Shark Research - Fisheries analysis reveals high shark bycatch in longline fisheries

A recent paper published in Marine Policy has carried out the first analysis of global elasmobranch bycatch patterns in commercial fisheries.

Bycatch - where species other than the intended target species are caught in a fishery - is a global problem. Many of today's commercial fishing methods, such as trawling or long lining, have few ways to ensure that only the intended species is caught.

By examining current fisheries data, the researchers assessed the quantity of elasmobranch bycatch across 4 commercial fishing methods: longlines, trawlers, purse-seines and gillnets. Of these 4 fishing methods, they found that pelagic longlines are responsible for the largest amount of shark bycatch - in fact in some instances the quantity of sharks caught in pelagic longline fisheries may exceed the intended catch. The majority of the shark bycatch was made up of blue shark (Prinace glauca) which is classified as Near Threatened in the IUCN Red List.

Long line fishing is a type of commercial fishing whereby a main line is laid out with hooks hanging off the line at intervals. Whilst longlines are intended to catch a target species - such as swordfish - the baited hooks also attract other species such as seabirds, turtles, other fish and sharks. Worse still, if fishing gear is discarded at sea the equipment can continue to catch and kill marine life - something known as ghost fishing.

This paper does not draw conclusions about the direct threat to sharks from these high levels of bycatch, but instead emphasises that the large numbers of sharks unintentionally caught and discarded by the commercial fishing industry is concerning and more research is required to understand if it is sustainable. The authors also highlight a need to implement management plans for elasmobranchs on a global scale.

 

 

Shark News - Megamouth Shark washes up in the Philippines

It seems as though all rarely sighted shark species are keen to make an appearance at the moment with a megamouth shark (Megachasma pelagios) washing ashore in the Philippines. This species is so rarely sighted that it is classified as Data Deficient in the IUCN Red List.

The 4.6m, male specimen was stranded on Pio Duran, Albay. Interestingly, this site is just a stones throw from Donsol - a natural aggregation site for whale sharks (Rhincodon typus). Like the whale shark, the megamouth shark is a filter feeder and could possibly have been attracted to the area by an abundance of Euphausiid shrimp - an important component of the diet of both the whale shark and the megamouth shark. In 2009 another megamouth shark was reported from Donsol, suggesting that this area could be frequented by these sharks. Megamouth sharks have been found at depths ranging from 5m to 4,600m and they may follow the diel vertical migration patterns of the Euphausiid shrimp - spending time at depth during the day and returning to the surface at night. This could explain why the sharks are so infrequently sighted. 

Photo courtesy of Marine Wildlife Watch of the Philippines. Photo credit Rosalina Sariola

This shark is thought to be circumglobal but a large number of sightings have been from Japan, Taiwan and the Philippines. The specimen has been nicknamed "Toothless" and has been stored on ice by the Bureau of Fisheries and Aquatic Resources (BFAR), Bicol to await a necropsy. 

Shark Research - Saudi Arabian Shark Fisheries not sustainable

A recent article published in Fisheries Research sheds light on our knowledge of shark fisheries in Saudi Arabia and indicates that these Red Sea fisheries are unsustainable.

The researchers, from King Abdullah University of Science & Technology (KAUST) and Woods Hole Oceanographic Institute, spent 2 years collecting samples from the Jeddah Fish Market (JFM) in the Kingdom of Saudi Arabia (KSA). During this time the team collected 2,724 individual samples across 37 species of elasmobranch. Seventy three per cent of the entire sample was made up of only 5 species: the spottail shark (Carcharhinus sorrah), the grey reef shark (C. amblyrhynchos), the silky shark (C. falciformis), the black tip shark (C. limbatus) and the milk shark (Rhizoprionodon acutus). Of these 5 species, 4 are classified as Near Threatened in the IUCN Red List.

Sharks for sale at the Jeddah Fish Market. Image from the daaamnblog

Perhaps most worryingly, the researchers discovered that a very large percentage (c. 81%) of the males caught had not yet reached sexual maturity. This is a cause for concern as if too many juveniles of a species are removed from a fish stock then the stock itself will be unable to replenish itself and will risk collapse.

The sharks were landed whole and whilst the fins were removed, this was done when the shark was back on land and the meat was then sold; however, the team noted that the cost of shark meat, compared to other fish, appeared to be very cheap in the KSA.

Whilst in many countries sharks may be considered more valuable alive than dead, owing to a boom in the eco tourism industry, the distinct lack of tourism in the KSA has not incentivised the government to implement and enforce policies regarding shark protection, despite the fact that the resources to carry out adequate shark management should not be unobtainable for the KSA.

