Sunday, July 31, 2016

Braving the Waters of Bimini!

Jillian and Dunc - they don't come much nicer than this! Source.

Jillian is one of the good ones, and this is really nice.

Fakarava - Inverted Trophic Pyramid?


Remember Michael Domeier's comment to this post?
Turns out that the man was prescient - and this literally: being one of the authors, he undoubtedly knew that this was coming!

The paper is here - read it!
And here and here are some synopses - and since I find them partially misleading, here's what I understand.
  • Fakarava Atoll has two main passes, Garuae in the North and Tetamanu, where this research happened, in the South.
    Like in other atolls in the Tuamotu archipelago like e.g. the spectacular trou au requins in the pass of Apataki, they are home to aggregations of resident (and semi-resident) Grey Reefie comprising, if memory serves me right, adult females and numerous juveniles/subadults of both sexes. The passes are great Reef Shark habitat because the Sharks can remain quasi-stationary by lazily riding the currents whilst engaging in ram ventilation, and because especially Tetamanu with its comparatively mild currents supports a good numbers of resident Fishes and acts as a migratory corridor for other prey species that regularly enter and leave the lagoon in line with the tides and the seasons.

  • Yet, the researchers postulate that since the pyramid of productivity inside of Tetamanu is inverted, the available prey biomass would not be sufficient to sustain even only the local population of highly resident Sharks. This means that in order for the Sharks to be able to reside there without having to forage farther afield, their food/energy requirements would somehow need to be subsidized.

  • That subsidy happens over several months during the Austral Winter.
    Then, huge numbers of several species of bony Fish successively aggregate in the passes in order to spawn = in essence, as the prey representing the productivity of the adjacent lagoon travels to the Sharks, the Sharks don't have to travel to the prey.
    This opportunity attracts the majority of transient Reefies (= likely the adult males) along with the less resident ones, meaning that the Grey Reef concentration in Tetamanu nearly triples. Still, during that time, the biomass of prey is vastly larger than that of the Sharks and all Sharks have ample opportunities to feed.

  • Once the spawning season is over and water temperatures, and consequently, the Sharks' metabolic requirements increase, the Reefies gradually disperse again, and residency at Tetamanu decreases as even the highly resident individuals are forced to sometimes roam in search of prey.
My takeaway?
  • There is no inverted trophic pyramid in Fakarava Atoll.
    Yes in the passes there are local Shark aggregations and because of that, the trophic pyramid is locally skewed -  but just like in the case of Sala's remote islands, there are external subsidies and the Sharks also roam, meaning that the relevant area one has to consider is far, far larger than the mere area of the passes. And over that whole area that comprises the lagoons but also the outer slopes, the pyramid is clearly normal as the biomass of Sharks is orders of magnitude smaller than that of lower trophic levels.
    Incidentally, that's not that dissimilar from our feed on Shark Reef where the astounding temporary predator biomass is in no way representative for the trophic pyramid of Beqa Lagoon let alone the whole of Fiji!

  • For me, these latest findings mean that until somebody comes up with solid evidence in line with the data collected by Johann et al, I will continue to call BS on Sala's hypothesis of there being inverted trophic pyramids on pristine reefs!
Enjoy Johann's paper!

Thursday, July 28, 2016

Why do Hammerheads swim on their Side?


But first, watch this video at 1:23ff.

Those are Scalloped Hammers off Mozambique.
See how several individuals are swimming on their side? Seen it a squillion times in the Galapagos, Malpelo and Cocos and always thought they were doing it in order to better watch me.

Possibly - but possibly not!
Have a look at this astounding paper about GHH!
Turns out that for those Hammerheads with large cephalofoils and large dorsal fins, swimming on the side helps conserve energy. It looks like the development of extended hammers for better predation and large dorsal fins for better maneuverability/tighter turns did come at an energetic cost which is being (partially?) offset by the rolling swim pattern - e.g. see this video of a GHH.
Or as one of the authors writes,
My theory is: Hammers are about 5 million years old – young for sharks, and the winghead and great hammer are the oldest species of the hammers, and they also have the biggest heads. The younger species have much more reduced heads, so Im guessing that hammers as a group first developed this big ole head, which is great for hunting, and a big dorsal to also help with maneuvering while hunting – but then realised that this head is actually pretty shit for cruising about (not efficient). Hey, but when I swim on my side that works much better.

Then as the newer species evolved, the head is reduced – a tradeoff between the hunting benefits and transport. 
Like I said, simply awesome! 
Kudos to the authors for a) observing the behavior, b) developing the hypothesis and c) providing for compelling evidence, even going as far as to build a model and test it a wind tunnel. This is exactly how good science should happen!

Well done folks - very impressive!

Sunday, July 24, 2016

Shark Dive Tourism: The Good, The Bad and the Future!

