Thursday, July 17, 2014

A Revolution in Shark Control?

Shark cull in Reunion - source.

Have you seen this?

I must say that I'm irritated - intellectually that is.
So, the cull in Hawaii did not reduce the incidence of shark bites. Indeed, because those are highly migratory Tiger Sharks, and new Sharks moved in and took the place of those individuals that were removed by culling - correct?

The target species of the WA Shark cull are those highly migratory GWS.
So if lethal removing of migratory Sharks has been shown not to work in Hawaii - what leads us to boldly state that non-lethal removing of migratory Sharks in Western Australia will?
Can't have it both ways!

And why did the relocating work in Recife?
Because those were Bull Sharks = a not highly migratory species! The Sharks were dragged offshore and released, after which they likely settled somewhere else on the coast and/or may have learned to avoid the region were they had been subjected to such a traumatic experience.

Which begs the question, would this strategy work in Reunion?
Alas, methinks not - because the island is so small that it likely does not feature any "unproblematic" coastlines for the Sharks to relocate to, and because it is too isolated for the Sharks to swim somewhere else! By the same token, in Reunion, culling is likely to reduce the incidence of Shark strikes as it will gradually whittle down a discrete resident population of Sharks.
Not nice - but people are working on alternative solutions!

The good news?
The data from Western Australia's Shark Bay are much more ambiguous, meaning that a good portion of those WA Tiger Sharks are likely not highly migratory - remember this post? Tiger Shark migration appears to be mediated by the geographical location insofar as closer to the equator, temperatures vary less, prey migrates less and thus evolution has not selected for Tiger Sharks to go walkabout.
And if so, relocating those WA Tiger Sharks may well work!

Detail detail!
Or am I missing something here?

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