White Sharks vs Sevengills - Paper!

First image of Sevengills on this blog = as always, great pic by Peter! Source.

Just in case you've missed it.
Watch.

I must say that I really like it.

Obviously, correlation is not causation so we'll never know 100% - but as somebody who has been equally documenting long-term changes in abundance that are likely partially due to competitive exclusion, I can only applaud the authors for advancing an astute and I believe highly plausible hypothesis.

But go see for yourselves.

Paper here, synopses here and e.g. here.

Enjoy!

Competitive Exclusion at Shark Reef - the Paper!

Thriving Sharks - still one of my very favorite pics ever, by one of my very favorite people!

Bless Juerg!

Despite of an ever increasing burden of obligations from his other activities, he has found the time to go and mine yet another data set from our monstrous data base.

So here are his latest insights!

Whereas the last paper (read it!) shows that feeding our Bull Sharks has no notable effects at the ecosystem level, this latest one documents the existence of small-scale effects, notably a progressive change in relative species abundance that as he postulates is likely due to a combination of competitive exclusion and gradual change of feeding protocols.

The general observation is this.

Over the past ten years, we've been seeing ever more Bulls (!), Whitetips and Blacktips and about the same number of Greys - but the number of Nurses, Lemons, Silvertips and Tigers has fallen precipitously.

And the possible explanations?

Juerg doesn't speculate, and a research paper is also the wrong forum for digressing into the minutiae of feeding protocols - but as I'm not being constrained by scientific rigor, allow me to elaborate some more.
Yes some of it is speculative and difficult to test - but having logged close to 2,000 Shark dives on Shark Reef, I would argue that it is at least plausible.

• Sharks don't generally like to approach people.
  Hence the necessity of using bait when diving where they don't aggregate naturally. Research has shown that at least the big, long lived species like Tigers are able to memorize the location (and possibly time) of successful feeding events - but the flip side is that they will likely stop bothering to pop by once they are not anymore being adequately rewarded.

• This may in part explain the decline in numbers of those intermediate Sharks.
  They occupy roughly the same depth profile as the Bulls and once the numbers of the latter did increase beyond some tipping point, the risk/reward ratio simply became too unfavorable - this especially for the Lemons and Silvertips who appear positively scared whenever I see them trying to sneak in, this quite possibly because they may well be on the Bull Sharks' menu.

• The Nurses are a different matter altogether.
  There, the principal factor may well be food composition and presentation, along with the fact that we don't feed them much as they create too much of a mess.
  
  Ever since taking on Shark Reef and turning it into a marine reserve, we've been concerned about our influence on the other Fishes. Having noticed an overabundance of small predators and scavengers, we've gradually phased out all Fish scraps and feed nearly exclusively Tuna heads, meaning that the overwhelming majority of bait leaves the reserve in the stomach of a large Shark or gigantic Trevally, as it should be. As a consequence, the Fish biodiversity of Shark Reef has undergone a massive increase from a baseline count of 260 species in 2004 to close to 500 in 2010 which is now highly indicative of a healthy Fish population on a Fijian barrier reef - possibly also because a robust Shark population may favor biodiversity, which would then be a positive small-scale effect!
  
  Those big Tuna heads are rather unattractive to the Nurses who have small mouths and got no means of cutting out adequate portions. And once we shifted to mid-water dumping as opposed to hand feeding in response to the increased numbers of Bulls, the Nurses were less able to monopolize bait on the bottom and may indeed have relocated to Lake Reef where protocols, I hear, are different.

• The Tigers?
  From my observations, they are incredibly persistent to the point of obstinacy - but they like to take their time and certainly don't appreciate the stress of having to contend with those frisky Bulls that have become ever bolder with increasing numbers.
  They certainly don't anymore slink away when the Tiger shows up like in the old times, but instead engage in direct competition to the point of where I dispose of footage of them out-swimming and even shouldering away the much bigger Tigers - meaning that in all likelihood, the latter have simply stopped bothering and prefer to try their luck elsewhere!
  
  And then, there is the fact that recently, the pressure by coastal fishermen on especially the particularly lucrative Tigers has increased substantially.
  If you add that to their risk of running into one of those Tuna longlines during their pelagic migrations, it is quite likely that the Tiger Shark population in Fiji has been depleted by overfishing!

• Not surprised about the Reefies.
  Like Juerg remarks, they nearly never descend to the lower depths and once there, they never attempt to feed, this likely owing to their inexistent chances of competing successfully for the bait but also, the risk of being predated upon by the Bulls. Conversely, we've conditioned the Bulls never to ascend to 10 meters, this also due to our positioning of the clients who obstruct any direct access to the feeder whereas the small Reefies can access him from the reeftop.
  Hence the Reefies are not subjected to competitive exclusion when they stay shallow.

• Generally speaking, resident Grey Reefie populations appear to be comprised of juveniles, subadults and adult females and are usually found at reef passes - but ours are predominantly adult males and thus quite possibly much more transient.
  This appears to be confirmed by the fact that they abscond for months on end in mid year, likely to go and visit one or more resident populations during the mating season, meaning that any newborns would reside there and not in the SRMR. With that in mind and considering the risk posed by the Bulls, they will continue to quickly dash in for a snack during meal times but otherwise remain rather wary and nomadic.

