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  

Shark Research - Mercury levels in shark fin soup

Researchers in the United States have examined bowls of shark fin soup from 50 US restaurants to assess the levels of monomethylmercury (MMHg) in each one.

MMHg is produced in aquatic food webs; owing to the fact that MMHg is not easily eliminated, it accumulates in organisms and species higher up the food chain will tend to exhibit higher levels of MMHg than those at the bottom. MMHg poses health risks to adults such as an increased chance of heart attack; it it also of particular concern in pregnant women as it can also transverse the placenta and has been linked to neurological development issues in the foetus.

Most fish and shark meat is known to contain high levels of MMHg. The US Environment Protection Agency recommends a daily consumption of no more than 7.4μg a day for a 74kg female. To give you some perspective, a 200g blue shark steak can contain between 36-390μg!

The researchers discovered that whilst average levels of MMHg found in shark fin soup were not incredibly high (they measured an average of 1.1μg MMHg in a 240ml bowl of soup), there was a large degree of fluctuation in the levels of MMHg, depending on which species the fin came from. Large, pelagic sharks which occupy higher trophic levels in the food chain have a greater dose of MMHg in their fins, whilst those lower down the food chain had less MMHg. The highest value recorded in a bowl of shark fin soup in this study was 8.2μg which exceeds the safe, recommended daily dose of MMHg.

This study highlights the fact that the consumer does not always know if the bowl of shark fin soup they are going to consume will pose a risk to their health, or will be within safe limits. If a consumer were to eat a bowl of shark fin soup as an appetiser and then follow it with a main course of fish it is highly likely that they would be ingesting a dose of MMHg far above the recommended daily level. Given the huge ecological impact shark fin soup has, this new data should be further reason to avoid this product!

The full article can be found here.

Shark Research - Insights into mortality of whale sharks in Atlantic and Indian Ocean tuna fisheries

A recent research article in Biological Conservation has examined mortality rates of whale sharks (Rhincodon typus) as a result of the European tuna purse seine fisheries in the Atlantic Ocean and Indian Ocean.

Tuna often associate with large marine species such as dolphins and whale sharks; tuna fishermen sometimes rely on sightings of these species to indicate the presence of large schools of tuna. Once tuna have been sighted, a net is set to encircle the shoal and the bottom of the net is drawn together, like a purse, to trap the fish. Owing to the fact that there are often large marine fauna close by, these animals can also become trapped along with the tuna.

This study used log book data and observer data to assess the number of whale sharks sighted, caught and killed in purse seine nets in the Atlantic Ocean and the Indian Ocean. The biggest incidence of whale shark mortality occurred in certain hotspots where whale sharks overlapped with the purse seine fishers. Overall the incidence of whale shark mortality in the Atlantic and Indian Oceans was relatively low - from 1995 to 2011, 2 whale sharks were reported to have died out of 186 encircled by the nets. In recent times, the purse seine fisheries have implemented new strategies for ensuring the survival of whale sharks caught in nets, such as the cutting of the net to allow the shark to escape.

This data is in stark contrast to whale shark mortality in the Pacific Ocean provided by the Western and Central Pacific Fisheries Commission (WCPFC). Between 2007-2009, 56 whale sharks died in purse seine nets - the most common reason cited was that the fishermen were not aware of the presence of the shark in the net before mortality occurred. As a result of this, the WCPFC has banned the setting of nets around whale sharks since the beginning of 2014.

Additionally, both the Indian Ocean Tuna Commission (IOTC) and the WCPFC have admitted that accurate data on the number of whale sharks encircled and killed by purse seine fisheries is difficult to obtain. The data for this study relied on the accurate reporting of whale shark mortality by purse seine skippers and observers - which only cover 10% of the European fleet.

More analysis of the tuna purse seine fishery and better observer coverage is needed in order to obtain a better picture of the mortality of large pelagics in the tuna purse seine industry.

Shark Research - Lateral line scales can make sharks fly

New research published in the Journal of Fish Biology has examined the scale pattern around the lateral line pores of the spiny dogfish shark (Squalus acanthias) and the shortfin mako shark (Isistius oxyrinchus).

The lateral line system is an important sensory organ in fish and is used to detect vibrations and movement in the surrounding water; this sense can be utilised in predator avoidance, schooling and prey detection. The lateral line runs down the side of a fish and comprises a series of sensory neuromasts, connected by tubules. Whilst some neuromasts remain below the dermis, at sections of the lateral line superficial neuromasts will be exposed to the outside environment via pores in the lateral line system.

Surrounding the pores of the lateral line system are the sharks' scales; unlike the scales of teleost fish sharks possess rough, placoid scales which (as well as being biologically similar to our teeth!) contribute to reducing drag whilst swimming and give sharks a rough, sandpaper like texture. The channelling of water over the neuromasts by the surrounding placoid scales will, of course, have an affect on the sensitivity of these sensory organs.

The fast swimming mako shark has a very different lifestyle to the spiny dogfish, which inhabits the ocean floor and has a much more sedentary lifestyle. The study found that the patterning of placoid scales around the neuromast pores in the mako shark may reduce turbulence in the water immediately surrounding the lateral line; this will affect lateral line sensitivity.

The arrangement of placoid scales around the neuromast pores in the spiny dogfish was entirely different, with S. acanthias exhibiting an entirely different divergent pattern to I. oxyrinchus. The placoid scales of I. oxyrinchus were orientated dorsally and ventrally from the pore, whilst those of S. acanthias were orientated exclusively ventrally away from the pore.

Whilst further research is required to fully analyse these differences across shark species, the results here suggest that the different lifestyles of these 2 shark species may be contributing to different sensory requirements in the lateral line and therefore different arrangement of the scales around the sensory organs.

Mckenzie, R. W., Motta, P. J. and Rohr, J. R. (2014), Comparative squamation of the lateral line canal pores in sharks. Journal of Fish Biology, 84: 1300–1311. doi: 10.1111/jfb.12353

Shark news - Megamouth shark caught off the coast of Japan

Following on from Tuesdays exciting news about the sighting of a goblin shark, a rare megamouth shark (Megachasma pelagios) has been caught off the coast of Japan. The specimen - which is only the 58th to have ever been found - was caught off the waters of Shizuoka last month and is currently on display at Marine Science Museum in Shizuoka.

Very little is known about these sharks but they are believed to be a filter feeding species which feeds primarily on krill. A single specimen was tagged and followed for 2 days and exhibited patterns of diel vertical migration (spending the daylight hours at depth and returning to shallower waters at night).

