ecosystem is going to undergo dramatic changes with the demise of sharks in our ocean and we are to bear the brunt if this happens.

Can we help? Definitely. Like never before, all of us have the biggest power in our hands to change the future of sharks – consumer power. The main driving force to shark fisheries comes from the demand for shark meat and fins. While the taste, texture and the suggested medicinal use of shark components remain subjective, it is no doubt that sharks around the world are in great trouble. Now that we recognise the problem, we have also the possible solution.

It is time to act, we urge you to stick to no-shark menus when dining out and attending banquets. As the next U.S. President Barack Obama put it – ‘change we can believe in’.

Photos by Allen To and Vivian Lam. Next month: The plight of sharks in China by Allen To and Vivian Lam

References

Myers, R., Baum, J.K., Shepherd, T.D., Powers, S.P. and Peterson, C.H. (2007) Cascading effects of the loss of apex predatory sharks from a coastal ocean. Science 315. 1846–1850.

Stevens, J.D., Bonfil, R., Dulvy, N.K. and Walker, P.A. (2000) The effects of fishing on sharks, ray, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science 57, 476 – 494.