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,