Friday, October 22, 2010

Swimming with Whale Sharks – Impact?

Manta Ray aggregation in Hanifaru - at risk!

Underwater Thrills alerts us to an interesting paper.


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


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.

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