• The Blacktips took forever to accept any bait.
  If memory serves me right, they only started feeding and thus approaching people 6 years ago, and the increase in numbers may well be due to the fact that they are now swimming in from other areas, namely the lagoon side, of Shark Reef during feeding time, to then quickly abscond as soon as the feeding ceases. Like Johann teaches us, they migrate to breed in shallow lagoons, meaning that any juveniles would be found there. But they also disperse, meaning that some may have indeed hopped over from Serua Reef that features similar habitats - but my gut tells me that the majority are resident locals that have simply become bolder.

• And the Whitetips breed on Shark Reef.
  We know that because we've now observed neonates and juveniles on several years, and the population has increased accordingly - no unsolved mysteries there apart from the question of when we will reach carrying capacity and the population will stabilize.

There you have it.

There have been many changes, some of which massive - the question being, is it good or is it bad?

The answer is probably: rather good to indifferent!

Fish stocks are thriving, meaning that I cannot detect any evidence that those increased number of Reefies are having a negative effect - and when it comes to those other larger Sharks with larger home ranges, evidence suggests that they remain well protected within the Shark Corridor, this with the sad exception of those poor Tigers for whom we however carry no responsibility

And in the vicinity?

Yes like Juerg states, we don't quite know
But what we DO know is that the fishermen in Galoa catch more fish, this likely due to overspilling from the SRMR - whereas further away, stocks are grossly overfished and fishing yields have crashed. We also know that our big Sharks are not resident, meaning that we're not subtracting them from elsewhere where they continue to perform whatever functions they are meant to perform..

So with that in mind, how can I not be happy!

And as always, I'm mighty proud - and so thankful to Juerg for yet again a wonderful job in helping us better understand the animals we love and our influence on their life.

Merci Jürg - sisch jo wie immer e super gueti Sach!

Silkies vs Grey Reefs - Paper!

Source.

Very interesting!

Abstract here.

Juerg will be delighted.

He is currently formulating his newest paper that deals with the relative abundance of Sharks within Shark Reef, and this is really going to be helpful, albeit maybe more by juxtaposition that by analogy. 

We, too, have experienced notable changes over time but contrary to what has been observed in Jeddah where declines are being attributed to fishing, I believe that what we witness is the result of competitive exclusion, possibly coupled with the effects of the establishment of a (completely different) competing Shark dive in the near vicinity.

But that's for Juerg to analyze, so take it with a grain of salt.

And the other topics?

Boldness vs numbers.

Where our observations coincide is that like in the case of those Silkies we, too, observe an increase in boldness with increasing numbers, this certainly with respect to our Bull Sharks that have become positively pushy during the hand feed, forcing us to continuously adapt our procedures. 

At the same time, when away from the immediate feeding area, they however appear more habituated to humans insofar as they appear less reluctant to approach whilst at the same time behaving way more relaxed all the way to having practically stopped engaging in agonistic behavior like jerky swimming, gulping and bumping. Notable exception: our ever irascible Marlen who will immediately retaliate against any attempt at manhandling her!

This may possibly apply also to the Blacktip Reefies that from being frustratingly shy 10 years ago have become increasingly feisty - this with the caveat that although their numbers have certainly increased, this is most likely attributable to conditioning and learning.

Aggression.

I was intrigued by the observed lack of intraspecific and inter-specific aggression in the Red Sea - especially considering that the Grey Reefs are notorious!

Here, we clearly observe the latter whereby the Bulls will bite and hustle away other species, and when it comes to the former, we observe no overt aggression but never the less detect clear signalling of dominance, this usually by the larger and/or bolder individuals.

Individuality.

This once again confirms the findings of all Shark behaviorists and incidentally, all Shark divers that Shark behavior is context driven but also individually diverse - see also the other Silky Shark paper by the same Chris Clarke et al here that hypothesizes individually diverging foraging strategies.

And since yer at it, read this, too!

And there's a bonus point!

When googling the mysterious Danah Divers, Marine Research Facility, Jeddah, Saudi Arabia where Chris apparently acts as the Operations Manager, I stumbled across this remarkable story by Tom Campbell. So now you know how the SOSF has come about!

And incidentally, have a look at this - now THAT's what I call a dive boat!!! :)

But I'm digressing as always.

All in all, really very nice - kudos!

Shark Feeding - Part deux!

Helen and Fiji Bull Shark - pic by Michael Sealey of Biodiversidad Ibérica

Bless Helen!

Here is the second installment of her post.

I could not agree more - including the fact that there is a local effect, this however not so much precipitated by the bait that is actually all being eaten and mostly leaving Shark Reef in the stomach of the Bulls.which do not reside there. For them, those Tuna heads are just a snack, and not very nutritious at that, and I have no doubt that they continue to prey naturally and fulfill their ecological role in their habitat.

Like I said elsewhere, we are very mindful of our impact and have completely stopped any indiscriminate dumping of bait a long time ago. As a consequence, the composition of the Fishes has changed from a rather low species count of 260 that was being dominated by small scavengers and predators, to now 480+  that is highly representative of any (non-fished) fringing reef along one of Fiji's principal islands.

The effects I detect are more behavioral.