The megamouth shark is currently classified alongside white sharks (Carcharodon carcharias) and mako sharks (Isurus oxyrinchus) in the order Lamniformes (or mackerel sharks).

News source with pictures: http://www.wptv.com/news/local-news/water-cooler/rare-megamouth-shark-caught-in-waters-off-japan

Shark News - Drum lines removed from WA waters

At 2pm yesterday, the Western Australian Government removed the drumlines which had been set to catch target sharks off the coast of WA, Australia. Whilst this news will be warmly welcomed by the majority of the public - who overwhelmingly oppose the shark cull - there is a chance that the drumlines could be back in the water by the end of the year.

The initial policy to place drumlines in the water around Perth had always been a short term policy set to run for 13 and a half weeks the intended deadline for the removal of the drumlines set as 30th April. By negotiating the placement of the drumlines on a short term, "trial" basis, Colin Barnett was able to circumnavigate some of the laws which would otherwise prevent such a policy going ahead - such as the fact that the great white shark (Carcharodon carcharias) is a protect species in Australian waters.

Currently the Environmental Protection Agency (EPA) is assessing an application by the Barnett Government to extend the drumline policy for a further 3 years. The new submission to the EPA requests permission to put drumlines in the water for 4 and a half months of each year for 3 years and is requested to begin on November 15th 2014. Since the new proposal is for a much longer time period than the initial setting of the drum lines, the EPA has decreed that the policy must be subjected to the highest level of assessment.

Given a very strong public and scientific objection to the drumline policy, the hope is that the EPA will not allow the Barnett Government to continue with this policy long term.

You can read more about the assessment here 

Shark travel - whale sharks in the Philippines

For many people, the whale shark (Rhincodon typus) is top of their list to see. Whilst I have had the opportunity to encounter many types of shark on my global wanderings including white sharks, bull sharks, blacktips and grey nurse sharks, it feels as though I almost left the poor whale shark until last!

Capable of attaining lengths of up to 12m, the whale shark is the largest living fish in our oceans. However they are no threat to humans (unless you don't mind out for that powerful tail!) as their diet primarily consists of plankton which they filter out of the water.

Whale sharks are found all over the world in tropical and warm temperate seas, however there are some spots where sightings are quite common. I visited one of those such spots recently: Donsol in the Philippines.
Legazpi airport is the closest dropping off point for Donsol. I flew there from Manilla with Cebu Pacific Air (about 1 hour). Once you are at Legazpi airport a 1 hour drive through hilly, forested terrain will bring you to Donsol. I was pleasantly surprised at the lack of impact by tourism on Donsol - despite having a major tourist draw in the form of the whale shark, the town still feels very local and I didn't encounter too many other tourists there during my stay.

Donsol has plenty of local delicacies available at the market!

The peak time to see whale sharks here is over the Easter period, but the season runs from December to May. I had booked into a hotel in town - Giddy's Place (http://www.giddysplace.com/) and they were able to arrange my trip out with the whale sharks. Once you arrive at Donsol Bay you are assigned a Butanding Interaction Officer (BIO), a guide and a spotter and out you go on your boat for a maximum of 3 hours to try and find some sharks!

The spotters risk it all to get up high and spot whale sharks!

Known locally as butanding, the whale sharks are often found near the surface as they feed on plankton blooms. On our first day out we were incredibly unlucky - no sharks at all - only a pod of dolphins which put on a real show leaping clear out of the water! However on our return for day 2, we had a total of 5 whale sharks show up. The boat does not stop as it positions itself close to the shark - a quick leap from the moving boat and you are in the water with the largest fish in the world. And for anyone who might be worried that the clumsy monkeys in the water are capable of harassing these gentle giants, please rest assured that you will swim with everything you have just to try and keep up with the shark for 30 seconds. A few, slow flicks of their giant tail and the whale sharks had accelerated way past our group.

On one encounter, as the shark began to dive, I was lucky enough that it passed a few meters below me. I simply lay perfectly still in the water as the behemoth cruised past underneath me seemingly not bothered by my presence.  

Whale sharks are currently only legally protected in 10 countries - one of which is the Philippines. There is no doubt that the Philippine government has realised the tourist value of the whale sharks and this has led to them protecting the shark. I am happy to report that the standards of the guides and spotters on the whale shark trip were very high. All participants had to watch a video informing them of correct ethical conduct around the sharks - no touching, no riding, only 6 people maximum around a shark and only for a maximum time of 10 minutes. Once on board the boat and out at sea the crew enforced the rules and made sure that the sharks were not harassed. With such pressure on sharks from the trade for fins (a whale shark fin can fetch up to USD$10,000), tourism is the best chance we have now to encourage governments to really make the effort to protect their sharks from poaching.

To see a video of my time in Donsol, click the link below!

Shark research - evolution of the vertebrate jaw

A recent article published in Nature has found new evidence that the origins of the vertebrate jaw may lie with bony fish, as oppose to cartilaginous fish as previously thought.

By examining a 325 million year old, Palaeozoic shark-like fossil (Ozarcus mapesae), the researchers found many similarities to the visceral branchial arch arrangement of osteichthyans (bony fish). This has thrown into question the existing idea that cartilaginous fish are responsible for the origin of the vertebrate jaw.

All vertebrate embryos develop pharyngeal arches - in fish these develop into the gill (or branchial) arches and in humans they ultimately become part of the larynx and trachea.

Cartilaginous fish (sharks, skates, rays and chimeras) are often described as "primitive fish", and are thought not to have changed much since their original evolution. Bony fish (or Osteichthyes) are considered to be the derived state and to have a more "modern" physiology. However, this new shark-like skeleton suggests that far from being unchanged since their evolutionary origin - around 420 million years ago - sharks may have undergone several evolutionary adaptations along the way and that our own mammalian jaw may have a closer evolutionary history with that of bony fish rather than cartilaginous fish.

Pradel, A., Maisey, J. G., Tafforeau, P., Mapes, R. H. and Mallatt, J. (2014) A Palaeozoic shark with osteichthyan-like branchial arches. Nature (16th April 2014)

Shark facts - Wobbegongs!

There was previously thought to be just over 350 species of sharks, but genetic analysis has now put that number at over 400! Of course, when many people think of a shark, they perhaps imagine big, pelagic sharks such as the great white (Carcharodon carcharias). However sharks come in a wide range of shapes and sizes from the eel-like frilled shark (Chlamydoselachus anguineus) to the gentle, filter feeding basking shark (Cetorhinus maximus). One of the aims of this blog is to pass on a bit of information about some of these weird and wonderful sharks. 

