Friday, July 17, 2009


Different Ocean, same controversy - and same perpetrators!

The opponents of Hawaii's "Shark dives" (they're actually totally harmless and educative snorkeling tours) try to make the case that baiting for Sharks three miles offshore may induce the Sharks to follow the boats back to shore where they then pose a hazard to the beach goers and aquatic recreationists.

Absolute Humbug!, says this study by Meyer and others of the UH Mānoa Hawai'i Institute of Marine Biology:

The public safety implications of shark cage diving operations are arguably the most contentious aspect of these activities.
A recent study of the white shark cage diving industry in South Africa concluded that specific conditioning associated with these activities makes them unlikely to increase the risk of shark attacks on recreational ocean users in adjacent areas (Johnson & Kock 2006).
This is despite the fact that white sharks are the species most frequently implicated in shark attacks on people (430 attacks worldwide; G. Burgess, International Shark Attack File, personal communication 2007).

Our study indicates that current Hawaii shark diving operations also pose little risk to public safety.
The shark assemblage associated with these activities was numerically dominated (> 98%) by Galapagos and sandbar sharks, which rarely bite people. Worldwide, there have only been five confirmed unprovoked attacks attributed to sandbar sharks and only one attack attributed to a Galapagos shark (G. Burgess, International Shark Attack File, personal communication 2009). Other potentially dangerous species (tiger shark, hammerhead spp. or white shark), occasionally visit Hawaii shark cage diving sites, but there is no evidence that the rate of shark attacks along the adjacent coast has increased significantly since the advent of shark cage diving operations in 2001. There were five confirmed shark attacks along the north coast of Oahu (38 km stretch of coastline between Kaena Point and Kahuku Point) during the 1990s (Global Shark Attack File [GSAF] 2009) and five confirmed shark bites in this area between 2000 and 2008 (GSAF 2009, Hawaii Division of Aquatic Resources 2009).

Negligible impact on public safety is also supported by:
(1) the remoteness of the sites,
(2) the fact that the shark tours mimic activities of crab fishing vessels which have been operating in the same area for over 40 years and
(3) inshore recreational stimuli (such as a surfer paddling on a 3msurfboard) substantially differ from the conditioning stimuli associated with tour operations (c. 10 m diesel powered vessels operating several km offshore), and hence are unlikely to stimulate a conditioned feeding response (Johnson & Kock 2006).

Seriously, does anybody really think this is anything but good, safe and harmless fun?

Incidentally, I was just sent the following by "somebody" very prominent who lives in Hawaii and is intimately acquainted with local circumstances. I can categorically state that he's generally as pragmatic, impartial and well reasoned as they come and not at all an exponent of the tree-hugging activist faction of Shark Conservation.

Did you catch Jim Rizzuto's column in West Hawaii Today on Monday?
It seems that a charter sportfishing boat was on its way into Honokohau Harbor and decided to try for some fun near the harbor entrance. They hooked up a Whitetip, which was then bitten in half by a Tiger Shark. When a fisherman feeds a Shark (even one that belongs to a species that has declined drastically in population over the last decade) to another Shark, it's GOOD FUN!
If you go out to look at a Shark to appreciate it and learn about it, it's a statewide threat.

A diver was circled by two Tiger Sharks for 20 minutes recently at the entrance to Honokohau Harbor.
Every knows why the Sharks are there: because the sportfishing boats dump their carcasses there on their way back into the harbor (or in many cases, dump the carcasses in the harbor, with the smell and sometimes the carcasses themselves going back out with the tide). When fishermen pollute the harbor and attract the only dangerous species of Shark we have here into an area that is one of the island's most popular spots for snorkeling, diving, and surfing, and home to endangered Sea Turtles, Dolphins, and (seasonally) Humpback Whales with calves, it's NO PROBLEM.

If divers maintain a population of small Sharks, never implicated in attacks on humans here, at a location over 3 miles offshore and far from any other recreational water activities, it's a CRISIS! Of course, when that same population of Sharks was being maintained in that same area by fishermen it was NO PROBLEM.
Hmm - must be a simple rule in here somewhere that could explain this logic....



Dr. Simon Pierce said...

Excellent points! It's very easy for people to focus on the more 'visible' shark/human interactions like cage diving, while disregarding more insidious practices like fish-dumping.

Another paper examined the impacts of white shark cage diving in South Africa (Laroche et al. 2007. Marine Ecology Progress Series). From their abstract:

"Although ecotourism activity had an effect on the behaviour of some sharks, this was relatively minor, and the majority of sharks showed little interest in the food rewards on offer... consequently, moderate levels of ecotourism probably have only a minor impact on the behaviour of white sharks, and are therefore unlikely to create behavioural effects at the ecosystem level."

A caveat is that these two studies are both referring mostly to 'pelagics' rather than more site-attached species like reef sharks. Great column though, this is an important debate - particularly for places where the choices basically boil down to either (1) create an economic value for 'live' sharks, or (2) suffer major population declines from fisheries.

Good work!

DaShark said...

Thanks Simon.

I'm frankly amazed when people claim that cage diving may lead Sharks to "associate humans with food".
And that's not even what they mean: what they mean is "REGARD humans AS food", which is even more far-fetched.

Sharks have very limited cognitive faculties, if any at all.
Common sense dictates that they will

- aggregate where food is being regularly offered. Apparently, the sites in Hawaii were chosen because the Sharks were there already - in response to stimuli created by the crab fishermen

- maybe, learn to associate the noise of boats with the chance of a meal

But to then jump to the conclusion that those Sharks look beyond the boats and the cages and "understand" the much less immediate correlation with the people in them is really pushing it way too far.
To then postulate that because of those "insights", Sharks will start devouring people on the beach is quite frankly ludicrous.

We feed Sharks (among them the much maligned Bulls and Tigers) and to us and anybody else engaging in that activity, it's blatantly obvious that the animals are only interested in the food we give them. It's equally obvious that they just do not, ever, regard us as a potential meal.

The "association" hypotheses are just idle, although intuitively, somewhat plausible speculation. Whenever put to the test, they have always been rejected as false.