Juerg is writing a paper on the subject, so I don't want to preempt his findings on the subject, the more as I'm yet to see any draft. 

But apart from the obvious conditioning whereby we are actively teaching our Sharks to behave in certain ways, I believe that I'm observing inter-specific aggression all the way to competitive exclusion among the various Sharks. And also believe that we've interfered with the diel patterns of at least the Whitetips that are usually crepuscular but on Shark Reef, leave their hidey holes to come and feed at midday. 

But at this stage, I'm obviously speculating, and Juerg will also need to answer the question of so what - even if there's an effect, does that necessarily mean that it is bad?

Anyway, thank you Helen!

Her endorsement is far from trivial.

For years, Shark provisioning has been the target of much skepticism from researchers and NGOs alike, and only recently do I detect a slight shift in positions away from outright hostile to at least benevolently intrigued. This is largely due to the realization that baited Shark tourism, whilst certainly presenting its specific challenges (especially when conducted poorly!) is never the less  years ahead of the alternative = Shark fishing. 

And recent research is also showing that whilst local, hitherto unqualified and unquantified effects persist, effects at large temporal and spatial scales are negligible. 

Sharks, it appears, are just different.

Whilst bony Fishes show all the typical negative effects of conditioning that lead to the well known numerous bites by Groupers, Moray Eels all the way to those notorious swarms of pesky Sergeant Majors, Sharks simply don't do that - that is, provided that who feeds them does so responsibly, see the reports about beggar Sharks from, say, Tiger Beach!

Long story short?

Come and see for yourselves - this is still the top season for high numbers!

So, what are you waiting for!

David about Shark Feeding!

Great pic by Sasha - click for detail!

This was the first time I heard about David Diley.

Doug Perrine sent me the article and I thought, very cool - and the rest, as they say, is history.

And David is at it again!

Make yourself comfy, relax, take a deep breath and then read this post. It is as brilliant as it is long, meaning that you should really invest the time to read it in its entirety, and then probably read it once more - and no, I'm really not gonna weigh in, the more as BAD is being continuously mentioned as an example for best practice, which it frankly also is!

Plus, I don't advocate Shark feeding!

Surprised?

You shouldn't be. 

If you've paid close attention to this particular thread within this blog, I'm not at all of the opinion that it MUST be done. On the contrary, I'm very much of the opinion that nothing beats the awesome experience of witnessing Sharks doing their natural thing, like in, say, Palau, Malapasqua, the Sardine Run, Ningaloo, Fakarava or Cocos!

But of course those predictable natural aggregations are rather rare.

Plus, some of those Sharks are very shy, meaning that the encounters, although highly rewarding, can be very brief indeed.

Other than that, encountering Sharks in the wild is difficult for some species and all-but-impossible for others, meaning that in most cases, anybody wanting to showcase them to paying customers will have to resort to some form of baiting.

That's obviously what we do here in Fiji.

There, I'm of the opinion that it is neither harmful to the Sharks and their habitat nor to the humans, a fact that is increasingly being corroborated by recent research, this with the caveat that it only applies to large spatial and temporal scales.
But whereas there are certainly small scale effects like e.g. changes in species composition due to competitive exclusion by the boldest or most aggressive species, or the disruption of diel patterns in provisioned Sharks, there does not yet exist any substantiated evidence that those effects are harmful, at least not in the long term. That is, provided that there are some sensible protocols preventing excesses like those that have been recently documented for the Stingrays in Cayman!

As David correctly remarks, it's not so much about what the what but about the how!

But I said that I wouldn't weigh in.

Please go and read David's post.

Kudos mate, well said!

Sharks and MPAs!

Our Whitetip Reef Sharks - clearly resident and doing great. Stellar pic by Lill.

Nice to see our intuition confirmed!
It may sound trivial, but recent research finally confirms that Sharks thrive within Marine Protected Areas. There may be more, but these are the two new papers I know about.

Evaluating marine protected areas for the conservation of tropical coastal sharks.
Danielle M. Knipa, Michelle R. Heupel, Colin A. Simpfendorfer

Abstract

Global declines in shark populations have created uncertainty in the future status of many species and conservation efforts are urgently needed.
Marine protected areas (MPAs) are used increasingly as conservation tools around the world, but how they benefit mobile and wide ranging species like sharks remains unclear. To evaluate the degree of protection MPAs may provide for sharks, we used an array of acoustic receivers to examine the movements and spatial use of two tropical coastal species within two MPAs in the Great Barrier Reef Marine Park, Australia. Juvenile pigeye (Carcharhinus amboinensis) and adult spottail (Carcharhinus sorrah) sharks were fitted with acoustic transmitters from 2009 to 2010. Both species displayed long-term use of MPAs, with some individuals detected for longer than 600 days. The mean percentage of time C. amboinensis and C. sorrah spent inside MPAs was 22% and 32%, respectively. MPA use varied seasonally, with C. amboinensis spending a higher percentage of time inside MPAs in summer (mean = 28%) and C. sorrah spending a higher percentage of time inside MPAs in winter (mean = 40%). Although sharks used large areas inside MPAs, most individuals tended to use only half of the available protected space. In addition, all sharks made excursions from MPAs and individuals exited and re-entered at consistent locations along the MPA boundaries.
These results demonstrate that MPAs have conservation benefits for shark populations by providing protection across different species and life stages, and tracking studies can be used to help tailor MPA design to maximize effectiveness.