Perhaps one of the hardest group of sharks to spot in the wild are the wobbegongs. Wobbegongs - or carpet sharks - belong to the family Orectolobidae. 

Wobbegongs can be very tricky to spot as they are very well camouflaged against the sea floor!

Wobbegongs are bottom dwelling sharks and spend a lot of time motionless on the sea floor. They are found in the Western Pacific - mostly in the waters around SE Asia and Australia and occupy tropical to temperate waters. They are primarily ambush predators and feed on bottom dwelling invertebrates such as cephalopods, crabs, lobsters and even bony fish.

Whilst they don't feed on humans and are generally quite placid animals, wobbegongs have been known to bite when provoked. Owing to the fact that they can occupy quite shallow water they can get stepped on quite easily and have been known to inflict minor injuries as a response. Divers are usually able to get very close to wobbegongs owing to the relaxed nature of the shark.

Of the 12 recognised species, 3 of them have been classified as Near Threatened in the IUCN Red List - the spotted wobbegong, ornate wobbegong and banded wobbegong. The remaining species are classified as Data Deficient. 

A close up of a wobbegong near Stradbroke Island, Brisbane

Wobbegongs can be found in many places around the Australian Coast. The little fella above was snapped on a trip I took with Manta Lodge and Scuba Centre from Stradbroke Island, Queensland.

Shark research - Port Jackson sharks show learning and memory capabilities

New research has found that Port Jackson sharks (Heterodontus portusjacksoni) are capable of conditioned learning and some memory retention.

The researchers exposed Port Jackson Sharks to two different stimuli - air bubbles and an underwater LED. Each stimulus was activated prior to the release of a food reward and the response of the shark post-stimulus was recorded.

Sharks which were exposed to the air-bubble stimulus showed a reduction in the time taken to react to the stimulus, in anticipation of a food reward. Response behaviours included biting or vigorous respiratory pumping such as would be observed when searching for buried prey in the wild.

The group which was exposed to the LED stimulus showed no modified behaviour towards the stimulus suggesting no anticipation of reward. This could be owing to the fact that, as nocturnal predators, Port Jackson sharks do not rely on vision for prey detection and capture and therefore the LED stimulus was unable to elicit a response.  

Owing to the fact that there was a period of 24 hours between trials, the Port Jackson sharks were able to retain memories of the association between the stimulus and reward for at least 24 hours and one of the sharks even remembered the association for 40 days.  

Port Jackson sharks are an excellent model species for this study as they are reef associated and have been shown to return to the same point on the reef up to 24 hours later after being displaced. This suggests that they must have some capacity for spatial memory.

This study demonstrates, for the first time, the learning capabilities of a benthic elasmobranch. Of all shark species, benthic sharks are the group with the smallest brains; previous studies on teleost fish have demonstrated a link between brain size and cognitive ability and therefore the researchers surmise that our understanding of cognitive ability in sharks in greatly lacking.  

Guttridge, T. and Brown, C. (2014) Learning and memory in the Port Jackson shark, Heterodontus
portusjacksoni. Animal Cognition (17): 415-425

Shark News - The WA Shark Cull Update

Since The WA Government announced their plans to set drum lines to catch sharks, the shark cull has been strongly opposed by members of the public, the scientific community and even some celebrities. The Department of Fisheries, WA seems to have conflicting views on the policy. On the one hand they promote the cull on their webpage, on the other they state quite clearly:

"Despite their sometimes-menacing appearance and 'man-eating' reputation, sharks seldom cause harm when interacting with humans. The presence of some shark species as ‘apex predators' – occupying the very top level of the food web – is actually an indication of a healthy marine environment."

For a while, the hopes of all opposed to the WA shark cull hinged on the indication that the Environmental Protection Authoriy (EPA) of WA would assess the shark cull and potentially overturn the policy. However, on the 12th March the EPA announced that they would not assess the shark cull as they believed the cull was not likely to significantly impact the environment.   

Since the cull began over 100 sharks have been caught. The policy of the government is to release any shark smaller than 3m and to destroy any shark which is one of the 3 target species and over 3m long; so far over 30 sharks being destroyed and 14 found dead on the line. The species which has been caught with an overwhelming frequency is the tiger shark (Galeocerdo cuvier).  

A female tiger shark which was destroyed as part of the policy. Photo credit: Bruce the Rib, Sea Shepherd  (c) Jodi Hayes 

In a recent press release, fisheries minister Ken Baston stated: "“We have caught and destroyed a number of large sharks within one kilometre of selected beaches, at a time of year when our beaches are crowded. This catch data proves there are a large number of big sharks near these beaches". He also commended the program, saying that the methods were "working well". 

This cull has brought to light the fact that large, tiger sharks frequent the inshore waters around WA and some of the most popular beaches...yet according to the Australian Shark Attack File there was only a single fatality from shark attacks in WA in 2013, and 2 in the previous year. Whilst any loss of life is an incredibly tragic event, it is hard to imagine that these low numbers really warrant such an expensive, controversial and damaging policy as the one Colin Barnett has implemented in WA with his shark cull.  

However, there could be hope for the future. There is a limit on how long the drum lines may remain in the water and the EPA has stated they expected that "a continuation of the proposal beyond April 30 2014 would be referred for consideration". 

Shark research: Spiny dogfish like their salt!

New research published in Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology has found that the North Pacific spiny dogfish (Squalus suckleyi) have difficulty adjusting to low salinity levels in the water.

The North Pacific spiny dogfish is known to tolerate a narrow range of salinities; whilst this species has been found in salinities of less than 25‰ in the wild, this low salinity cannot be tolerated for long. This is in contrast to certain other elasmobranch species such as the blue shark (Prionace glauca) which has been known to infiltrate river systems for extended periods of time.

Elasmobranch species moving between salt water and fresh water can experience changes in the concentration of Na^+, Cl^- and urea in their plasma, the pH of their blood and the volume of body water as they attempt to readjust to their new environment.

In this study, the researchers exposed S. suckleyi to dilute saltwater at a salinity of 21‰, in order to assess the time taken to acclimatise and the physiological effects this hyposmotic solution had.

They found that the concentration of plasma Na⁺, Cl^- and urea dropped, and the body weight of the experimental animals increased - most likely owing to an influx of water. Whilst S. suckleyi was able to begin to balance the Na⁺ and Cl^- concentrations, possibly by active transport, steady states in the concentration of plasma urea was not achieved and it is hypothesised that this is the key limiting factor for the survival of the North Pacific spiny dogfish in low saline environments.

