Monday, June 14, 2010

Does Shark Feeding influence Shark Behavior?

Another fabulous pic from Sasha's 2010 crop!

From my sneak copy of the program of Sharks International.

Tropho-spatial consequences of tourism-related shark feeding: impacts on reef sharks and sympatric fish communities
Maljković, Aa & Côté, IMa
aSimon Fraser University, BC, Canada (amaljkov@sfu.ca; imcote@sfu.ca)

Shark feeding, as a tourist attraction, is seen as either an economic incentive to conserve sharks, or an activity detrimental
to shark behaviour and human safety.
Despite the debate surrounding shark feeding, and the popularity of shark diving,
few studies have examined the impact of shark feeding on the species provisioned, or on sympatric fauna.

We used a
combination of direct observations, acoustic telemetry and stable isotope analysis to measure the impact of provisioning on the behaviour and trophic signatures of a population of Caribbean reef sharks (Carcharhinus perezi) in the Bahamas.
In addition, we conducted visual surveys of reef fishes at various distances from a shark feeding site to elucidate the
eff ect of shark provisioning on reef-fish assemblages.

Of the sharks that regularly attended feeding events, only a few
of the largest ones were successful at acquiring bait.
Bait consumption was reflected in the 15N isotope content of the
muscle tissues of these sharks, but it had little effect on ranging behaviour. Fed sharks exhibited residency times at the feeding site and daily travel distances that were similar to those of unfed sharks in two control groups.

Reef fishes at
the shark feeding site were more abundant and diverse than at adjacent sites, and the abundance of species targeted by fishers decreased with increasing distance from the feeding area.

Shark feeding therefore appears to have little
impact on shark behaviour but shark aggregations at feeding sites may influence reef fish communities, perhaps through competition between sharks and fishers.

Bloody awesome - and pretty much what we in the Industry have been saying all along!
More as I get my hands on the paper.

4 comments:

BeachNomad said...

Good information, details on larger sharks such as the bulls here in Fiji would surely follow the trend as some fish heads every other day or so can not sustain the large numbers that appear on the dives. They are obviously going off and doing their own thing and returning for a nice morning snack when it suits them.

Love to get the paper when you get your hands on it!

DaShark said...

Yup that's exactly what our data tell us: individual Sharks will come, maybe stay 1-2 days and then wander off, only to re-appear days or even weeks later.

Plus, not all of them feed and those who do, not every time.

It's a big Ocean out there & I have no doubt that they generally continue pursuing their Sharky lives, as it should be.

Ans Vercammen said...

I am not too convinced, as there is plenty of evidence from the scientific community that shark behaviour is negatively affected by provisioning. For instance: http://biol09.biol.umontreal.ca/numecol/Reprints/2010_Clua_et_al_MEPS_2010.pdf
New observations from the Philippines on whale shark feeding in Oslob demonstrate significant changes in whale shark movements: they stayed on the surface for extended periods of time, which is very unusual. Sharks are generally crepuscular feeders, so providing food during the day is in itself changing their eating patterns.
Suffice it to say that shark feeding remains highly controversial, and has been banned in several areas.

DaShark said...

Yes you are correct, there are certainly local effects.

It's a highly nuanced topic and I invite you to properly document yourself before jumping to conclusions.
E.g. the example from Moorea is valid, the one from Oslob not so much.

If you care, you can find plenty of resources here.