Sunday, June 21, 2009

Not hard to stomach!

Well worth clicking on! Bravo Lill!

Juerg is cranking them out as always.
This time, it's a methodological paper about our acoustic telemetry data collection.

As you may remember, any research within Shark Reef Marine Reserve has to fulfill two preconditions:
- Is it contributing directly to Conservation?
- Is the method employed the least invasive possible?

There are several methods for deploying acoustic tags and many of them involve catching the animals, after which the tags get attached via a loop around the caudal peduncle, or via tie wraps through a hole drilled into the dorsal fin or even implanted via a small subcutaneous incision.
Here's an example with satellite tags - not for us!

We don't do any of that as we try to avoid any undue stress to the animals and also, because we don't want to "punish" them for having trusted us.
Until very recently, we have resorted exclusively to hand feeding our tags after having hidden them in fish heads or wrapped them into strips of fish loin. It's quite funny as the Sharks do clearly detect the tags' pinging and have to be "conned" into swallowing the bait by quickly switching the pieces once they are committed to taking them. This method is quite wasteful as the tags get excreted (often via stomach eversion) and thus lost after a relatively short time.

Last September, we started to attach some tags externally by using pole spears or spearguns.
The Sharks don't seem to mind much and have all come back - and still, every time, I cringe when I see happen. The reason why I have OKd it is that we want to track the animals during their mating season when they generally refuse to feed. As a added advantage, Juerg is now getting some very useful long-term data as the tags will stay on for several months.

Juerg's paper is titled Tracking free-ranging sharks with hand-fed intra-gastric acoustic transmitters and deals with the abovementioned hand-feeding technique. You can read an excerpt on his blog or purchase and download the whole paper right here.

More papers very shortly indeed!


Wilson said...

Reminds me of trying to feed the dog his worm tablets by hiding it in the food. They know you're trying to feed something that they're not quite happy with, and resort to alot of hemming and hawwing before anything gets swallowed. I guess with sharks it would be a lot harder, since you can't exactly smile and look convincing :P

DaShark said...

You obviously don't know Rusi!

OF COURSE he begs and cajoles - exactly like you would do with Fido!
We all smile when we hear him but hey, it sure works!

His most recent experiments consist in trying to direct the Sharks with hand signals, much like a traffic cop - again, very funny!
It's still very much in its infancy, but Sharks are very good learners and I wudn't be surprised if that, too, would work in the end.

Wilson said...

I predict a future where traffic policemen must past the ultimate test before graduating as a proper traffic policemen: directing shark traffic ^_^ Failure is definitely not an option ><

DaShark said...

Can't be deadlier than the fitness tests implemented by the last Police Commander - remember? (:

Tafa said...

haha... i remember that.

Lui has managed to teach some fish hand traffic signals, he was practising while we were down there. Was really amazing to see fish responding to his hand movements