Lemon sharks benefit from Marine Protected Area in Turks & Caicos

You may be forgiven for thinking that the creation of a marine protected area (MPA) would obviously lead to a greater abundance and diversity of marine life within the MPA as oppose to outside it's boundaries. However whilst creating marine reserves does typically lead to a greater density and size of organisms within the reserve boundaries, it is not to be assumed that this will be the case and until the particular reserve has been assessed it's success may largely be unknown.

In 1992, Bell Sound Nature Reserve (BSNR) in the Turks and Caicos Islands was established with a view to protect juvenile bonefish which are targeted in the Turks and Caicos Islands. A team of shark researchers led by Aaron Henderson from the Center for Marine Resource Studies in South Caicos have investigated whether this MPA is also having an effect on populations of the lemon shark (Negaprion brevirostris).

Lemon sharks are classified as Near Threatened in the IUCN Red List as they are caught in both commercial and recreational fisheries; as yet no management plans have been put in place to protect these sharks.

The researchers observed higher numbers of lemon sharks within BSNR than in the waters outside the reserve. Lemon sharks do exhibit a preference for shallower water and so the increased quantity of sharks within BSNR could be owing to habitat selection rather than protection from fishing, however he researchers surmised that the protection from predation offered by the MPA was attractive to the sharks and could cause them to want to remain in the reserve as oppose to moving outside.

Whilst the reasons for the higher number of sharks inside the MPA as oppose to outside is not yet entirely clear, the conclusions drawn were that BSNR is important to the local juvenile lemon shark population.

Shark teeth could pave the way to new dental therapies for humans

Whilst humans might be able to make do with a set of false teeth once the two sets we have during our lives have worn out, tooth loss is more critical amongst the rest of the animal kingdom. Elephants, for example, have 6 sets of replacement molars and once they have all been worn down the animal will die from starvation - a major cause of death in mature elephants. Sharks however, have developed a strategy to deal with the problem of tooth loss and that is to have unlimited sets of new teeth during their lifetime - something which most other vertebrate lineages have lost.

The genetic basis for tooth regeneration in sharks has recently been investigated by scientists at University of Sheffield using the catshark (Scyliorhinus spp.) as a model. The research indicated that the ancestral condition of vertebrates was likely to be that of constant tooth regeneration and that tooth development in vertebrates is governed by a core set of genes. The team discovered several potential reasons why sharks are able to produce unlimited sets of replacement teeth: firstly having a jaw made of cartilage as oppose to harder, bony material allows new teeth to constantly move forward replacing older, worn out teeth. Secondly sharks have an expanded dental lamina which houses multiple sets of teeth ahead of being required and the team suggests that this is essential for continuous tooth regeneration.

What is significant about these findings is how similar this core set of genes governing dental development is between sharks and our own species; in fact many of the genes which govern tooth development in vertebrates have thought to have remained unchanged for around 450 million years. The research suggests that slight genetic changes to this gene set could be the key to unlimited tooth regeneration as oppose to a finite set of teeth. Understanding how this gene set functions across the vertebrate lineage could contribute to the development of novel therapies for tooth loss in humans.

Rasch,L.J.,et al., An ancient dental gene set governs development and continuous regeneration of teeth in
sharks. Dev.Biol.(2016) http://dx.doi.org/10.1016/j.ydbio.2016.01.038i

Predator and prey - even a whale shark isn't too much for a great white!

It seems as though great white sharks (Carcharodon carcharias) are not adverse to taking on prey much bigger than themselves as two whale shark (Rhincodon typus) centra have been found amongst the stomach contents of a great white.

The centra - the central part of a vertebra - were removed from the stomach of a 4.5m long white shark which was caught in the 1960s at Cheynes Beach Whaling Station, Western Australia. The vertebrae remained at the Western Australian Museum until they were re-examined after a chance visit by Dr. Michael Newbrey from the Royal Tyrrell Museum of Palaeontology in Alberta, Canada. Dr. Newbrey immediately identified the vertebrae - which had been mis-labelled all those years ago as belonging to a Basking Shark (Cetorhinus maximus) - as those of a whale shark. Based on the size of the centra, the individual they belonged to would have been at least 8.5m long.

The find raises a series of interesting questions. First of all, the ranges of the white shark and the whale shark do not commonly overlap; white sharks - whilst having a circumglobal distribution - prefer temperate waters whilst whale sharks are found in tropical and warm temperate seas. Secondly, did the white shark attack a live adult, whale shark or did it ingest the centra whilst scavenging from an already dead whale shark? White sharks are known to eat other elasmobranchs and have been observed feeding on dead baleen whales in certain areas so it is not out of the question that the whale shark was deceased by the time the great white came to feed on it.