Whilst it appears as though this species can tolerate an environment of 21‰ for a short period of time, the ability to regulate key body processed in a lowered salt environment would appear to restrict the long term survival of this species in water of this salinity.

Samuel C. Guffey, Greg G. Goss, Time course of the acute response of the North Pacific spiny dogfish shark (Squalus suckleyi) to low salinity. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology. Volume 171, May 2014, Pages 9-15.

Shark research - Egg Capsule Evolution

An international team of researchers have constructed a phylogeny of chondrichthyan egg capsules by examining their morphological traits.

Chondrichthyan fish have cartilaginous skeletons - in contrast to osteichthyan (bony) fish - and comprise the Elasmobranchii (sharks, skates and rays) and the Holocephali (chimaeras). Whilst vivparity (giving birth to live young) dominates as the reproductive strategy in modern day Elasmobranchs, the Holocephali are exclusively oviparous (egg layers). The authors suggest that oviparity is the likely ancestral state for cartilaginous fish, whilst viviparity is assumed to have evolved several times in the Chondrichthyan lineage.

Chondrichthyan egg capsules are currently categorised into 10 morphotypes, with 8 of these types known from the fossil record. Using cladistical analysis of morphological traits of the egg capsules, the researchers attempted to see if the relationship would yield a phylogenetic signal.

They found that a very strong Elasmobranch group was generated, with very clear morphological similarities in the egg cases of Heterodontus, Orectolobus, Scyliorhinid and Rajoidae. The Holocephalan egg cases showed a greater similarity to the egg cases of extinct species than modern day Elasmobranchs.

The results suggest that the Elasmobranch egg capsule is the derived state and the ancestral reproductive state in both live bearing and egg laying jawed vertebrates is internal fertilization paired with clasper organs.

Jan Fischer, Martin Licht, Jürgen Kriwet, Jörg W. Schneider, Michael Buchwitz & Peter Bartsch (2014) Egg capsule morphology provides new information about the interrelationships of chondrichthyan fishes, Journal of Systematic Palaeontology, 12:3, 389-399,

Shark news - the truth about shark nets

The recent controversy regarding the shark cull in Western Australia has got a lot of people talking about the ways in which governments choose to protect their beaches from sharks - usually in the form of drumlines and shark nets. Several people I know have expressed surprise about the fact that shark nets are intended to kill sharks - there seems to be a public perception that netting a beach is a benign practice which simply keeps sharks away from the shore. In fact, shark nets are designed to kill large fish and mammals which become entangled and eventually drown.

Owing to the fact that shark nets are a non-discriminatory fishing process, it is not only sharks which are caught up; the nets trap many other species which swim too close and become entangled - this is known as bycatch. Dolphins, dugongs, turtles and whales are some of the species known to be caught up in shark nets (1, 2).

There is a great deal of controversy of whether or not netting a beach has any effect on reducing shark attack numbers. The construction of the nets does allow animals to swim below and around and some shark net programs have found a large degree of the entangled sharks to actually be on the beach side of the net! (3)

In Australia, shark nets have been in place along the Queensland coast as part of the Government's Shark Control Program (SCP) since 1962. In the last 10 years 6,252 sharks have been caught as a part of this program, over a third of which were tiger sharks (Galeocerdo cuvier) (4). The remaining numbers are made up of another 36 species of shark, 22 of which are grey nurse sharks (Carcharias taurus). Also known as the ragged tooth shark, C. taurus is a common aquarium shark and a popular shark to dive with owing to its placid nature.

Of more concern are the number of endangered species which are killed by shark nets - the SCP reported catching many species listed as Vulnerable in the IUCN Red List such as the grey nurse shark, the shortfin mako (Isurus oxyrinchus) and the whale shark (Rhincodon typus) (5). Most shark species exhibit slow growth rates and tend to take a long time to reach maturity, which means that once their numbers are depleted it is difficult for them to rebuild the population.  

The New South Wales (NSW) Shark Meshing Program (SMP) reported "72 interactions" with non-target species, vs. only "32 interactions" with target species. The non-target species included entanglement by Port Jackson Sharks (Heterodontus portusjacksoni), Southern Eagle Rays (Myliobatis australis) and 2 species of turtle (6). Two humpback whales were also entanglesd and whilst they swam away, they remained entangled as they swam and thus their survival is by no means assured.

Like all shark net projects, the NSW SMP is under scrutiny to perform in an ecological manner and to reduce bycatch numbers, and they do implement certain methods to attempt to reduce interactions with non-target species - for example the shark nets are removed for the whale migratory seasons from May to August. However, the fact remains that shark net programs are responsible for the death of a great many species of sharks, marine mammals and reptiles and are acting in response to a threat which is more perceived than real. In 2013, 10 people died globally from shark attacks (7) vs. an estimated 388,000 deaths from drowning worldwide annually and - the biggie - approximately 1.24 million annual deaths from road traffic accidents (8). It just seems as though the money and time of any government could be better invested in tackling the real dangers which exist in society, instead of using methods which are incredibly destructive to the marine environment in order to simply make people feel better about going in the water.

1. Qld's Fisheries Department defends shark nets amid trapped whale worries
2. Dolphin deaths a tragic find for local kayakers
3. Fisheries Scientific Committee
4. Department of Agriculture, Fisheries & Forestry - Shark Catch Numbers
5. IUCN Red List
6. Shark Meshing (Bather Protection) Program 2012-13 Annual Performance Report
7. International Shark Attack File (ISAF)
8. World Health Organisation - Factsheet - Drowning

Shark Research - Researchers in Brazil find new techniques to improve the survival rate of tiger sharks caught in longline fisheries

Researchers in Brazil have used tagging methods to study the mortality and behaviour of juvenile tiger sharks (Galeocerdo cuvier) after they had been caught and released from bottom longline fishing gear.

The researchers tagged 21 tiger sharks caught in longlines during the course of the experiment. The sharks were hooked by the jaw using circle hooks as oppose to J-hooks - a method which has been previously proven to improve survival rates post-release. After the sharks were released, their movements were monitored via satellite. Most of the sharks caught were released in good health and none of the individuals died within 30 days of release, indicating that this species could be robust enough to successfully survive catch and release from longline circle hooks when caught as bycatch. This could be particularly important in this region of Brazil owing to the fact that all the sharks caught in this study were juveniles and therefore had no opportunity to reproduce. The authors also noted that the fishing pressure on the local shark population in this region was particularly high as artisanal fishermen in neighbouring waters fishing with gillnets and reported a much higher mortality rate for tiger sharks than reported from this study using longline circle hooks.

