The importance of sharks?
As apex predators, sharks play an important role in the ecosystem and also serve as an indicator for ocean health. Sharks help regulate abundances of species by removing the weak and the sick. Sharks also help maintain the balance with competitors to ensure species diversity. The role of sharks in the food chain also indirectly affects commercial fisheries and our economy. The dramatic decline of sharks caused an increase in cownose rays, which led to a decline in scallops (prey of rays) and subsequently the closure of the bay scallop fishery in North Carolina.
Whale shark, the gentle giant
One of the most charismatic and well-known shark species, whale shark feeds on plankton despite being the largest fish on Earth. Whale sharks travel long distances and can be found in tropical and warm temperate waters. Threatened by target fisheries, bycatch in nets and vessel strikes, whale sharks are now listed as â€œEndangeredâ€ on the IUCN Red List of Threatened Species, uplisted from â€œVulnerableâ€ in 2016. Whale sharks are moving one step closer to extinction and it is hoped that the uplisting can facilitate the implementation of protection measures at national levels.
Researchers can identify different individuals based on the spots and stripes behind the left pectoral fin as the patterns are unique. As a citizen, you too can assist with whale shark research, by submitting photos and sighting data. The Wildbook for Whale Sharks photo-identification library
is a visual database of whale shark encounters and of individually catalogued whale sharks. The library is maintained and used by marine biologists to collect and analyse whale shark sighting data, e.g. distribution and population. The information you submit will be used in mark-recapture studies to contribute to the global conservation of this threatened species.
Whale sharks are not commonly found in Hong Kong, but sightings have been recorded in the months of June to July in 2008, 2010, 2012 and 2015. If you are lucky enough to see one, please observe it at a distance and follow the no touching and feeding regulation. If you are planning to participate in whale shark interaction programmes overseas, do pay attention to the operational impacts on the well-being of whale sharks and the local community and opt for good ecotourism operators that comply with whale shark interaction regulations.
Response for stranding of sharks and rays in Hong Kong
Building on the 10-year collaboration on handling marine mammal stranding cases in Hong Kong waters, OPCFHK and Agriculture, Fisheries and Conservation Department (AFCD) have expanded the stranding response programme to collaborate, investigate and respond to strandings of selected threatened species of sharks and rays in Hong Kong waters in June 2016. The species are selected based on their IUCN Red List status and includes shark species which are classified as â€œVulnerableâ€, â€œEndangeredâ€ or â€œCritically Endangeredâ€.
Pacific spadenose shark â€“ Hong Kongâ€™s resident shark
On June 23, 2016, a shark stranding case that occurred at Butterfly Beach, Tuen Mun was brought to AFCD, and then OPCFHK for investigation. The individual is a Pacific spadenose shark (Scoliodon macrorhynchos
), one of the resident shark species in Hong Kong waters. The carcass was sent to Ocean Park for a necropsy by the Stranding Response Team for further examination. Measuring 61cm and weighing only 0.82 kg, the adult female shark has no external wounds but the body was moderately decomposed (code 3). The cause of death cannot be determined.
Pacific spadenose shark usually occurs in shallow, inshore tropical waters and is abundant near large fresh-water outflows (e.g. Pearl River Estuary). The species grows to a maximum length of about 70 cm and reaches sexual maturity at around 50 cm for both sexes. Pacific spadenose shark is not evaluated on the IUCN red list and is harmless to humans.
Most shark species found in Hong Kong do not pose threats to humans unless provoked. Please call the 1823 hotline to inform AFCD if sharks are sighted. If you encounter a shark during recreation, you are advised to stay calm and slowly swim away from the shark. Report the incident to AFCD and lifeguards on duty if you are at gazetted public beaches. Please bear in mind that you are safe if you swim within the shark net area, and in most occasions, sharks would not attack if they are not provoked.
Shortfin mako shark - first official record in Hong Kong
On February 4, 2017, OPCFHK responded to a code 4 shark stranding case on a beach in Mui Wo. The female shark measured 2.45 metres but due to severe decomposition, especially the fins, the species cannot be identified on-site. Subsequent DNA analysis confirmed that it is a shortfin mako shark (Isurus oxyrinchus)
, making it the first official record in Hong Kong. Shortfin mako is warm blooded and hence adaptable in both tropical and temperate waters. A female shortfin mako shark, tagged in New Zealand waters, travelled 8,265 miles in over six months, averaging 37 miles per day. Data indicated maximum speeds of 62 miles per hour in short bursts, likely when hunting fast-swimming prey.
Shortfin mako is an important target species for fisheries and recreational game fishing, and is often found caught as bycatch in tuna and billfish longline and driftnet fisheries, particularly in high-seas fisheries, making them vulnerable to extinction. For this particular shark found in Hong Kong, there was no evidence of propeller cuts or entanglement in fishing gear. Due to severe decomposition of the carcass, we were unable to determine the cause of death.