Whilst we may never know the fate of the two sharks in this story, this new discovery is the first confirmed proof that white sharks will eat adult whale sharks, and that even the largest fish in the ocean is not safely off the menu for the worlds greatest predator (in this writers opinion :)

Read the article here
Glenn Moore's Blog @Western Australian Museum

The 2015 Worldwide Shark Attack Summary is out!

According to the 2015 Worldwide Shark Attack Summary of the International Shark Attack File (ISAF), 2015 saw a record high number of unprovoked shark attacks. Out of a total of 164 recorded attacks, 98 were categorised as unprovoked; this figure surpasses the previous highest number of 88 unprovoked shark attacks in 2000.

However, before you go grabbing your speargun and practising the line "Smile you son of a bitch", it's important to point out that whilst the number of unprovoked attacks has risen in 2015, the overall rate of attacks could very well have remained unchanged or even fallen. The researchers who curate the ISAF attributed the increase in shark attacks to more humans in the water and better reporting of shark attacks rather than an increase in the rate of shark attacks. The researchers also caution against putting too much faith in short term trends owing to year to year variability of environmental conditions which can affect shark populations.

Of the 98 unprovoked shark attacks in 2015, there were only 6 fatalities worldwide and long term trends indicate that the rate of fatalities owing to shark attacks is decreasing. Whilst news of shark attacks will always draw media attention and excitement, the numbers pale into insignificance when compared to the 1.24 million people who were reported to have been killed in road traffic accidents in 2010.

Geographically the majority of the shark attacks occurred in North American waters, with Australia coming a close second with 18 unprovoked attacks - 1 of which was fatal. People participating in activities which caused a lot of surface turbulence such as surfers were the most vulnerable to attack whilst snorkellers constituted only 9% of the number of people attacked. There were no reports of unprovoked attacks on scuba divers in 2015.

The ISAF has been run from the Florida Museum of Natural History since 1988 and is the longest running database on shark attacks globally. As well as curating worldwide shark attack information, the ISAF also provides regular advice on shark attacks issues.

Sustainability of shark fisheries on the Great Barrier Reef

The Great Barrier Reef Marine Park (GBRMP) is known worldwide as a natural wonder: a protected underwater haven for tropical fish, sharks and other marine fauna. However, only 33% of this marine protected area is closed to commercial fishing activities - within the rest of the park commercial fishing boats are allowed to operate and to carry out large scale fishing activities such as trawling and gill netting.

This is not to say that these activities are allowed to happen unchecked, however. Commercial fishing within the park operates under strict zoning rules and, as with most commercial fisheries there are maximum fishing quotas and possession limits in place.

The difficulty with any type of commercial fishing activity is assessing whether the existing marine populations truly can bear the brunt of the fishing activity. The ocean is a huge area and species are typically wide ranging, making accurate assessment of animal numbers difficult.    

In recent study published in Fisheries Research a team of researchers have discovered that some commercial fishing activities within the GBRMP may not be sustainable.

The study focused on tagging and assessing the three most commonly harvested sharks in the GBRMP: the Australian blacktip shark (Carcharhinus tilstoni), the Spot-tail shark (Carcharhinus sorrah), and the Spinner shark (Carcharhinus brevipinna). The Pigeye shark (Carcharhinus amboinensis) and the Australian Sharpnose shark (Rhizoprionodon taylori) were also included as two example of non-target species. In total, 3,413 sharks were tagged during the course of the study.

Whilst the team discovered that harvest rates were highest for the Pigeye shark it was summarised that the numbers were still around the acceptable optimal equilibrium harvest rate for this species. Only a small amount of the population of this stock were vulnerable to commercial fishing activity and therefore the species may be able to withstand greater fishing pressure. However such high harvest rates for this species are surprising as it is not a target species and is instead being caught as bycatch by fishing boats.

The more worrying outcome of the study was that whilst the annual harvest rate was lower for Australian Blacktip sharks than for Pigeye sharks, the current level of exploitation of this species could be too high. This is owing to 2 main factors: the population of Blacktip sharks in the GBRMP is thought to have a lower reproductive rate than populations from northern Australia making it more difficult for stocks to replenish themselves, and this species is available to commercial fisheries from age 0 meaning that all of the population can be fished at any stage of their life cycle.

Whilst these findings can only make assumptions about localised depletion of the study species within the GBRMP, the results are important and further research and monitoring is essential to ensure that fish stocks remain healthy in this marine protected area.      

Harry et al. (2016) Assessment of a data-limited, multi-species shark fishery in the GreatBarrier Reef Marine Park and south-east Queensland

The Sharksafe barrier - an ecological way to keep sharks away from beaches!

The Sharksafe barrier has been causing quite a bit of fuss amongst shark enthusiasts as it has been promised to provide an environmentally friendly way to exclude sharks from swimming beaches. Now it's success has been proven as a team of researchers has successfully tested the barrier with live sharks. 