Interestingly, the researchers also discovered that tiger sharks released after capture tended to move into deeper water and did not return to the same area where they were captured for a considerable time. This suggests that these catch and release methods could be employed to successfully relocate problem tiger sharks in the area - a strategy which would be preferable to culling.

Other studies have predicted that tiger sharks are a keystone species in many ecosystems, and the removal of this apex predator would cause a great deal of disturbance in the ecosystems they are associated with. Therefore effective management strategies to minimise the impact of the fishing industry on tiger sharks are essential.  

Sharks, along with other marine animals, are often caught unintentionally by the fishing industry as bycatch and estimates suggest that the bulk of this is ascribed to longline fisheries. The fact that tiger sharks could survive catch and release - at least if circle hooks are used for the capture - could be used to facilitate the effective management of longline fisheries with regards to shark conservation.

André S. Afonso, Fábio H.V. Hazin, Post-release survival and behavior and exposure to fisheries in juvenile tiger sharks, Galeocerdo cuvier, from the South Atlantic, Journal of Experimental Marine Biology and Ecology, Volume 454, May 2014, Pages 55-62
Link to the paper

Other posts related to this one:

Brazil looks at better ways of keeping beaches safe

Shark Research: Public perceptions of shark conservation

New research has conducted a survey on aquarium goers to assess the views of the public on sharks and their conservation.

The survey, published in the journal Marine Policy, posed a series of questions related to shark conservation to the visitors of the National Marine Aquarium in Plymouth. The questions focused on assessing the respondents general knowledge of sharks as well as their knowledge of shark fisheries. Whilst nearly all survey participants displayed a good general knowledge of sharks, there was a large degree of uncertainty when questioned about shark fisheries with 21% of respondents incorrectly believing that sharks were not fished in European waters and 19% answering (incorrectly) that shark meat was not consumed in the UK.

The participants were also interviewed regarding their perception of sharks. Approximately two thirds of the survey group had a positive image of sharks and individuals who had encountered sharks in the wild displayed a more positive attitude towards sharks.

Public perception of sharks could be an important factor influencing shark conservation. When people hold high views of wild animals, they have a tendency to participate in activities to promote the protection of those animals and to avoid products and practices which could be detrimental to the survival of that species in the wild. Public opinion can be a strong driving force for policy making and bolstering protection for certain animals; a well informed and motivated public may hold the ability to drive change in terms of shark conservation.

Sharks are under threat globally owing to the pressure exerted on many species from shark finning and fishing bycatch and the study states that around half of sharks in European waters are at risk of becoming endangered or threatened with extinction. Low fecundity, slow growth rates and length of time taken to reach maturity mean that most shark species do not rebound easily once their numbers have been depleted. Finding more ways to drive public perception of sharks and to motivate individuals to become involved with shark conservation could be a real driving force for preventing the decline of these vulnerable species.  

Shark Research: Population composition of blue sharks in the Central Atlantic

A group of researchers has examined population structure, size, abundance and migration patterns of blue sharks (Prinace glauca) in the Azores Archipelago in the Central North Atlantic.

Unlike many other shark species, blue sharks are relatively productive and may attain high abundances locally. This is reflected in the fisheries catch composition which the researchers monitored in the local area where blue sharks constituted 81.5% of the total catch in terms of number of individuals caught.  

Blue shark composition varies with sea surface temperature (SST), time of year and lunar cycle. The highest catch rate of blue sharks in the Central North Atlantic occurred during the winter months whilst the summer months yielded the lowest catch rate. This is congruent with evidence that female blue sharks migrate in the warmer months and appear off the coasts of Ireland and SW England. The highest catch abundance of blue sharks also coincided with the coolest SSTs, with the highest catch rate occurring in waters of 17.5°C and the lowest at the higher SST of 23°C. Evidence of several life stages of the blue shark in the Central North Atlantic indicates that this is an important ecological area for blue shark populations from both sides of the North Atlantic, as well as being a nursery area for blue sharks.

Owing to the over exploitation of many shark species by the fisheries industry, in depth knowledge of population structure and composition of shark species is an important tool in assessing vulnerability of each species. The blue shark is the most frequently caught pelagic shark species by the fisheries industry, with an estimated 86,000 tonnes fished per year; in recent years the swordfish fisheries have begun to target blue sharks owing to a reduction in the swordfish catch in the region.

Vandeperre, F., Aires-da-Silva, A., Santos, M., Ferreira, R., Bolten, A. B., Serrao Santos, R. and Afonso, P. (2014) Demography and ecology of blue shark (Prionace glauca) in the central North Atlantic. Fisheries Research. 153, 89-102

Shark research - insights into trophic position of sharks

Scientists at Shanghai Ocean University have used stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) to assess trophic postions of 5 shark species.

Previous work on the trophic levels of sharks has primarily used stomach content analysis to assess where sharks sit in the food web. Assessing trophic position by examining stable isotope ratios is a less invasive method than stomach content analysis.

Sharks are apex predators and play a pivotel role in marine ecosystems. Detailed understand of where apex predators sit in the food web, in relation to each other, gives us a better understanding of the top down effect they may have on an ecosystem.

The five species included in this study were the blue shark (Prionace glauca), bigeye thresher (Alopias superciliosus), silky shark (Carcharhinus falciformis), scalloped hammerhead (Sphyrna lewini) and oceanic whitetip (Carcharhinus longimanus). These five species are all caught by the Chinese longline fleet in the mid-east Pacific.

Stable isotope analysis (SIA) can be used to assess a number of mechanisms in the food chain. By examining δ¹⁵N isotopes in organisms, researchers can make an estimate of the position that organisms inhabits in the food web. δ¹⁵N isotopes move through the food chain as organisms consume each other. Therefore organisms residing in a higher position in the food web will have higher δ¹⁵N values than those further down.

The researchers also examined δ¹³C isotopes; these isotopes originate from the primary producer and remain relatively unchanged as they make their way through the food web; they can be used to give an indication of the source of primary production supporting the entire food web.

From these analyses, the team discovered that A. superciliosus occupies the highest trophic position in the food web; possibly owing to the fact that this species consumes more cephalopods than the others - cephalopods have higher δ¹⁵N and δ¹³C values than fish prey. The team also discovered that A. superciliosus had the largest variation of δ¹⁵N - possibly owing to its highly migratory lifestyle.

