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Posted by Lauren Smith on

Shark DNA Zip-coding; a way to identify the origin of sharks caught for the international fin trade.

Shark DNA Zip-coding; a way to identify the origin of sharks caught for the international fin trade.

In February 2016 I was in Hong Kong looking into the shark fin trade, it was a couple of days before the Chinese New Year and there were fins everywhere, to suit all types of consumer. You could buy them in general food stores, pharmacies and fishing villages. You could buy small ones in plastic bags, multi-packs or single large ones with festive red bows tied around them.

I have written before about the origins of shark fin soup, however it is worth re-capping slightly: The cartilage in the fins is usually shredded and used primarily to provide texture and thickening to shark fin soup, a traditional Chinese soup or broth dating back to the Song Dynasty (960-1279). The dish is considered a luxury item embodying notions of hospitality, status and good fortune.

The origin of the dish can be traced to the Emperor Taizu of the Northern Song, who reigned from 960-976. It is said that he established shark fin soup to showcase his power, wealth and generosity. The dish’s popularity increased during the Ming Dynasty (1368-1644) as a result of an admiral of the imperial navy; Zheng He, who commanded expeditionary voyages around Asia and East Africa from 1405-1433, bringing back fins that fishermen had discarded. From this point onwards shark fin soup became an established dish and by the time of the Qing Dynasty (1644-1912) was in high demand.

It is not surprising that the popularity of a dish embodying such aristocracy and elitism declined once the Chinese Communist Party came to power in 1949. However, by the late 1980’s China had undergone far-reaching market-economy reforms which led to a rapidly expanding upper and middle class, who were eager to showcase their new-found wealth; shark fin soup once again became a way of doing so. Considering that the price per bowl can range from just HK$5 (45p) to an incredible HK$2000 (£180) depending on the type, style and preparation of the shark fin served, the dish is a viable option for a large number of people.

For fishermen operating within the global fin trade circumstances are different although all are motivated by a form of economic or socio-economic gain. Some large scale longlining operators see shark landings as a way to optimise their catch throughout the seasons, whereas with smaller-scale fisheries it is usually the prospect of short-term gain that initially entices them in. The price paid for the fins is higher than for their normal catch, yet they are paid relatively little when compared to the money made higher up the chain by the fin traders.

Hong Kong is an important trade hub and consumer of shark fins from shark fishermen operating globally. The main threat to shark populations remains overfishing, however the dried fin trade is undeniably a key driver of shark fishing, adding pressure to specific species and/or populations that are already at risk of extinction.

By using molecular genetics, the identification of shark species is possible even after fins have been removed. These techniques are the most reliable way to determine which species are the most heavily traded. However although this is useful, the species ID only gives us so much, for example some species specific populations are more at risk than others, for example globally the Porbeagle shark is classified as ‘Vulnerable’ by the IUCN (International Union for the Conservation of Nature), and yet the North East Atlantic population is ‘Critically Endangered’.

Thankfully a new scientific study has just been published by Fields et al. in the journal ‘Animal Conservation’ which has the potential to revolutionize our understanding of global shark trade dynamics and provide critical information required to effectively implement shark fisheries management and trade restrictions.

In their study the authors investigate the trade of the scalloped hammerhead, of which there is a mounting concern about their sustainability with an increased effort to assess their global status and establish management measures. Globally the species is listed as ‘Critically Endangered’ by the IUCN and in 2013 was listed on Appendix II of CITES (Convention on International Trade in Endangered Species). The latter requires permits issued by the exporting country certifying that products were legally and sustainably taken from the wild and traceable throughout the supply chain.

However as the study points out, there have been seizures of illegal scalloped hammerhead products at the border in Hong Kong and retail market surveys have provided evidence of substantial non-compliance in the early implementation of CITES for scalloped hammerheads and other listed species. Although globally listed as ‘Critically Endangered’, there is variation in the status of individual scalloped hammerhead populations. Molecular analyses has revealed significant global stock structure, with at least nine distinct regional populations described across the literature.

Therefore scalloped hammerhead shark populations thus experience different fishing pressures and extinction risk based on the region in which they are found, making it important to know the sources of scalloped hammerhead products in fin trade and consumption locations such as Hong Kong. Fisheries management can then be prioritized further upstream in the supply chain.