Shark News - Rare Frilled Shark Caught in Australia

A lot of excitement seems to have been generated today by the capture of a frilled shark (Chlamydoselachus anguineus) off the coast of Victoria, Australia. The frilled shark is an incredibly rare species and one of only 2 in its genus (the other being the South African frilled shark Chlamydoselachus africana.)

Image from SETFIA http://www.setfia.org.au/item/living-fossil-captured.html

Don't worry though - despite the portrayal of this amazing species in most media stories as a "terrifying frilled shark from the deep", this shark isn't actually considered harmful to humans. For a start their principal diet consists of squid and crustaceans...and secondly they are a deep water species most commonly found at 500-1,000m.

Very little is known about this shark, which is why the South East Trawl Fishing Industry Association (SETFA) have reported that the animal was offered to the Commonwealth Scientific & Industrial Research Organisation (CSIRO) for data capture.

This animal has been classified as Near Threatened by the IUCN Red List as it is occasionally caught as bycatch - primarily by the bottom trawl and deep-set longline fisheries (which is why it is not overly surprising that this specimen was caught in trawler nets). There is concern that the frilled shark would be vulnerable if deepwater fisheries are expanded.

The frilled shark doesn't really have many close relatives still living today, but it is classified amongst the Hexanchiformes - an Order which includes several species of rare and wonderful shark such as the six gill and seven gill sharks. The frilled shark itself also has six gills making this group a little different from the rest of the sharks - most of which have 5 gills.

I wanted to include a nicer picture of a frilled shark rather than the - quite frankly unflattering one! - which has been attached to these news stories.

Image from Arkive http://www.arkive.org/frilled-shark/chlamydoselachus-anguineus/image-G38906.html

New whale shark aggregation site discovered off the coast of Saudi Arabia

A new whale shark (Rhincodon typus) aggregation site has been discovered off the coast of Saudi Arabia.

Prior to this study only 12 aggregation sites had been identified globally. The team - which brought together researchers from King Abdullah University of Science & Technology (KAUST) and marine organisations in Massachusettes - used satellite tags to track the movements of 47 whale sharks in the red sea between 2009 and 2011. They discovered that most of these sharks congregated on a single aggregation site in the Saudi Arabian red sea.

They also observed that approximately 10% of the tagged whale sharks left the red sea, indicating potential global interconnectivity between populations.

What is particularly notable about this aggregation site is that the population was equally distributed between males and females. In other know juvenile whale shark aggregation sites, males dominate. Still, very little information regarding whale shark sex segregation is known.

The discovery of this 13th site adds valuable insight into whale shark activity. As with most large, pelagic animals little is known of whale shark life history. Population estimates vary greatly, putting the number somewhere between 27,000 and 476,000 adults worldwide. The researchers also found that the tagged sharks spent very little time at the surface making frequent dives to 500m and as deep as 1360m; owing to the fact that the majority of whale shark observations and tagging have occurred at the surface our current data may greatly under-represent actual whale shark behaviour.

The researchers report that there are no known fishing efforts for whale sharks by either Saudi Arabia or Djibouti although as with all marine animals which stray too close to the surface they are vulnerable to ship strikes.

Growing up to 12meters in length, the whale shark is the largest known fish, and like most "marine giants" is a suspension feeder with a predominantly vegetarian diet.

Whale sharks are listed as Vulnerable in the IUCN Red List. Like most shark species they can sometimes be taken as bycatch of the fishing industry, often by entanglement in nets, and are vulnerable to poaching for their fins and oil rich livers. However, in many parts of the world whale sharks generate valuable income for the tourism industry as swimming with whale sharks has become a popular holiday experience; in these areas whale shark protection tends to be upheld as many countries see the benefits live whale sharks can bring.

This study adds new insight into whale shark populations in the red sea and lends support for putting in place conservation measures for this whale shark population.

Breumen, M., Braun, D., Cochran, J., Skomal, G. and Thorrold, S. (2014) Movement Patterns of Juvenile Whale Sharks Tagged at an Aggregation Site in the Red Sea. PLOSOne http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0103536

Shark Research - We may have sharks to thank for our pancreas!

A transcriptomic survey of the pancreas, brain and liver of the lesser spotted catshark (Scyliorhinus canicula) suggests that the mammalian pancreas may have a single, early origin in elasmobranchs.