C. longimanus occupied the lowest trophic position in the food web.

Li, Yunkai , Gong, Yi , Chen, Xinjun , Dai, Xiaojie and Zhu, Jiangfeng. Trophic ecology of sharks in the mid-east Pacific ocean inferred from stable isotopes. Journal of Ocean University of China 13(2):278-282

Shark research - Sharks get their speed from spring loaded spines

New research has discovered that the vertebral columns of sharks behaves like a spring, providing power when swimming.

Sharks differ from most other fish in that their skeleton is made of cartilage instead of bone. By examining whole body curvature of the spiny dogfish (Squalus acanthias), and strain placed on the vertebrae of sharks during swimming, a team of researchers have discovered that the entire vertebral column bends during locomotion. This indicates that the spine is behaving like a spring and providing power to the sharks when swimming.

The morphology of the spine of cartilaginous fish appears to allow for spring loading. The vertebral column of S. acanthias displayed an open, intracentral canal, covered by a velum layer which effectively strengthens the vertebral column and could facilitate elastic recoil of the entire spine. This recoil in the cartilaginous vertebral column of sharks assists undulatory swimming by providing springback power to the motion of the tail. A shark requires 6% of its metabolic power to flex the tail and load the spring, but this investment is a relatively inexpensive cost for the recoil power generated.  

The results indicate that the bodies of sharks have been positively selected for speed, which is in keeping with the lifestyle of many large, metabolic sharks.

This method of swimming differs from bony fishes, whose spines consist of hardened vertebrae and flexible joints, and may provide a clue for one reason why sharks diverged from the ancestral state of having a bony skeleton.

M.E. Porter, Candido Diaz Jr., Joshua J. Sturm, Sindre Grotmol, A.P. Summers, John H. Long Jr., Built for speed: strain in the cartilaginous vertebral columns of sharks, Zoology, Volume 117, Issue 1, February 2014, Pages 19-27, ISSN 0944-2006, http://dx.doi.org/10.1016/j.zool.2013.10.007

Shark research - Sharks vs magnets 2: visually deprived lemon sharks show heightened awareness of electric stimuli

Following on from their previous research (see The Shark Post 13th Jan), researchers at University of Massachusetts have investigated the reactions of visually impaired lemon sharks to magnets.

The team had already ascertained that C8 barium-ferrite (BaFe12O19) permanent magnets successfully repelled bull sharks, but were unsure as to the success magnets would have on repelling sharks which are more reliant on their visual system. The aims of this study were to ascertain whether magnets would successfully repel visually impaired juvenile lemon sharks (Negaprion brevirostris).

The researchers hypothesised that restricting the vision of lemon sharks would lead to a greater reliance on short range senses such as electro reception - an effect known as context dependent switching. In the wild the visual field of a marine animal could be restricted by bad visibility caused by environmental conditions such as turbidity. In this instance,

The sharks were visually impaired using a short term, simple surgery technique to suture closed the nictitating membrane of the eye. Once the experimental phase was completed, the sutures were removed, restoring the vision of the sharks. All sharks showed successful recovery post-experimentation.

The experimental area was separated into different compartments, both with and without magnets present. The sharks were divided into groups with differing levels of visual impairment. By assessing the behaviour of the different shark types to the magnets, the researchers were able to assess what impact visual impairment had on context dependent switching of senses.

Visually impaired sharks did indeed enter areas with magnets less frequently than sharks with visual ability. These results suggest that magnetic repellents would be more successful when sharks are visually impaired, and this could translate to the visual impairment experienced in turbid waters. Magnets could be an appropriate method of deterring all species of sharks from entering turbid regions, and not just those which are less reliant on their visual system to begin with.  

Connell, C., Guttridge, T., Gruber, S., Brooks, J., Finger, J. and He, P. (2014) Behavioral modification of visually deprived lemon sharks (Negaprion brevirostris) towards magnetic fields. Journal of Experimental Marine Biology and Ecology 453:131-137

Shark Research - new low cost survey techniques could aid shark conservation

Recent research conducted by researchers at l'Acquario e Civica Stazione Idrobiologica di Milano in Italy has led to the development of a low cost method to assess shark assemblages in remote areas.

The research was conducted at 2 reef locations off the coast of Sudan. Shark populations are of concern in this region as there have been reports of illegal fishing of sharks around the Sudanese coast. The authors also comment on a lack of control over Sudanese shark fisheries.

The researchers used stationary underwater cameras to video shark activity during the day, and laser pointers to infer the total length of the sharks filmed. By gathering data in this manner, the team were able to compile information regarding species, total length, sex, ecology and behaviour of pelagic and reef associated sharks in this region. In total 6 species were recorded from the reefs: common thresher shark (Alopias vulpinus), scalloped hammerhead (Sphyrna lewini), whitetip reef shark (Triaenodon obesus), grey reef shark (Carcharhinus amblyrhynchos) and tiger shark (Galeocerdo cuvier).  

The equipment and methods used in this study are relatively inexpensive and non invasive to the marine life. The survey techniques were also suitable for the adverse conditions of the study sites - both sites exhibited strong currents and relatively deep thermoclines which some of the shark species remained beneath. The relative ease with which these methods can be employed could facilitate the monitoring of shark assemblages in remote areas and contribute to data gathering of shark assemblages which presently, may be quite data deficient. This, in turn, could lead to a greater enforcement of shark regulation in these areas.

Danilo Rezzolla, Ginevra Boldrocchi and Tiziano Storai. Evaluation of a low-cost, non-invasive survey technique to assess the relative abundance, diversity and behaviour of sharks on Sudanese reefs (Southern Red Sea) . Journal of the Marine Biological Association of the United Kingdom, available on CJO2014. doi:10.1017/S0025315413001781.    

Shark research - Global warming could threaten whale shark populations

A research article published in Global Change Biology coupled existing whale shark distribution to global climate forecasts to predict how climate change may affect whale shark (Rhincodon typus) populations.

The research, led by Ana Sequeira at The University of Adelaide, found that rising sea temperatures may reduce the available habitat of whale sharks, and are likely to shift current whale shark populations towards the poles.

The researchers used sightings of whale sharks, recorded by tuna purse-seine fisheries, to assume the current global distribution. The data had been collected over different seasons and in some cases recorded whale shark sightings from over 30 years ago.