In order to determine which populations of a species is being exploited by a fishery, the study uses a method known as GSI (‘genetic stock identification’). This technique is based on the use of genetic markers that differentiate populations. Samples of fin trimmings (smaller, cheaper off-cuts from the fin trade) were taken from an unknown mixture of shark populations and then compared to a comprehensive genetic database of all populations of that species. This method is possible because scalloped hammerheads have been the subject of a comprehensive analysis of global population structure and a previous study provided proof-of-concept that GSI was possible for this species.

The results for this study by Fields et al found that the majority of scalloped hammerhead fin trimmings (61.4%) came from the Eastern Pacific population where this species is listed as ‘Endangered’. Overall six of the nine scalloped hammerhead populations were found in the fin samples, clearly indicating a near global sourcing of scalloped hammerhead fins in the Hong Kong market.

The authors point out that many coastal sharks exhibit population structures similar to scalloped hammerheads and therefore similar databases and GSI workflows could be applied to these species if investments in global phylogeographic studies and trade surveys are undertaken. Such an investment would greatly advance species and stock-specific management for sharks, which are urgently needed worldwide.

This is particularly poignant, considering the news that broke just a few days ago about the record 26-tonne seizure of illegal shark fins by Hong Kong customs officials, in consignments from Ecuador worth an estimated HK $8.6 million (US $2.4 million). Consisting of predominantly Thresher and Silky shark species, with an estimated excess of 38,000 sharks killed. Add this to the other nine shark fin smuggling consignments that have already been seized by customs over the past 4 months, then that’s 67 tonnes so far this year. How many more have slipped through unnoticed? How long can shark populations sustain these pressures?

Reference: Fields et al 2020. DNA Zip-coding: identifying the source populations supplying the international trade of a critically endangered coastal shark. Animal Conservation. https://doi.org/10.1111/acv.12585

Posted by Lauren Smith on

Two new species of saw sharks discovered

Two new species of saw sharks discovered

The newly discovered Pliotrema kajae and Pliotrema annae six-gill saw sharks, were discovered during research investigating small-scale fisheries operating off the coasts of Madagascar and Zanzibar. The discovery of these two new sharks highlights how little we still know about life in the ocean and the impact we are having on it.

Read more here: https://biomeecology.com/news/2020/04/two-new-species-of-saw-sharks-discovered/

Posted by Lauren Smith on

What is Biofluorescence? Shining a light on biofluorescence in UK waters.

What is Biofluorescence? Shining a light on biofluorescence in UK waters.

Biofluorescence is essentially the ability of an organism, to absorb electromagnetic wavelengths from the visible light spectrum by fluorescent compounds, and the subsequent emission of this at a lower energy level.

In this blog piece for the BiOME Ecology webzine i talk to plant pathologist James Lynott about this incredible phenomenon: https://biomeecology.com/news/2019/10/shining-a-light-on-shark-biofluorescence-dr-l-smith/

Posted by Lauren Smith on

In Search of a Plankton Feeder

In Search of a Plankton Feeder

A Basking Shark feeding on plankton. Photo Credit Richard Aspinall

The Basking Shark (Cetorhinus maximus) can reach lengths of up to 12m and is the largest shark in British waters and the second largest in the world after the Whale Shark. Both are plankton feeders, and it is the plankton rich water (primarily along the West Coast) during the spring and summer months which results in these giants visiting our shores.

Despite the basking shark belonging to the same family, as the great white shark (Lamniformes) it is in a genus of its own: Cetorhinidae. Of course being a plankton eater can make it rather more elusive than a great white and baiting it in is out of the question! However understanding more about how basking sharks feed and their prey certainly helps when trying to locate them in the Ocean. Dr Dave Sims and his team at the Plymouth Marine Laboratory have undertaken a substantial amount of work in this area;

Originally it was thought that basking sharks were indiscriminate filter feeders, engulfing whatever was suspended in front of them. However, Sims et al have shown that sharks elect to feed in waters which contain higher concentrations of their preferred prey species which happen to be planktonic shrimp. It is not known for certain how sharks actually locate high concentrations of these shrimp but there are currently a couple of theories. One theory is that sharks are capable of detecting the odour of dimethyl sulphide (DMS) emitted by phytoplankton when it is being grazed on by zooplankton. The second theory is that the sharks can detect activity of their prey using their electroreceptors known as Ampullae of Lorenzini.