and

Reef Sharks Exhibit Site-Fidelity and Higher Relative Abundance in Marine Reserves on the Mesoamerican Barrier Reef
Mark E. Bond, Elizabeth A. Babcock, Ellen K. Pikitch, Debra L. Abercrombie, Norlan F. Lamb, Demian D. Chapman

Abstract

Carcharhinid sharks can make up a large fraction of the top predators inhabiting tropical marine ecosystems and have declined in many regions due to intense fishing pressure.
There is some support for the hypothesis that carcharhinid species that complete their life-cycle within coral reef ecosystems, hereafter referred to as “reef sharks”, are more abundant inside no-take marine reserves due to a reduction in fishing pressure (i.e., they benefit from marine reserves). Key predictions of this hypothesis are that (a) individual reef sharks exhibit high site-fidelity to these protected areas and (b) their relative abundance will generally be higher in these areas compared to fished reefs. To test this hypothesis for the first time in Caribbean coral reef ecosystems we combined acoustic monitoring and baited remote underwater video (BRUV) surveys to measure reef shark site-fidelity and relative abundance, respectively. We focused on the Caribbean reef shark (Carcharhinus perezi), the most common reef shark in the Western Atlantic, at Glover's Reef Marine Reserve (GRMR), Belize. Acoustically tagged sharks (N = 34) were detected throughout the year at this location and exhibited strong site-fidelity. Shark presence or absence on 200 BRUVs deployed at GRMR and three other sites (another reserve site and two fished reefs) showed that the factor “marine reserve” had a significant positive effect on reef shark presence. We rejected environmental factors or site-environment interactions as predominant drivers of this pattern.
These results are consistent with the hypothesis that marine reserves can benefit reef shark populations and we suggest new hypotheses to determine the underlying mechanism(s) involved: reduced fishing mortality or enhanced prey availability.

Very cool!
The latter paper is thankfully open access so you can read it in its entirety. There are also excellent synopses, one by Juliet right here and others here, here, here and here. What is particularly interesting here is the deployment of totally non-invasive bait cams and the correlation to the lack of fishing pressure (and thus, increased fish density) within the MPA.
Helen tells me that she has observed that Fish appear to know and take refuge within the confines of her Waitabu MPA, and from my days as roving underwater image hunter, I've learned to recognize whether a particular reef is being visited by spear fishermen by observing the behavior of the Fishes, particularly the Groupers - so it comes as no surprise that the Sharks who would be following their prey would also aggregate within the protected areas where they would be equally sheltered against any fishing pressure, find plenty of prey and thus thrive.

And what about the Shark Reef Marine Reserve?
Well we did set it up in the belief that in order to conserve a species one needs to preserve its habitat - but as always, it's complicated.
The Blacktip Reefs and Whitetips live, mate and give birth to plenty of babies right there so the conclusions of the papers are being fully confirmed.
Maybe even when it comes to the Grey Reefs but even there I'm less confident. From all I know, your typical resident aggregation of Greys consists of mature females plus juveniles and sub-adults of both sexes, whereas I thought that the adult males were non-resident and always roving, thus assuring gene flow - but on Shark Reef, most of the adults are males and then, like right now, we see a lot of juveniles. And in May/June, everybody leaves for a month or so, something we believe is correlated to mating opportunities somewhere else. But in reality, we don't quite know what's really going on there, so the whole scenario certainly warrants more investigation.
But when they are here they sure look perfectly happy!

The Silvertips, Nurses and Lemons?
As I stated somewhere else, they are increasingly being displaced by the assertive and ever more numerous Bulls, likely due to competitive exclusion - so although I'm sure that much like they've done in the past, they would love to turn up much more frequently, I equally fear that the deterrent is currently much too big for us to ever witness an improvement in numbers, MPA or no MPA.

And the Bulls and Tigers?
Mike's hypothesis stipulates much larger home ranges that have been confirmed by Juerg's telemetric studies - but they sure love to come visit for a juicy snack and maybe, even for some good company! :)

Anyway, all very interesting!

H/T: Demian and Rick!

Alex - back on Air!

Busy: Shark Reef in 2009!

Whilst I'm ruminating on one of those posts.

This one is easy.
Alex the Sharkman has not only revamped his website and started publishing his epic interviews, he has finally started blogging again.

His first proper post is about us.
To me, it is particularly interesting because so much has changed since, e.g. the fact that we don't anymore feed the Trevally at the surface and that the pit is now really out of bounds. It also reminds me painfully that none of the Tigers turned up for him, something that we interpret as competitive exclusion.

Anyway, it's a great read and a trip down memory lane.
What can I say but that we are really honored.
A big Vinaka Vakalevu my friend!

Enjoy Alex' post.

Congratulations Terry!

Bravo Terry Goss!

He has just won the Grand Prize in the Marine Photobank Ocean in Focus contest and will be visiting the Galapagos with a friend on a Lindblad Expeditions cruise. I did once join the venerable Lindblad Explorer ages ago and can attest to the fact that it will be the adventure of a lifetime!
Very, very cool indeed!