Currently, the range of the whale shark is commonly between 30-35°N. By combining this data with climate forecasts derived from global circulation models - which predict that existing sea surface temperatures will increase by at least 2°C on average by 2070 - the researchers discovered that the suitable range of the whale shark will be pushed towards the poles by 2070.  

Perhaps more worryingly, the team predicted that the available suitable whale shark habitat will contract with rising sea temperatures. Ectothermic organisms, such as whale sharks, are sensitive to temperature change and rises in sea temperature lead to an increase in metabolic activity which raises food intake requirements. Other threats to whale sharks include illegal fishing, shipping activity and habitat disturbance.

The whale shark is listed as Vulnerable in the IUCN Red List (http://www.iucnredlist.org/details/19488/0) and the results of this research suggest that current management policies of whale sharks should be revised to attempt to guarantee the global survival of whale sharks.

Sequeira, A. M. M., Mellin, C., Fordham, D. A., Meekan, M. G. and Bradshaw, C. J. A. (2014), Predicting current and future global distributions of whale sharks. Global Change Biology, 20: 778–789. doi: 10.1111/gcb.12343

Shark research - Post release mortality rate of shark bycatch higher than first thought

A study conducted primarily by the University of Miami has examined post release mortality in 5 shark species.

Bycatch - where a non-target species is caught by non-discriminatory fishing methods - is a common problem of the fishing industry. Owing to the fact that many species of shark are endangered and for the sake of upkeeping good fishing practice, bycatch is often required to be released alive. Whilst there have been studies on the successful handling and release of shark bycatch, there have been few studies on the post release mortality of sharks.

In their research the team, led by A. J. Gallagher, looked at whole blood lactate, pH values, pCO2 and shark size to assess the physiological disturbance that hooking has on a shark and to ascertain if any of these disturbances linked to post-release mortality. Smart Position or Temperature Transmitting (SPOT) tags were deployed on 3 of the species (bull, tiger and great hammerhead sharks) to assess potential post-release survival.

The researchers included 5 shark species in the study: blacktip shark Carcharhinus limbatus, bull shark Carcharhinus leucas, great hammerhead shark Sphyrna mokarran, lemon shark Negaprion brevirostris and tiger shark Galeocerdo cuvier. The species were caught on baited drumlines using circle hooks - which have been shown to lower mortality rates in sharks. The hooks afforded the sharks a 23m radius to swim around once caught. The hooks were checked periodically and caught sharks were brought alongside the boat in order to take samples and to measure the total length.

The results showed that of the 5 species, tiger sharks were the most likely to survive post release capture with 96.4% of the individuals caught transmitting tag data 4 weeks after the study. Blacktip sharks appeared to be the most vulnerable to hooking, with their physiological disturbances ranking the highest of the 5 species studied. The team also found that of all the measurements, blood lactate levels seemed to correlate closest with post release survival. Species which may need to use short bursts of energy to evade predation from larger sharks - such as the blacktips - displayed high levels of lactate in their blood. Lactate is generated when periods of sustained exercise cause animals to undergo a shift from aerobic to anaerobic respiration. Tiger sharks - which most likely rely on stamina and sustained swimming as oppose to bursts of energy - exhibited very little change in their lactate levels.

These stress responses - such as changes in lactate and pH - can affect the short term and long-term survival of an animal. This study found that some sharks - such as tiger and lemon sharks - are able to recover very quickly from the stress of being hooked. However, other species - such as blacktips and great hammerhead sharks - suffer greatly from post capture stresses as displayed by large changes in their blood lactate levels. This is translated to higher supposed mortality rates post capture - only 53.6% of great hammerhead sharks transmitted tag data after 4 weeks compared to 96.4% of tiger sharks.

The finding here are important as the fishing industry may currently be assuming that if a caught shark swims away from the boat that it will survive. However, the results here show that there are huge variations in the ability of different shark species to recover from the stress of being hooked and the post release survival rate is actually quite low in some species. Owing to the fact that sharks are threatened globally and live release of bycatch is currently an accepted strategy for dealing with unintentionally caught sharks, more data on actual post release survival levels will help determine whether or not hooking certain species of sharks will impact upon the long term survival of the species.

Gallagher, A.J., Serafy, J.E., Cooke, S.J. and Hammerschlag, N. (2014) Physiological stress response, reflex impairment, and survival of five sympatric shark species following experimental capture and release. Marine ecology progress series. 496: 207-218 




 

Shark news - Thousands turn out to protest the WA shark cull

Thousands of people across Australia turned out today to protest the decision of the West Australian government to cull sharks in the seas surrounding Perth. Protest rallies around Australia were scheduled to happen at staggered times across the country so that each state would be protesting at the same time.

Despite the heat of the day, protesters in Melbourne braved the sun to gather on the steps of the State Library of Victoria. Nationwide, an estimated 6,000 protesters gathered at Cottesloe Beach in WA (1) Manly Beach in NSW (2), Glenelg in South Australia (3) and other locations across the country.

In Melbourne protesters gathered at the State Library of Victoria

When Colin Barnett, the premier of WA, launched his policy to catch and kill large sharks he most likely did not expect the enormous national and international backlash his policy would cause. Armed with banners and decked out in all manner of shark related attire, protesters sent a clear message to the Barnett government - stop killing our sharks!

Protesters proudly displayed
homemade banners

Guest speakers at the rally included shark conservation groups such as Fin Free Melbourne, zoology and genetics major Safia Maher, fisherman Rob Embury, and Shark Defence Australia President Jordan Crooka. The message was clear - the cull has no support from the scientific community or the army of surfers, scuba divers and water users who had turned out to protest Barnett's policy.

Fisherman Rob Embury spoke up against the cull

The rally finished with a march from the State Library to Flinders Street Station. It was heartening to see the crowds marching down Swanson Street cheering "Save our Sharks" and "We don't want your bloody bait!" as a message to the Barnett government to find another way to protect beaches. It was a true tour de force of Australians standing up for their wildlife. Onlookers in the city had their smartphones out and were taking pictures of the protest as it made its way to Flinders Street.

That's the way to dress for a ride!

With so many people gathered nationally to protest this policy it feels as though Colin Barnett is the last man standing who supports the cull. It is hard to imagine that he can continue to stand by and keep his hooks in the water when their is such immense pressure from his countrymen to stop the slaughter.

