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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

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

Call of the Blue

Call of the Blue

On the 19th of November i headed down to the Natural History Museum in London, i was attending a book launch party and would be doing a Q&A session on sharks whilst there. The book by Philip Hamilton is entitled “Call of the Blue” and tells the story of positive, focused people who are working to save our oceans. Featuring incredible images captured by Philip over a 5 year period, with chapters outlining the efforts by individuals and communities to inspire and drive change.

I was absolutely honoured to be a part of this, having been contacted around 18 months ago by Tom Hooper to give an interview about my work with sharks, excerpts of which were to be featured in the book. The launch was fantastic, representatives from all sectors were present, including CEO’s from huge companies, marine charities, activists and researchers like myself. All were there to understand more about our marine environment and the threats it currently faces.

In the afternoon prior to the launch party, the head curator of the fisheries department James Maclaine, was kind enough to indulge my curiosity and gave me a behind the scenes tour of the preserved elasmobranch specimens that were kept in the archives. This was absolutely fascinating and a real treat to see the scale of the collections they had, highlights included a Greenland Shark (Somniosus microcephalis), that had washed up on the UK coastline. This species is in my opinion one of the most extraordinary sharks out there, recent research using radio carbon dating techniques have been used on the eye tissue of these sharks. Results revealed that of the sharks sampled, age ranges varied with the minimum age being AT LEAST 272 YEARS OLD! The 2 largest sharks in the study were estimated to be between 335-392 years old! 

Having recently collected a number of eggcases around the Scottish coastline, i was particularly looking forward to seeing what species of eggcases were in the NHM collection. I was not disappointed! I was delighted (and a little concerned that i would drop it) when James handed me a Chimaera eggcase collected in 1904.

Equally fascinating was the enormous Great White Shark jaw, it was donated in the 1800’s to the museum and since then there has been an enormous amount of speculation as to the size of the shark that this jaw belonged to. Some scientists believe that the shark would have been around 8m!!! The stuff dreams are made of – well my dreams at any rate!

 

Posted by Lauren Smith on

Beach cleans & shark guts… it’s all rubbish

Beach cleans & shark guts… it’s all rubbish

Alongside my work as a shark biologist, I am a volunteer for the charity Surfers Against Sewage. As part of this role I organise and participate in numerous beach cleans along the U.K. coastline, more often than not the bulk of rubbish that we remove during these cleans are plastic items. Now assuming you haven’t been marooned in outer space in recent years, you will be well aware of the mounting plastic crisis and the fact that particles of plastic can be found in just about everything, from the air we breathe to the water and food we consume.

The ingestion of plastic debris by marine animals has been documented across a variety of species

including; marine mammals, sea birds, sea turtles and some fish species. However fewer reports have described ingestion by sharks, and so for me it was a logical step to investigate whether a small shark species, commonly landed in the U.K. contained plastics. The small spotted catshark, more often referred to as the lesser spotted dogfish (cats… dogs… for the record they are catsharks, dogfish refer to another type of shark species), are often caught in bottom trawls and line gear, although technically bycatch the larger individuals are retained for human consumption, whilst the smaller ones are used for fish meal or pot bait.

I contacted a local fish merchant based in Fraserburgh on the Moray Firth Scotland, they kindly donated 20 sharks that had been captured in the North Sea and I set about investigating the contents of their gastrointestinal tracts, a polite way of saying I dug about and scrutinised their guts, recording any identifiable objects both natural and artificial.

Of the 20 sharks i sampled, all showed evidence of predation on natural prey sources prior to being trawl captured. Remains of hermit crab carapaces, squid beaks and fish bones were found. In addition to this 3 individuals were also found to contain plastic debris within their stomachs, one is a microplastic (defined as any particle less than 5mm) believed to be a micro-bead, the other two are macroplastics (>20mm); one is thought to be a broken and eroded tag and the other is composed of three fibres most likely originating as synthetic rope.

S. canicula are known to be opportunistic feeders that predate on a wide range of fauna, including shellfish, crabs, squid and small fish. It is unclear as to whether the plastics found within the stomachs of S. canicula had been ingested directly from the water column itself, or whether these items had been previously consumed by their prey. It remains unknown for now as to whether the ingestion of these plastics will negatively impact the individual sharks, however recent studies show that the potential effects on marine species from the uptake of microplastics include; reduced survival, inability to predate effectively, oxidative status and uptake of persistent organic pollutants. Current research is now investigating the effects of biomagnification and bioaccumulation of plastics and associated chemicals throughout freshwater and marine ecosystems.

S. canicula are considered an abundant shark species with an IUCN (International Union for the Conservation Nature) Red List status of “least concern”and yet with increasing environmental threats such as plastic ingestion, combined with the overfishing of other species, resulting in these sharks being used as market substitutes, it remains to be seen for how long this status will hold true.

My study reports the first evidence of plastic debris in the stomach of S. canicula, and yet I wasn’t surprised, heck I expected to find some evidence of plastics I just wasn’t sure how much. If this isn’t depressing and a sign of our times I don’t know what is. But with recent reports detailing that an estimated 75% of all the litter in our oceans is plastic, and with around 5 million tonnes of plastic waste entering the seas annually (Thompson, 2017), its no wonder I am not surprised only saddened that I am finding plastic in the guts of sharks.