Very cool picture as well!
You can read more about it, and Terry in this interview and you can view more pics of the same Blue Shark on Terry's website. Terry is of course a veteran of the Shark Dive where he has been able to capture what remain some of the best shots ever of our Sharks, including this iconic portrayal of Scarface and Rusi.

Click for detail - seriously!

But that was ages ago!
Things have changed and we got more Sharks than ever, tho the visits by Scarface & Co are becoming ever rarer, likely due to competitive exclusion - in fact, we haven't seen Scarface all year and can only hope that she's embarked on one of her usual walkabouts like in the past!
Still, the dive is getting better and better, with Bull Shark numbers literally exploding!

Whatya think Terry - time for an encore?
And the answer to your question (just saw it now!) of course is yes in late May, early June! :)

Aliwal Shoal - What has happened to the Tigers?

Aliwal Shoal Tiger and diver, by DaWolf - a thing of the past? Notice the Blacktips in the background.

I must say, when it comes to SA, I remain of two minds.
Having been a staunch anti-apartheid advocate, I was overjoyed when the despicable regime finally disappeared. Mandela transcends positive attributes but then came the pathetic Mbeki - and Zuma, let alone Malema are frankly a disgrace and cause for grave concern.
When it comes to conservation, there is of course the brilliant terrestrial track record that on top of preserving vital unique habitat is contributing millions in tourism income. On the marine and especially, sharky side of things, not really impressed. There's certainly a lot of research, some of which is rather impressive; but when it comes to getting those Sharks protected, I see ALOT of self congratulatory media by the various bikini models, artists, sharktivists and whatnot - but in terms of having achieved tangible results?

The Shark diving Industry?
SA's Shark diving has been developed and very much put on the map by visionary, and probably equally crazy icons like Andre Hartman, and the legacy is being continued by excellent people like Mike Rutzen or Chris Fallows for whom I have nothing but the greatest respect. Other people, not so much - but such is the Industry everywhere, tribal and petty! Plus, news like these are of grave concern as such banana republic shenanigans will come at the direct expense of safety and reputation, and I'll leave it at that.

Anyway, I'm digressing as usual.
Why I'm writing this post is that this has piqued my interest.
Apparently, way less Tiger Sharks show up on the Aliwal Shoal dives. Apparently, the reason for this are poaching for trophies - and the highly controversial Shark nets.
This stuff: antiquated, ineffective, unselective, an ecological crime that needs to be stopped.



But is that the most plausible explanation?
Firstly, has anybody checked the data? Has anybody taken the time to go and corroborate those reports by talking to the KZNSB, by looking at fisheries data and by following up on the poaching allegations?

Secondly, Wolfgang reports that
The dive reports I received lately are alarming: Very few tiger sharks sightings, and the tigers don't stay, making one or two brief passes only to leave the scene altogether.

Hmmmmmmmm...
Sharks including Tigers don't like to approach people and that's why the dedicated Shark diving operators attract them with bait. In Aliwal Shoal, this is now thankfully done with ZIBS, a Shark friendly implement that is however not dispensing any food. Thus the Sharks are being teased in and then waste time and energy that could be spent on productive hunting, which is however not the topic here.
The topic is that this could well lead to negative reinforcement whereby individual Sharks wise up to the fact that they're being cheated and learn to avoid that situation.
And then, there are the notorious swarms of Shark hugging bimbettes and intrepid freedivers abusing the Sharks as underwater scooters: do you really believe that those disrespectful stupidities are in any way conducive to those animals ever wanting to come back?

Which brings be straight over to the following.
In my experience, Tigers are rather placid (and incredibly determined!) and just want to do their thing in peace without being harassed.
Juerg has been here for a lightning fast go-see and informs me that his next paper is about to get published. In it, among other topics, he documents how other Shark species have reacted to the stupendous increase in our population of Bull Sharks that has culminated in our sighting of approx 100 individuals this June - and counting, next year there will be more!
I don't want to pre-empt his conclusions but one of the results will be that we're seeing less Tiger Sharks. From my personal observations, this is because they just cannot be bothered to come and join the fray in order to compete with the Bulls - this the more as the Bulls are clearly not intimidated and on the contrary, have even been observed to shoulder away the Tigers when getting to the bait!
Talk about a total lack of respect!

And then,there's the famous Shark Rodeo in Walker's Cay.
As far as I know, only a very few of the famous Bulls bothered to ever turn up at the chumsicle and when they did, they made one or two brief passes only to leave the scene altogether. Tigers, a big fat zero - and this despite being frequently sighted in the vicinity, despite of the yummy fish smell and despite of the massive commotion caused by the Caribbean Reefs and especially, the Blacktips!

Or maybe because of it!
Blacktips are your quintessential asshole Shark: lightening fast, frisky, in-your-face assertive and unpredictable - certainly nobody any self respecting Tiger Shark would ever want to be associated with, especially if they came in packs!

May it be that the exact same is happening in Aliwal Shoal?
May there have been an increase in Blacktips? May there be some correlation between that increase and the decrease in Tiger Shark sightings? May Tiger Shark diving in Aliwal Shoal have become the victim of its own popularity - among humans but above all, among Blacktip Sharks?
Some form of interspecific exclusion, competitive or not?