Basking sharks feed at varying depths in the water column exploiting optimal food sources (deep sea shrimp have been found in their stomach contents). Sims et al reported that sharks do not feed when the plankton concentration is less than 1 gram of plankton per cubic meter of water, presumably because it is energetically not worthwhile. The higher the plankton concentration, the longer the sharks feed. When the plankton reach concentrations of 3 grams of per cubic meter of water the sharks will feed for up to two and a half times longer than when it’s at 1 gram. When they find a good place to feed they adopt a zigzag swimming pattern, this behaviour is termed “area restricted searching” or ARS. A preference for feeding occurs at current fronts where two water masses of different temperature meet. When the sea is calm less mixing occurs and the water stratifies into different layers, typically warmer on top, cooler below. This may result in the plankton experiencing low nutrient levels. Therefore plankton levels are higher where waters of different temperatures mix, such as at a thermal front. These fronts can be seen as almost slick lengths of still water and can be very useful for spotting sharks near the surface, these fronts can also collect quantities of debris such as jellyfish and seaweed which can make their identification even more obvious.

Basking sharks feed by a method known as obligate ram filter-feeding (Whale Sharks feed by a different technique known as suction feeding). They cruise along when feeding (typically around 1.9 miles per hour), with their mouth wide open, allowing the plankton rich water to pass through the gill slits where it is filtered out by gill rakers, near the rakers are cells which secrete large quantities of mucous when the shark closes its mouth (usually after 30-60 seconds), the rakers collapse squeezing the plankton mucous mixture into the mouth so it can be swallowed.

A large female Basking Shark (Cetorhinus maximus) with possible mating scars visible on her pectoral and pelvic fins. Photo credit: Richard Aspinall.

Many thanks to Richard Aspinall for the use of his images in this post.

References and Further Reading

Sims D.W. (1999) Threshold foraging behaviour of basking sharks on zooplankton: life on an energetic knife-edge? Proc. R.Soc.Lond. B.266:1437-1443.

Sims D.W.(2000) Filter-feeding and cruising speeds of basking sharks compared to optimal models: they filter-feed slower than predicted for their size. Jour. Exp. Mar. Biol. Ecol. 249: 65-76.

Sims D.W., Fox A.M. and Merret D.A. (1997) Basking shark occurrence off south-west England in relation to zooplankton abundance. J.Fish.Biol 51: 436-440.

Sims D.W. and Merret D.A. (1997) Determination of zooplankton characteristics in the presence of surface feeding basking sharks Cetorhinus maximus. Mar. Ecol. Prog. Ser. 158: 297-302.

Sims D.W. and Reid P.C. (2002) Congruent trends in long-term zooplankton decline in the north-east Atlantic and basking shark (Cetorhinus maximus) fishery catches off west Ireland. Fish. Oceanogr. 11:1: 59-63.

Sims D.W., Southall E.J., Richardson A.J., Reid P.C. and Metcalf J.D. (2003) Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation. Mar.Ecol.Prog.Ser 248: 187-196.

Sims D.W., Southall E.J., Quayle V.A. and Fox A.M. (2000) Annual social behaviour of basking sharks associated with coastal front areas. Proc.R. Soc. Lond B. 267: 1897-1904.

Sims D.W and Quayle V.A. (1998) Selective foraging behaviour of basking sharks on zooplankton on a small scale front. Nature: 393: 460-464.

www.manxbaskingsharkwatch.org

Posted by Lauren Smith on

Hammer-time!

Hammer-time!

What does Hannibal Lecter, Ernest Hemmingway and I have in common? A taste for fava beans and a nice Chianti? (Chianti – yes), renowned literary skill? (pah! If only!). The answer is in fact the islands of Bimini, Bahamas situated 50 miles off the coast of Florida, North & South Bimini are the smallest habitable islands in the Bahamas with a total area of 9-square-miles and just over 2000 inhabitants.

bimini

Hemmingway began visiting the islands in 1935 and spent time fishing and writing, whilst angling he garnered knowledge which contributed to the creation of Old Man and the Sea and Islands in the Stream. An Atlantic Blue Marlin caught off Bimini weighing in at 500lbs was allegedly the inspiration behind these novels.

The final scene of Silence of the Lambs see’s Dr Lecter calling Agent Starling from a payphone on a tropical island, that island being North Bimini.

bimini customs

So what is it about Bimini that resulted in my visit, or to be more precise – my return visit? I had first gone to Bimini when I was conducting research for my PhD in 2006, I was staying at the Bimini Biological field Station (Shark-Lab) founded by “Doc” Gruber and was tracking juvenile Lemon Sharks and investigating their depth utilization.