If you're at DEMA 2016, you really must attend.
The speaker is of course none other than my irreducible friend Rick, and the topic will undoubtedly be his Sustainable Shark Diving project, hopefully with some first insights about operators, client preferences and public acceptance.

Regarding the latter.
I'm frankly disappointed but upon reflection, I'm really not that surprised. Essentially, my conclusion is that most of our clients are mere consumers: they purchase the product, enjoy the experience but don't really want to be bothered with deeper thoughts about ecotourism and sustainability.

Take our case.
We're doing OK, thank you - but that's merely the result of an initial flurry of enthusiasm, and the reviews have since been few and far between.
Yes our research and our conservation achievements are impressive, yes our customers very much enjoy Ben and Manoa's education and awareness presentations, yes everybody is happy to make a contribution to the villages, yes we regularly win awards and are generally considered to be one of the best of class in Shark ecotourism, yes we host and interact with a myriad of committed Shark people, be it professional conservationists, researchers, professional media people, selected activists, scholars, students or volunteers - but those are not our typical tourist Shark divers. 
Due to the nature of the animals we showcase but also, owing to the way we have chosen to conduct matters, our Shark dive is essentially a tightly choreographed show that aims to be a safe and sustainable tourism product rather than some sort of a personal experience. And consequently, we aren't really compatible with either the troglodyte adrenaline junkies or the Shark huggers, let alone the self-promoting media whores; and the dreaded semiprofessional image hunters with their fisheye lenses have learned to frequent more accommodating operators.

Instead, our typical customer is your quintessential traveling Joe diver. 
They are first and foremost tourists, will do a Shark dive among many other things, are generally not terribly experienced or committed, generally visit for merely a day or two, want to experience guaranteed Shark encounters, want to be served, want to feel safe, want to take a few snaps and want to purchase a memento of their experience. Generally, they love our product and will love us on TripAdvisor - but that's that, the more as Fiji will offer them plenty more fabulous tourism activities and wonderful people to experience and tell about.

And the others?
Many of the really good operators are probably too successful and too busy to bother promoting SSD; and the bad ones are obviously not interested in undergoing an objective review. 
And when it comes to the other diving Shark enthusiasts, they too often have agendas (as in experiencing extreme encounters or taking extreme pictures) that may well conflict with the kind of tourism SSD is trying to promote.

But I'm obviously speculating as usual.
Rick may know more and it will be really interesting having him share his insights - plus he's a great orator and simply a great guy.
In brief, highly recommended!

See you in Las Vegas!

Thursday, July 21, 2016

Are Bull Sharks particularly aggressive?

Of course not!

In fact, rather the opposite!
Contrary to much more assertive species like e.g. Silvertips, Galapagos' and Grey Reefies that have no qualms approaching, and sometimes even harassing SCUBA divers, Bulls are much more wary and appear to actively avoid us, to the point that they will generally only approach people underwater when attracted by food. I call them shy bodybuilders - but bodybuilders they are, large and immensely strong, and they definitely demand to be always treated with great circumspection and respect!

And the numerous bites?
Like our newly minted sharxpert (my oh my! :) ) Lindsay explains, Bull Shark habitat coincides with the areas most frequented by people, meaning that the chances for encounters are comparatively larger - and then, everything goes, from mostly nothing to mistakes to agonism (= aggression) all the way to outright predation = not aggression! 
But yes - forget the legends about the exceptional aggression, the testosterone and the high territoriality that are nothing but unsupported BS!

Anyway, just saying!
I was away and have only now seen Lindsay's interview, and wanted to state that I very much agree. Nothing beats personal experience - and that she certainly got!

Attagirl - well said!

Wednesday, July 20, 2016

Epic Diving join Global Shark Diving!

Epic - literally!
When it comes to Bahamian Shark diving, Debra and Vincent may be the new kids on the block - but contrary to others who continue to regale us with fake Shark conservation media featuring the latest batch of pink-clad bimbettes, the Canabals don't talk from both sides of the mouth but have instead pursued a strategy of combining solid ecotourism with Shark conservation, research and education from the get go. What I particularly like is how they've managed to completely turn around the image of the once much reviled Oceanic Whitetip, a highly assertive species that was widely thought to be completely unsuitable for tourism, let alone for diving without cages - and yes on that point, yours truly stands totally corrected!
So very well done, and welcome to the team!

And now we are ten.
I can say with absolute certainty that when it comes to Shark ecotourism, these operators are truly the best of the best - meaning that finding new candidates that fulfill all of our guiding principles is becoming increasingly challenging, the more as each of our members and ambassadors can unilaterally veto any proposal. Personally, I'd like to see the next member hailing from the Indopacific, ideally Asia - but it ain't gonna be easy!

Check out the above principles and if you know of anybody, tell us here!

To be continued!