Yes I'm clearly speculating - but has anybody looked into it?
Thing is, I fully support Wolfgang's cry for better coordination and better Shark protection in SA - tho I fear that achieving any degree of co-ordination, let alone cooperation will be difficult (...) and that in view of the current banana republic shenanigans, few operators will have the guts to speak up against the inept Government policies. But, as always, all should happen based on factual data - and when it comes to those Tiger Sharks, I'm not that sure.
Thoughts?

And since we're at it:
Tiger Beach? Feisty Lemons vs placid Tigers?
Questions questions... :)

Swimming with Whale Sharks – Impact?

Manta Ray aggregation in Hanifaru - at risk!

Underwater Thrills alerts us to an interesting paper.

ABSTRACT

1. The whale shark (Rhincodon typus) is a popular focal species within the global marine tourism industry. Although this has contributed to increased protection being granted to the species in several countries, tourism itself can be detrimental to the sharks in the absence of appropriate management. Potential impacts can be mitigated, at least in the short term, by adherence to well-designed interaction guidelines.

2. A burgeoning marine tourism industry based on swimming with whale sharks has developed at Tofo Beach in Mozambique. However, no formal management is currently in place at this site.

3. The behaviour of whale sharks during interactions with boats and swimmers were recorded during 137 commercial snorkelling trips run from Tofo Beach over a 20 month period. Whale sharks were encountered on 87% of trips, which operated year-round.

4. Boat proximity and shark size were significant predictors of avoidance behaviour. No avoidance responses were recorded at more than 20m boat distance.

5. The mean in-water interaction time between sharks and swimmers was 8 min 48 s overall. There was a significant decrease in interaction times during encounters where sharks expressed avoidance behaviours, and also in cases where sharks had expressed boat avoidance behaviour before swimmers entered the water.

6. It is suggested that mean encounter times can be extended through adherence to a basic Code of Conduct for operators and swimmers that enforces minimum distances between the sharks, boats and swimmers. Using encounter time as a measure of the ‘success’ of interactions holds promise, as longer encounters appear to be indicative of lower impacts on sharks while also providing higher customer satisfaction for swimmers.
Copyright r 2010 John Wiley & Sons, Ltd.

From the paper

DISCUSSION

Whale sharks were sighted in every calendar month, confirming Tofo Beach as having one of the few known year-round aggregations of the species.
There was some observational evidence for seasonal variation in shark abundance, with a September/October peak. However, as trip distance and duration – and therefore the total number of whale sharks encountered – varied according to the length of tourist interactions with individual sharks, detailed analysis of seasonal abundance awaits a more standardized approach.

The overall success rate of tours, i.e. where one or more sharks were sighted, was 87.0% over the study period.
This figure is higher than the seasonal sighting rates at Ningaloo Reef in Western Australia (81.6% between 1996 and 2004) (Mau and Wilson, 2007) and Gladden Spit in Belize (69% between 1998 and 2003) (Graham and Roberts, 2007). The mean number of whale sharks encountered per trip at Tofo (3.0) was higher than the mean number of interactions recorded per trip at Ningaloo between 1996 and 2004, which was 2.6 initially, declining to 1.2 during the period of that study (Mau and Wilson, 2007). This is a notable point, considering that snorkelling trips at Tofo utilize boat-based searches along a relatively small length of coast, whereas in Ningaloo spotter planes are employed to locate the sharks over a broader area (Mau and Wilson, 2007). The number of sharks encountered per trip during September and October at Tofo were similar to in-season rates at Donsol in the Philippines (6.6 and 8.15 interactions per trip in 2004 and 2005, respectively) (Quiros, 2007) and Gladden Spit (2 to 6 sharks per trip between 1998 and 2003) (Graham and Roberts, 2007).

The high trip success rate and mean number of interactions observed over the period of the present study suggest that Mozambique has considerable potential as a whale shark tourism destination, with a ‘product’ that rivals or exceeds more established whale shark tourism destinations. These results also support aerial survey data from the South African and southern Mozambican coasts that had previously recorded relatively high numbers of whale sharks close to Tofo (Cliff et al., 2007).

Customer satisfaction with in-water interactions with dwarf minke whales (Balaenoptera acutorostrata) in Australia was significantly associated with the duration of the encounter
(Valentine et al., 2004), and the same appears to be true for swimmers with whale sharks (Catlin and Jones, 2009).
In the present study, the expression of short-term avoidance behaviour by individual whale sharks was linked to a reduction in encounter time. Therefore, encounter time appears to have potential as a crude measure of the overall ‘success’ of interactions. For the purposes of the following discussion, it is explicitly assumed that the primary aim of any management intervention will be to maximize encounter times, which is most easily achievable through the minimization of avoidance behaviour.

A significant link was found between the expression of avoidance behaviour by sharks and the proximity at which swimmers entered the water from the vessel.
Boat avoidance behaviour was also associated with shorter encounter times during ensuing in-water interactions with individual sharks.