1) http://au.news.yahoo.com/a/21207700/wa-shark-cull-thousands-gather-at-cottesloe-beach-as-catch-and-kill-protests-ramp-up/
2) http://www.smh.com.au/environment/conservation/thousands-protest-wa-shark-cull-at-manly-beach-20140201-31tiy.html
3) http://www.adelaidenow.com.au/news/south-australia/at-glenelg-and-beachside-suburbs-around-australia-thousands-of-people-protest-controversial-western-australia-shark-cull/story-fni6uo1m-1226815605616

Shark News - Weekend rallies set to oppose WA shark cull

Things are certainly hotting up in Australia as people from around the country will be gathering at one of 16 events occurring nationwide this Saturday to protest the shark cull due to happen in WA. There will also be an international additional event happening in New Zealand. The events have been scheduled in every state and will be happening at a specific time in each state so that the nationwide protests all begin together.

This will be the second wave of rallies across Australia to protest the shark cull. The first nationwide protests happened on the 4th January and made the national news. Since then the movement against the cull has gained  momentum with more Australians lending their support to protecting their wildlife. The cause has also received international attention with celebrities such as Ricky Gervais coming on board to send a message to the government of WA. A recent poll run by UMR showed that 80% of Australians oppose the cull.

The decision by the WA government to implement lethal shark preventative measures came after an increase in shark attacks in the state in recent years with 7 fatal shark attacks between 2011 and 2013. The premier of Western Australia - Colin Barnett - announced the decision to set baited drum lines late last year. Since then the proposal has been fiercely protested by the general public. The cull has also been opposed by leading shark scientists as there is very little evidence to indicate that shark culling is an effective measure to increase public safety. Many parties opposed to the cull also argue that the number of people killed by sharks per year pales in comparison to people killed in rip tides, drownings or road traffic accidents. Despite the overwhelming lack of scientific or public support, Mr Barnett is still standing by his decision to continue with the cull until at least the end of April 2014.  

The first shark to fall victim to the baited drum lines was in the south-west of the state last weekend. Whilst the catching and shooting of the animal - a tiger shark (Galeocerdo cuvier) - caused public outrage there was an even more emotive point to the kill. According to news sources, the commercial fisherman hired to carry out the cull had misidentified the shark as a bull shark (Carcharhinus leucas). Given the striking difference between the two species this mistake is inexcusable and throws into question whether the individual should even be carrying out the job.

Tiger sharks and bull sharks are listed as "Near Threatened" in the IUCN Red List whilst white sharks (Carcharodon carcharias) are listed as "Vulnerable". Colin Barnett has appealed to federal law to lift the protection on these sharks so that he may carry out his cull.

Despite Mr Barnetts seemingly immovable stance on the subject, the protest rallies this weekend look set to be well attended and hopefully will send a message which the government will find difficult to ignore.

Shark research - Evidence that human immunoglobin originated in sharks

Researchers at China Agricultural University in Beijing have traced the evolutionary pathway of modern immunoglobin back to sharks.

Immunoglobin D (IgD) is present in all jawed vertebrates, but its existence in acipenseriformes has previously not been proven. The acipenseriformes are fishes with a cartilaginous endoskeleton which are evolutionarily placed between elasmobranchs and teleost fish. The discovery of the IgD encoding gene in the Siberian Sturgeon (Acipenser baerii) bridges the gap in immunoglobin evolution between elasmobranchs and teleosts.  

A gene encoding immunoglobin W (IgW) has been identified in sharks, whilst the IgD encoding gene has been proved to be present in teleost fish. As IgW has previously been believed to be a homolog of IgD, this would indicate that the IgD found in teleost fish and mammals - including humans - can be traced back to the early evolution of sharks. However, without evidence of similar IgD genes in the intermediate phase between elasmobranchs and teleost fish, the evolutionary pathway could not be assured.

The researchers used polymerase chain reaction (PCR) and high throughput sequencing to identify the IgD gene in the acipenseriform fish A. baerii. The researchers found for the first time that the IgD encoding gene was expressed in the Siberian Sturgeon and furthermore that the gene shared features with that of teleost fish.

Immunoglobins (or antibodies) are key components of the vertebrate immune system and being able to trace the lineage of our own immune system back to sharks provides evidence that sharks have been an important evolutionary template for our own species as well as all fish and mammals which express this antibody.

Lin Zhu, Zhenxin Yan, Mengyang Feng, Dezhi Peng, Ying Guo, Xiaoxiang Hu, Liming Ren, Yi Sun. (2014) Identification of sturgeon IgD bridges the evolutionary gap between elasmobranchs and teleosts.  Developmental & Comparative Immunology. 42(2):138 

Shark Research - Small spotted catsharks are smarter than first thought

Researchers at Cranfield University have found that small spotted catsharks (Scyliorhinus canicula) exhibit cognitive ability with rapid learning skills. The experiment, led by Dr. Joel Cranfield, set out to assess the capacity for cognitive ability in sharks.

Cognitive ability is important for animals inhabiting changing environments such as the oceans - it facilitates memory and learning which improves the ability of an animal to catch prey or search for mates. Whilst marine mammals have been shows to possess cognitive ability, less is known about the capacity of sharks for learning and memory.

To assess the cognitive ability of the small spotted catshark, the researchers focused on the electroreception sense of the shark. Electroreception is an important sensory tool for sharks and rays; it allows them to detect natural electric fields such as those which might be given off by prey items. An assessment of the ability of sharks and rays to distinguish between electric stimuli given off by prey and that of an artificial object - such as undersea electric cables - will be valuable when assessing the impact these artificial electric stimuli may have on marine fauna.

The researchers split the sharks into 4 groups - those which would undergo positive reinforcement and would receive a food reward upon showing interest in an electrical stimulus and those which would not. After each group had participated in the experiment, the groups were switched so that the ones who previously received positive reinforcement no longer would and vice versa.

The researchers found that sharks conditioned to receive a food reward upon investigation of the electric stimulus were far more likely to return and bite the probe than those which had not received any reward, demonstrating rapid learning ability of this species. However when examining the ability of the sharks to retain this information as memory, the researchers found that the sharks possessed a memory of 12 hours to 3 weeks. The small spotted catfish inhabits mainly coastal waters which are highly variable and a memory of longer than 3 weeks may not be a survival requirement of this species. Therefore investigation into other, preferably pelagic shark species, may yield different results and potentially a longer memory time.

Kimber, J., Sims, D, Belamy, P. and Gill, A. (2014) Elasmobranch cognitive ability: using electroreceptive foraging behaviour to demonstrate learning, habituation and memory in a benthic shark. Animal Cognition. 17(1): 55-65