Studies on the evolution of biological processes in vertebrates have historically been hindered by a lack of genetic information of different species. Previous studies often relied on morphological traits to attempt to reconstruct the evolutionary pathways of modern vertebrates. With the availability of more and more genetic data for a range of species, it has been possible to perform more accurate assessments of vertebrate evolution.

We already know that certain vertebrate biological processes - such as parts of our immune system - may have had their initial origins in cartilaginous fish (see The Shark Post - 29th Jan) so it is no surprise to learn that we may owe our pancreatic system to sharks too.

The researchers examined transcripts encoding genes involved in insulin regulation, glucose sensing, digestion, transcriptional regulation and other processes and compared them to transcripts in mammalian lineages. The researchers found that the mechanisms responsible for glucose sensing and insulin regulation are very similar across the vertebrate lineage. These features are therefore hypothesised to be commonly shared across all jawed vertebrates. Going one step further, the researchers propose that these shared mechanisms may have led to the development of the complex, glucose dependant brain of vertebrates.

Whilst the pancreas of elasmobranchs does differ to that of other fish and tetrapods in that the elasmobranch pancreas is a 3 peptide system and "higher" vertebrates have a 4 peptide system, the elasmobranch pancreas shares similarities to the mammalian pancreas as it is a distinct gland which has both endocrine and exocrine functions. These factors support the idea that the vertebrate pancreas evolved from a single, early origin and was possibly heavily blueprinted on the early shark pancreas.

Whilst this work has not yet been published, it may be viewed on bioRxiv here http://biorxiv.org/content/biorxiv/early/2014/06/06/006056.full.pdf

Mulley, J., Hargreaves, A., Hegarty, M., Heller, R. and Swain, M. (2014) Transcriptomic analysis of the lesser spotted catshark (Scyliorhinus canicula) pancreas, liver and brain reveals molecular level conservation of vertebrate pancreas function.

Shark Research - More evidence that magnets could be just the thing for repelling sharks!

Now why would anybody want to repel sharks? Well it turns out that sometimes not only can they be a nuisance - by getting themselves accidentally caught up in fishing gear - but some people get a bit nervous when there are sharks around and would prefer them to just darn well stay away when they are trying to go for a swim. People like Colin Barnet the Premier of WA - these people get so nervous about the idea of sharks being in the water when they are going for their morning swim that it makes them stay out of the water - oh no wait, sorry. Actually they still go into the water but they just want to try and kill all the sharks in the ocean so they feel safer when they go for their morning swim. It turns out we can't just dispatch of idiots like this, so some hard working scientists are looking at ways of creating repelling barriers which will be shark friendly (unlike drumlines and shark nets) and will minimise shark/human interaction.

Following on from a series of previous works (The Shark Post, 14th Feb, The Shark Post - 13th Jan, Craig P. O'Connell has been continuing investigations into the use of barium-ferrite permanent magnets for repelling sharks. Previous work showed strong evidence that fish with electrosensory capabilities - such as elasmobranchs - were usually successfully deterred by magnets. A key piece of research showed that bull sharks (Carcharhinus leucas) in particular could be repelled by magnets - a very interesting result as the lovely bull shark is one of the species which has got people such as Mr. Barnett so hot under the collar (you can read about my experiences of diving with these very awesome sharks here: The Shark Post, 11th Jan).

Like any good scientific ideas, the concept of using magnets as shark barriers requires a lot of investigation before it can become a reality. The latest research to come out of this project involved assessing whether or not other marine organisms might also be affected by the presence of magnets in the water (whilst it might be great having a magnet which repels sharks incorporated in your fishing gear, it's not so great if it turns out to repel all the other fish you are trying to catch too!)

C.P. O'Connell set up a series of experiments in the Bahamas to assess whether the reaction of teleost (bony fish) was significantly different to that of elasmobranchs (our cartilaginous friends). The research focused on ascertaining reactions of both types of fish to magnetic barriers and bait which was associated with a magnet. The results showed that teleost fish did not exhibit significant changes in their behaviour towards the magnets, whilst the majority of the shark species did. Not only did this study reaffirm the idea that magnets could be used to keep certain species of sharks away from fishing vessels and popular beaches, it also lent strength to the argument that behavioural impacts on other marine organisms would be minimal if magnets were deployed in the wild. Naturally there is still a long way to go before we have magnetic shark nets along our beaches, but so far the findings suggest that this could one day be a viable alternative to shark nets!

O'Connell, C.P. and He, P. (2014) A large scale field analysis examining the effect of magnetically-treated baits and barriers on teleost and elasmobranch behavior. Ocean & Coastal Management. 96: 130-137