This suggests that disturbed sharks either have a heightened stress response, or in some cases dived before a close interaction with swimmers could take place. Martin (2007) suggested that boat avoidance behaviour in whale sharks may be related to either the low-frequency noise signature of the motors or to a perceived potential for boat strikes. Scars from small boat strikes have previously been recorded from Mozambican whale sharks (Speed et al., 2008), although the observed frequency of occurrence at Tofo was considerably lower than that reported from other aggregation sites (Cardenas-Torres et al., 2007; Rowat et al., 2007). The presence of scarring was not identified as a significant predictor of avoidance behaviour in the present study, although this analysis did not specifically examine injuries from boats.

Boat avoidance behaviour was not observed at (estimated) distances larger than 20m in the present study.
These data suggest that this distance represents a useful initial value for a boat exclusion radius around sharks. This recommended distance considerably exceeds the present mean swimmer discharge distance of slightly over 7m, suggesting that training programmes will need to be implemented for skippers and guides to ensure changes in current behaviour. Given that a reduction in boat avoidance behaviour is likely to significantly increase mean in-water encounter times overall, the application of this new exclusion distance should be emphasized in training.

There is no internationally-applied boat exclusion radius in use at present, as the situations and practical realities differ between sites.
Code of Conduct recommendations around the world vary from 5m in Bahia de los Angeles, Mexico (Cardenas-Torres et al., 2007), to 10m in Yum Balam, Mexico (Remolina et al., 2007) and 30m in Western Australia (DEH, 2005). Furthermore, the high frequency of avoidance behaviour exhibited by sharks when interacting with more than one boatload of swimmers clearly suggests that, as laid out in most national Codes of Conduct, only one boat should be ‘in contact’ with a shark at one time, whilst any others maintain a reasonable distance (i.e. outside the proposed 20m exclusion radius).

Swimmer interaction times recorded in the present study represent an intra-site baseline value for future adaptive management measures.
Inter-site interaction times are likely to be less useful to the formulation of Mozambican management procedures, as shark behaviour is likely to change according to feeding strategy and the specific characteristics of each location. For example, the average length of interactions in the Philippines, where a higher proportion of sharks were feeding while observed (in 2005), was only 3 min (Quiros, 2007). Conversely, mean interaction times at Ningaloo Reef declined from 27 min in 1996 to 7 min in 2004, although some interim years remained high, with the decline possibly influenced by changes in operator procedures (Mau and Wilson, 2007).

Although data on swimmer behaviours were not collected in the present study, other studies have shown that maintaining a distance of 3m from the body of the shark and 4m from the tail result in a reduction of avoidance by sharks.
These distances minimize the potential for accidental touching and also reduce swimmer perceptions of crowding, thereby improving the quality of the encounter. Underwater visibility is generally high enough at Tofo to make these distances practical, unlike in Mexico and the Philippines where visibility is often poor. In the current study, however, the physical number of swimmers in the water had no apparent effect on encounter length, although the mean number of swimmers was higher than that recommended by most Codes of Conduct (Quiros, 2007; Remolina et al., 2007; Catlin and Jones, 2009). It seems likely that, rather than the sheer presence of swimmers, their behaviour and proximity to the shark is the important factor to consider in future studies and management assessments.

Sea surface temperature was a significant predictor of avoidance response, with higher temperatures associated with decreased encounter times.
As the metabolic rate of ectothermic sharks are strongly affected by ambient water temperatures (Carlson et al., 2004), this result may suggest that whale sharks swim faster or are more responsive to swimmer approach under warmer conditions.

Although the results of the present study show that an unmanaged tourism industry in Mozambique could have the potential to cause short-term behavioural modification in whale sharks, basic mitigation measures should be relatively simple to implement.
The results as shown can reasonably be taken to approximate the natural behaviour of skippers and guides, as no formal interaction guidelines were in place during the study. An increased effort to educate front-line operators in appropriate interaction techniques is therefore integral to the success of any new management strategies. Experience from other countries has shown that instituting accountability procedures for these staff members is also an important element, as even relatively low levels of non-compliance can lead to negative short-term behavioural impacts (Quiros, 2007).

Recent studies from Ningaloo Reef in Australia (Meekan et al., 2006; Holmberg et al., 2008, 2009), Mahe in the Seychelles (Rowat et al., 2009) and Gladden Spit in Belize (Graham and Roberts, 2007) have demonstrated that whale sharks can be temporarily resident or show fidelity to feeding sites.
This suggests the potential for sharks to be repeatedly exposed to tourist operators, which could result in cumulative impacts. Quiros (2007) found that sharks sighted for the first time at Donsol were significantly more likely to exhibit avoidance behaviour when interacting with swimmers than sharks encountered repeatedly, which suggests that some degree of habituation may occur.

However, results from long-term studies on bottlenose dolphins suggest that in some cases, rather than becoming habituated, sensitive individuals may simply leave the area (Bejder et al., 2006a,b).
This can lead to long-term population declines even in the absence of obvious short-term behavioural modification (Bejder et al., 2006a,b). Given that the length of coast where tours are conducted in Mozambique is relatively small, a large proportion of sharks utilizing this area are likely to be exposed to tourism. This could exacerbate the potential for negative impacts on Mozambican sharks and highlights the importance of ongoing monitoring to assess the medium- to long-term impacts of tourism on whale sharks in this area.