Currently, shark netting (where nets are strung close to swimming areas to try and protect the public from sharks) is in effect in New South Wales and Queensland in Australia and Kwa-Zulu Natal in South Africa. Existing shark nets do not simply exclude sharks from swimming beaches; instead the intention is that the sharks will become entangled in the nets and die. The impact of shark nets is not limited to sharks either as dolphins, dugongs, turtles, whales and other marine fauna are often found dead in these nets (if you are interested in reading an in depth analysis hop along to The Shark Post - The Truth About Shark Nets). As well as shark netting, governments sometimes employ other techniques to try and reduce shark attacks near public beaches such as drumlines or shark culls. 

None of the activities above are successful in completely excluding sharks from the waters around public beaches, and they have all have a detrimental impact on other marine fauna. 

In their work the researchers deployed the Sharksafe barrier around Gansbaai, South Africa - a region commonly populated with Great White Sharks (Carcharodon carcharias). The barrier was equipped with artificial kelp and electro-sensory magnets to see if these additional stimuli would elicit further changes in the swimming behaviour of the great whites. Great whites have been observed to show reluctance to enter kelp forest and the researchers had success with repelling bull sharks with magnets in previous studies (The Shark Post - Magnets could be used to successfully repel bull sharks).

The Great Whites showed a strong aversion to swimming between the regions with additional stimuli and a general avoidance of the Sharksafe barrier. In addition to this the barrier is ecologically friendly as no changes to the behaviour of the Cape Fur Seals which inhabit the area was noted, and unlike shark nets marine animals will not get entangled in the more rigid structure of the Sharksafe barrier. 

Whilst further studies will be needed to see the best way to utilise the barrier to ensure total exclusion of Great Whites from swimming beaches, these results are positive and lend hope to a more ecological friendly way to ensure swimmer safety in the future.      

Connell, C., Andreotti, S., Rutzen, M., Meyer, M., Matthee, C. and He, P. (2014) Effects of the Sharksafe barrier on white shark (Carcharodon carcharias) behavior and its implications for future conservation technologies. Journal of Experimental Marine Biology & Ecology. 460.

Mick Fanning's media feeding frenzy - who's the real victim here?

Earlier this week my newsfeed was inundated with posts about Mick Fanning's recent encounter with a shark in South Africa, For those who might have missed it, 3 times surfing champion Mick Fanning was competing in the J-Bay Open surfing competition in South Africa when a shark popped up next to him and snagged his leash. As the shark dived, the leash was broken and Mick was knocked off his board; he was picked up by rescue boats which were laid on for the event and whisked off to safety. You can review the whole thing here.  

Whilst a shark popping up at a pro surfing event is most definitely news worthy, the real news in this story is how sensationalised this event seems to have become. Once again the media appears to have taken this as an opportunity to showcase sharks in a bad light. The Australian reported that a "large shark stalked and attacked" the champion surfer, The Guardian claims that Fanning "fought off a shark attack" whilst a host on Fox News suggested that officials should be clearing the waters of sharks before an event of this nature!

It may feel as though these over hyped media pieces are all just a bit of fun but in reality they are having a detrimental effect on how the world views sharks. At a time when global shark populations are so vulnerable owing to over fishing and hunting for shark fin soup, shark conservation needs all the public support it can get. Journalists should also have a moral responsibility to report accurately on events, instead of sensationalising their articles in an attempt to get newspapers off the shelf.    

Whilst accurate global shark attack statistics are tricky to pin down, the Department of Ichthyology at the Florida Museum of Natural History is attempting to do so with their International Shark Attack File. In 2014, they documented just 3 fatalities from unprovoked shark attacks - and whilst that may seem like 3 too many, if you compare this figure to fatalities from road traffic accidents, alcohol or tobacco, the risk of dying from a shark attack pales into insignificance. Yet most people's perception of the risk of being killed by a shark is much higher owing to the poor media image given to these animals. 

In fact, the bad light cast on sharks by the media is so detrimental to their conservation that researchers at the University of Sydney and the Mote Marine Laboratory's Center for Shark Research in Florida have now proposed a new classification system to describe all shark interactions. Currently the majority of news articles which involve sightings or encounters with sharks will be touted as an "attack" - even if the shark simply swims up to someone then swims away. For the sake of accurate reporting, the Neff-Heuter study group has proposed 4 new terms to be used for all shark encounters: Shark sightings, Shark encounters, Shark bites and Fatal shark bites. In this way they hope to separate fact from hype and ensure that the public gets the most accurate record of events.  

Thankfully the majority of people who use the oceans - divers, surfers, swimmers - recognise that we are the visitors in the shark's world and are advocates for protecting the marine environment - including the species which live there. This still doesn't excuse sloppy media reporting and an attempt to villify a group of species simply to sell papers.