Bimini is a well known Lemon Shark nursery area first recorded by Doc in the 1980’s, however in addition to the Lemon Sharks the Bimini Islands are a marine biologists and even more so a shark biologists dream, in shallow, clear waters you can see Nurse, Blacknose, Blacktip, Caribbean Reef, Tiger & Bull Sharks as well as Rays, Sawfish and the reason for my trip this time, the Great Hammerhead (Sphyrna mokarran).

hammer 2

There has been talk of Great Hammerheads visiting the waters around Bimini from January through to March for decades, and long is the legend of South Bimini Islands “Harbour Master” a huge Hammerhead patrolling the docks for fishermen’s scraps. However it has only been the last few years that the area has emerged into the main stream and has become recognised as the place to dive with aggregations of Great Hammerheads.

hammer 3

I was there with Dr Craig O’Connell founder of O’Seas Conservation foundation and his team (Guido Leurs founder of Oceaware, Marcella Uchoa and Rachel Jacobson), I had first met Craig on my initial visit to Bimini and having kept in touch and collaborated on a research paper together it was a fitting place to catch up in person! We has rented a boat and were observing and photographing animals in situ by freediving and SCUBA diving.

2 hammer

Put simply, my dives with the Hammerheads blew me away!! Once the bait had gone in the water we were inundated with nurse sharks typically after only a couple of minutes, on average we only had to wait around 20 minutes until the unmistakable outline and approach of the Hammers were spotted from the boat, a speedy kitting up and grabbing of camera equipment ensued (with a quick nod to the O’ring gods) and we descended down to the white sand with depths around 6m. Seeing these animals up close in the water was incredible, I certainly don’t possess the vocabulary or the literary skill to do them justice, they are truly humbling and awesome.

socks

On each dive Hammers exhibited different behaviours and swimming patterns which allowed for some fantastic photography opportunities , unlike the more classic shark body shape the angles and form of the Great Hammerheads combined with the sunlight filtering through the water and the approach of the sharks created the potential for yet another different and interesting shot, the opportunities were endless!

hammer 4

Sphyrna mokarran is the largest species of hammerhead shark, capable of attaining a total length of just over 6m (20ft) with 4m being a more usual maximum length. They are unmistakable with the straightness of the front margin of their head combined with their enormous sickle shaped first dorsal fin, they are a coastal pelagic and semi-oceanic species, considered to be an opportunistic predator feeding on a variety of prey including; stingrays and other batoids, small shark species, groupers, toadfish, jacks, crabs and squid etc. Males reach maturity around 2.5m and females around 3m, females breed every 2 years and have an 11 month gestation period (they are viviparous – pups nourished with a yolk sac placenta), litter size ranges from 6-42.

S. mokarran is classified as endangered by the IUCN Red List with a declining population trend, animals are taken as by-catch and as a target species in longline, fixed bottom net, hook & line, and pelagic and bottom trawl fisheries. Their fins are highly prized for shark-fin soup. These fishing pressures coupled with the Great hammerheads size at maturity and low fecundity make it extremely vulnerable, global population declines range from 79-90% in the last 25 years. In 2014 S. mokarran was listed on CITES Appendix II, which includes a list of species that are not necessarily now threatened with extinction but that may become so unless trade is closely controlled. International trade in specimens of Appendix II species may be authorized by the granting of an export permit or re-export certificate. No import permit is necessary for these species under CITES (although a permit is needed in some countries that have taken stricter measures than CITES requires). Permits or certificates should only be granted if the relevant authorities are satisfied that certain conditions are met, above all that trade will not be detrimental to the survival of the species in the wild.

On the subject of protection I worry about the future of Bimini and its marine wildlife, since I first visited the island 9 years a lot has changed. A Malaysian consortium (work originally began by “Bimini Bay Resort” but is now “Resorts World Bimini”) was granted approval to build a resort, casino, marina complex designed to attract 500,000 tourists a year, as a result mangrove habitats have been destroyed (essential shark nursery areas) and dredging of channels for cruise ships has taken place with the resulting repercussions on the coral reefs and critical habitats for other species such as lobster, grouper, and conch not to mention the natural storm protection for the island itself.

Bimini is a place with the power to turn dreams into a reality, my sincere hope is that people in positions of power will recognise the true beauty of Bimini and conserve it so that these Islands will never be referred to in the past tense, as a paradise lost….

 References and Further Reading;

http://www.iucnredlist.org/

http://www.bahamas4u.com/bimini.html

http://www.telegraph.co.uk/news/worldnews/centralamericaandthecaribbean/bahamas/10947445/Islands-In-The-Stream-The-battle-for-the-soul-of-Bimini.html

https://www.youtube.com/watch?v=Su5WKbaqbDA