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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

How do Sharks Grow?

How do Sharks Grow?

Over the years I have been asked all sorts of questions about sharks, covering a broad range of pretty much everything, from; “Do sharks fart?” to “How do sharks grow?”

Let’s start with the latter, this was asked by an Ecologist friend; Heather Lyons, and is a particular favourite of mine, not least because the answer takes you on a journey of discovery on both a physiological and evolutionary level.

Read more here: https://biomeecology.com/marine-biology/2019/11/how-do-sharks-grow/

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

Stars in their eyes (well, skin).

Stars in their eyes (well, skin).

“Tonight Matthew i’m going to be…..” OK, enough of the British TV show references (of a particular era)! I actually want to talk about Smooth-hound sharks, Starry Smooth-hound identification to be exact (Mustelus asterias).

Easily observed spots or ‘stars’ on the dorsal side of Mustelus asterias

Recently i was given a box of trawl captured smooth-hound sharks from a local fish wholesaler for fecundity research as well as for ‘shark school’ my outreach programme. These sharks had been caught in the North Sea and upon initial external inspection provide a perfect example of how difficult it is to separate the Common Smooth-hound (Mustelus mustelus) from the Starry (M. asterias), when the white spots are used as the principal method of distinguishing between species (as they often are).

Obvious spots and a complete absence of them in 2 individuals of the same species; M. asterias

As you can see from the above photo, white spots can be clear or absent as well as feint, in individuals of the same species. Thus, spots are a poor taxonomic indicator. Differences in other external characteristics can be employed including; fin position and morphological characteristics of dermal denticles. However these can also be ambiguous, with the only definitive method of discrimination being the differences between their forms of viviparity (reproductive methods). The common smooth-hounds develop a placental connection with the mother through the interaction of the yolk sac, egg envelope and uterine wall whereas the Starry have no physical connection to the mother and rely on the yolk sac during early stages of development. Of course this is simply not a practical method for live animals and is obviously no use for males.

M. asterias with obvious star patterning

A study by Farrell et al back in 2009, developed a genetic identification method to distinguish between mustelus and asterias. During that study samples were collected from 431 animals caught in the North East Atlantic, the Irish Sea, the Celtic Sea, the Bristol Channel and the North Sea. Of these 43 had been visually identified as mustelus species. However genetic analyses proved that in fact ALL of these individuals were in fact asterias. So, if you see a smooth-hound around the British coastline be it with or without those stars, it’s pretty reasonable to assume you’re looking at a Starry Smooth-hound Mustelus asterias.

Posted by Lauren Smith on

Egg(case) Hunting this Easter

Egg(case) Hunting this Easter

Are you heading to the beach this Easter? If so forget the chocolate eggs – shark & skate eggcases are where its at!

A small spotted catshark (Scyliorhinus canicula), on Rattray Head beach, Peterhead, UK.

Some species of sharks and skates found around the UK coastline lay eggcases, this is a method of reproduction known as ‘oviparity’. Skates will lay their eggs on the seabed, with sharks usually attaching their eggs to nearby seaweed and kelp. Once the skate or shark pup has hatched, the eggcases often wash-up on the shoreline due to rough seas, or simply as a result of tidal currents and prevailing wind directions.

Some of the eggcases we have found around the Scottish coastline, Top L-R: Flapper, Blonde, Spotted, Thornback, Cuckoo and Starry Skate. Bottom L-R: Bull Huss and Small Spotted Catshark.

The Shark Trust has a number of useful guides online for identifying and recording your eggcase finds, so check out their website for more information. And don’t forget to report your finds to them (they have an app available for this too) – adding important data to their ‘great eggcase hunt’ which is a good indicator of species and populations of skates and sharks in nearby waters. Of course we would also love to see your finds, so tag us in your finds @saltwaterlifeuk on Insta and Twitter and @sharkiologist for our Facebook Page.

Resources provided online by The Shark Trust, check out what they have by going to www.sharktrust.org

Remember to check that your eggcase is empty, if in any doubt return it to the water!

Happy Eggcase Hunting!