What’s the link between beach cleans and shark guts?

Alongside my work as a shark biologist, I am a volunteer for the charity Surfers Against Sewage. As part of this role I organise and participate in numerous beach cleans along the U.K. coastline, more often than not the bulk of rubbish that we remove during these cleans are plastic items. Now assuming you haven’t been marooned in outer space in recent years, you will be well aware of the mounting plastic crisis and the fact that particles of plastic can be found in just about everything, from the air we breathe to the water and food we consume.

The ingestion of plastic debris by marine animals has been documented across a variety of species

including; marine mammals, sea birds, sea turtles and some fish species. However fewer reports have described ingestion by sharks, and so for me it was a logical step to investigate whether a small shark species, commonly landed in the U.K. contained plastics. The small spotted catshark, more often referred to as the lesser spotted dogfish (cats… dogs… for the record they are catsharks, dogfish refer to another type of shark species), are often caught in bottom trawls and line gear, although technically bycatch the larger individuals are retained for human consumption, whilst the smaller ones are used for fish meal or pot bait.

I contacted a local fish merchant based in Fraserburgh on the Moray Firth Scotland, they kindly donated 20 sharks that had been captured in the North Sea and I set about investigating the contents of their gastrointestinal tracts, a polite way of saying I dug about and scrutinised their guts, recording any identifiable objects both natural and artificial.

Of the 20 sharks i sampled, all showed evidence of predation on natural prey sources

prior to being trawl captured. Remains of hermit crab carapaces, squid beaks and fish bones were found. In addition to this 3 individuals were also found to contain plastic debris within their stomachs, one is a microplastic (defined as any particle less than 5mm) believed to be a micro-bead, the other two are macroplastics (>20mm); one is thought to be a broken and eroded tag and the other is composed of three fibres most likely originating as synthetic rope.

S. canicula are known to be opportunistic feeders that predate on a wide range of fauna, including shellfish, crabs, squid and small fish. It is unclear as to whether the plastics found within the stomachs of S. canicula had been ingested directly from the water column itself, or whether these items had been previously consumed by their prey. It remains unknown for now as to whether the ingestion of these plastics will negatively impact the individual sharks, however recent studies show that the potential effects on marine species from the uptake of microplastics include; reduced survival, inability to predate effectively, oxidative status and uptake of persistent organic pollutants. Current research is now investigating the effects of biomagnification and bioaccumulation of plastics and associated chemicals throughout freshwater and marine ecosystems.

S. canicula are considered an abundant shark species with an IUCN (International Union for the Conservation Nature) Red List status of “least concern”and yet with increasing environmental threats such as plastic ingestion, combined with the overfishing of other species, resulting in these sharks being used as market substitutes, it remains to be seen for how long this status will hold true.

My study reports the first evidence of plastic debris in the stomach of S. canicula, and yet I wasn’t surprised, heck I expected to find some evidence of plastics I just wasn’t sure how much. If this isn’t depressing and a sign of our times I don’t know what is. But with recent reports detailing that an estimated 75% of all the litter in our oceans is plastic, and with around 5 million tonnes of plastic waste entering the seas annually (Thompson, 2017), its no wonder I am not surprised only saddened that I am finding plastic in the guts of sharks.

Having visited 25 beaches in the past 6 months, along the U.K., French, Spanish & Portuguese coastlines and having found plastics on every single one of those beaches the consequences of our plastic mania will be felt far into the future. However the current wave of awareness about plastic pollution amongst the general public is encouraging, the more information and education that is provided via environmental charities such as Surfers Against Sewage and through TV Shows like Blue Planet 2 as well as on social media, will create positive change by allowing people not only to make more informed choices but also to lobby and campaign to bring about change, that is so desperately required.

References

Avio, C.J., Gorbi, S., Regoli, F., 2017. Plastics and microplastics in the oceans: From emerging

pollutants to emerged threats. Marine environmental research. 1-10.

Colmenero, A.I., Barria, C., Broglio, E., Garcia-Barcelona, S., 2017. Plastic debris straps on threatened blue shark Prionace glauca. Marine Pollution Bulletin. 115, 436-438.

Derraik, J.G.B., 2002. The pollution of the marine environment by plastic debris: a review. Marine

Pollution Bulletin. 44 (9), 842-852.

Mallory, M.L., 2008. Marine plastic debris in northern fulmars from the Canadian high Arctic. Marine Pollution Bulletin. 56, 1501-1504.

Putnam, A.R., Clune, A., Buksa, B., Hammer, C., VanBrockin, H., 2017. Microplastic biomagnification in Invertebrates, Fish and Cormorants in Lake Champlain. Centre for Earth and Environmental

Science. 37.

Smith, L.E., 2018. Plastic ingestion by Scyliorhinus canicula trawl captured in the North Sea. Marine Pollution Bulletin. 130. 6-7.

Thompson, R., 2017. A journey on plastic seas. Nature. 547, 278-279.