Securing a better future for hammerhead sharks

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Sharks are fast disappearing from the world’s oceans, mainly due to overfishing. Despite being dreaded by some, one cannot help but admit that they are extraordinary animals. As both large and small-scale fishermen in Sri Lanka poach them for export and subsistence, immediate action is needed to secure a better tomorrow for them. Concerns have been raised about the future of hammerhead sharks, particularly the Great and Scalloped Hammerhead sharks, which are now classified as critically endangered. 

Environmental Lawyer, Dr. Jagath Gunawardana said two of the four species of hammerhead shark found in Sri Lanka, mainly the Great Hammerhead and the Scalloped Hammerhead, are classified as critically endangered in the IUCN Red List of Threatened Species.

“It is necessary for Sri Lanka to place certain restrictions on the killing of hammerhead sharks to protect these two endangered species within its waters. This can be done under the provisions of two laws in Sri Lanka. One is to place them under the protected category under Section 31(A) of the Fauna and Flora Protection Ordinance. This does not require the Act to be amended by another Act of Parliament,” he said.

Speaking further, he said the second option is to protect them under Section 29 of the Fisheries and Aquatic Resources Act by order of the Fisheries Minister. If needed, both of these can be done simultaneously.

“These unique animals are not well known in Sri Lanka and it may be a reason why they have not received the attention they deserve,” he added.

Scalloped Hammerhead (Sphyrna lewini)

Scalloped Hammerhead has most recently been assessed for The IUCN Red List of Threatened Species in 2018. Sphyrna lewini is listed as Critically Endangered under criteria A2bd.

According to the IUCN, the Scalloped Hammerhead (Sphyrna lewini) is a large (up to 420 cm total length) coastal and semi-oceanic pelagic shark that is circumglobal in warm-temperate and tropical seas, from the surface and intertidal zone to depths of 1,043 m.

The global population structure varies between males and females; males move across ocean basins, while females only move regionally. The species is caught globally as target and bycatch in pelagic commercial and small-scale longline, purse seine, and gillnet fisheries, and is retained for the meat and fins. The Scalloped Hammerhead has declined sharply in all oceans, with some signs of stabilisation and possible recovery in response to management only in the Northwest Atlantic and Gulf of Mexico. The weighted global population trend estimated median reductions of 76.9–97.3 per cent, with the highest probability of >80 per cent reduction over three generation lengths (72.3 years), and is therefore assessed as Critically Endangered A2bd.

Threats posed to Scalloped Hammerhead

The IUCN Red List of Threatened Species also showed that the Scalloped Hammerhead is caught globally as target and bycatch in commercial and small-scale pelagic longline, purse seine, and gillnet fisheries. Most of the catch is taken as bycatch of industrial pelagic fleets in offshore and high-seas waters. It is also captured in coastal longlines, gillnets, trammel nets, and sometimes trawls, particularly in areas with narrow continental shelves. The species is also taken in beach protection programmes that target large sharks.

The species is generally retained for the meat and fins, unless regulations prohibit retention. Under-reporting of catches in pelagic and domestic fisheries is likely. The species has high at-vessel mortality of 57.1 per cent on Portuguese longlines in the Atlantic, 62.9 per cent on United States shark bottom longlines, and 71.4 per cent for Western Australian demersal longlines. The post-release mortality is higher for injured released sharks and has been reported as 100 per cent for the Scalloped Hammerhead in purse seines.

Great Hammerhead (Sphyrna mokarran)

Great Hammerhead has most recently been assessed for The IUCN Red List of Threatened Species in 2018. Sphyrna mokarran is listed as Critically Endangered under criteria A2bd.

IUCN highlighted that the Great Hammerhead is a generally solitary, coastal, and semi-oceanic pelagic shark, that occurs close inshore and well offshore at depths ranging from near-surface to 300 m deep. The maximum size is reported as 550 to 610 cm total length (TL) according to Compagno (1984), though 400 cm TL is a more commonly observed maximum size. Males mature at 225-269 cm TL and females mature at 210-300 cm TL. Reproduction is aplacental viviparous, with litter size of 6-42 pups, a gestation time of 11 months, a likely biennial reproductive cycle, and a size at birth of 50-70 cm TL. There is regional variation in age estimates; female age at maturity is 5.5 and 8.3 years and maximum age is 44 and 39 years; generation length is therefore 24.8 and 23.7 years in Northwest Atlantic and Western Central Pacific, respectively. Population growth rate estimate is 0.07 per year.

Threats posed to Great Hammerhead

The Great Hammerhead is caught globally as target and bycatch in commercial and small-scale pelagic longline, purse seine, and gillnet fisheries. It is also captured in coastal longlines, gillnets, trammel nets and sometimes trawls, particularly in areas with narrow continental shelves. The species is often retained for the fins, unless regulations prohibit retention. Under-reporting of catches in pelagic and domestic fisheries is likely. At-vessel mortality is estimated as 56 per cent on US shark bottom longlines and 30.8 per cent on Western Australia demersal longlines. The post-release mortality is higher for injured released sharks and has been reported as 100 per cent for the closely-related Scalloped Hammerhead in purse seines. The species is taken in beach protection programmes that target large sharks, according to IUCN.

‘Not illegal yet’

Scalloped and Great Hammerhead fishing is lawful, according to Deputy Director at the Department of Fisheries and Aquatic Resources, Sandamali Herath.

According to her, the department has so far safeguarded three species of thresher sharks.

“Another reality is that our fishermen have caught some sharks. Because only a few fishermen catch sharks for their livelihood, we still have not made a decision to safeguard them. In contrast to other countries, all shark flesh is consumed by the people of Sri Lanka and is a low source of protein,” she pointed out. She added that sharks are caught for food as well as for their fins. “The majority of sharks are caught accidentally. Therefore, it is presently allowed to catch sharks,” she said.

Export licence 

National Aquatic Resources Research and Development Agency (NARA) Scientist, Thejani Balawardhana said, as the two species fall under criteria A2bd, poaching is not illegal.

However, she said in order to export the fins of these critically endangered sharks, exporters are required to obtain a licence from the Department of Wildlife Conservation.

“We do not have any particular restrictions in place for them. When the shark fins are exported, permission should be obtained, as they fall within criteria A2bd. Apart from that, we gather information about these sharks. But to this date, no laws have been put in place based on that evidence,” she said.

Five species are forbidden at present, but there are no laws regulating these species. There is insufficient data to make an informed decision. Therefore, we need to gather more data to implement rules and regulations, she explained.

By Thameenah Razeek