Mozambique plans to attract 4 million tourists annually by 2020 (Ministerio do Turismo, 2004).
Such increasing tourist numbers make it vital to introduce active management for Mozambique’s whale shark tourism industry to ensure high quality experiences for swimmers while minimizing detrimental impacts on the sharks. The Mozambican government is presently focused on poverty reduction rather than environmental sustainability. Consequently, realizing the potential non-consumptive economic value of whale sharks is likely to be an important management consideration.

However, if this vision of sustainable growth is to be achieved, iconic tourist species such as whale sharks require enhanced protection and a dedicated management strategy.

Simon needs to be commended.
I’ve mentioned him and the Foundation for the Protection of Marine Megafauna here and it’s great to see how he is directly applying his research to the challenge of developing a long-term sustainable ecotourism industry in Mozambique. Let's hope that the powers that be get to read the paper and follow the recommendations!

And if not?
A while ago I blogged about the Athropogenic Allee Effect in ecotourism, i.e. the risk of contributing to the demise of charismatic endangered animals by showcasing them to the public at large, and it just so happens that David over at Southern Fried Science is exploring a specific facet of this issue in his latest ethical debate .

It really is a difficult one.
Predictable encounters with Sharks have undoubtedly contributed enormously to changing perceptions and to creating a legion of Shark lovers and a plethora of pro-Shark initiatives. But it has come at a price: over the years, I’ve witnessed the demise of several iconic Shark hotspots– and when it comes to some of them, I harbor the strong suspicion that the main cause for the disappearance of the Sharks was not the Shark fishermen, but the divers themselves!

Take for instance Ras Mohammed : still a terrific, and highly challenging dive – but the hundreds of Reef Sharks one used to encounter on every dive have moved away as the cattle diving boats have moved in.
Having said that: interesting video!



Or, closer to the topic at hand: take Richelieu Rock .
When it was discovered by two of the local liveaboards, Whale Shark sightings were so predictable that the day boats out of Phuket had a money-back guarantee. Then, the number of cattle boats exploded, the site became swamped and although the rock continues to be a world class macro dive, the Whale Sharks are largely gone.

To me, the interesting aspect is this.
These were not the much maligned baited dives with predatory Sharks: these were so-called natural encounters, much like what people experience in Cocos and in the Galapagos. And yet, it appears, the problems were very much the same : multi-user sites, lack of uniform and animal-friendly protocols, and competitive pressure all the way to outright greed on the side of the operators who are often unable or unwilling to cooperate and self-regulate for the common good, coupled with lack of rules and enforcement by the regulator.
Sound familiar ?

Whale Shark swimming shares many aspects with Whale watching, to the point that much of the research into the implications of the relevant ecotourism industries can be cross-referenced.
One of the generally accepted tenets in both activities is that SCUBA diving is being frowned upon as the bubbles are supposed to spook the animals. That may be true but the flipside is that chances for encounters are really only limited to those incidences where the animals tolerate, or even welcome the presence of divers – much to the contrary of snorkelers who being way more agile, can much more easily be driven to, approach and keep pace with the animals - and thus harass them!
Add that to the above-mentioned problems, and you have the recipe for certain disaster!

Case in point: look no further than Vava’u, Tonga.
To this day and after seventeen years of Whale watching, the industry remains the poster child of how NOT to do it, and of everybody loosing out as a consequence. No, I won’t dwell – though having lived there, I certainly could! Suffice to say that I will only recommend my good friends Paul and Karen of Dive Vava’u , the friendly ladies of Endangered Encounters and very grudgingly as I really neither like nor respect the owners, Whale Watch Vava’u.

Whale Sharks and Mantas?
Read this: simply shocking, especially considering that Hanifaru could so easily be the very best site in the world - the more as everybody knows the solutions!
Should you really have the patience to labor through it: check out this remarkable piece about Whale Shark swimming in Mexico. It is thankfully open access and a great case study of two adjacent but different sites and starting on plate 167, it contains a whole list of recommendations that could easily be adapted to other situations – and guess what, it ain’t rocket science but nothing but good old fashioned common sense instead!

In essence, the only viable solution is this.
If the industry cannot self regulate - and it rarely can, especially when it comes to multi user sites: then government as the resource owner has to step in and regulate it, by defining protocols and penalties for breaching them (!), by monitoring and enforcing compliance, and by regulating growth via a licensing system. All of this has to happen based on the best available research data. And of course: whenever possible, full protection and a user fee to compensate and also, to re-train the stakeholders, foremost of which the fishermen!
This is why Cocos and the Galapagos work, albeit in a sub-optimal way, and other places are at risk!

So, here’s to Mozambique implementing the right procedures.
But when I read that The Mozambican government is presently focused on poverty reduction rather than environmental sustainability, I am highly alarmed. Such policies are of course laudable but at the same time, without a focus on sustainability, they are doomed to fail in the long term. Look at the over-harvesting, the associated cost (!) and the subsequent collapse of fisheries, especially in the lesser developed nations and you can see where I’m coming from.

As always, we shall see.
Both sites, Mozambique and Hanifaru, have excellent potential to become iconic tourism hot spots and if properly managed, to provide for sustainable incomes and poverty alleviation for countless generations to come.
Fingers crossed that the authorities will take the right decisions.