Re: Bubble nets question

From: Phil Clapham (phillip.clapham@noaa.gov)
Date: Tue Oct 09 2001 - 15:49:48 EDT


Hi Chris:

Great question! We're not entirely sure, but it seems that two things
happen with bubble nets (and bubble clouds, which are huge bursts of
bubbles with no open space inside the edges; clouds are different from
nets and they are much more common in the North Atlantic humpback whale
population). First, the bubbles are indeed a barrier that the fish
can't get through - they're a lot of air, and that's very difficult for
small fish to swim through. But it's also likely that they scare the
fish and make them bunch together more tightly. This is what fish do
when they're threatened by something that wants to eat them (what we
call their "predators"). It's a very good thing to do for most their
predators because they're mostly trying to catch individual, single fish
and bunching up makes it more difficult for predators to do that. BUT,
it's a lousy reaction to a whale because the whale wants to eat the
whole fish school, and bunching up just makes it much easier for the
whale to do that!

Phil Clapham

Holly wrote:
>
> Dear Scientist,
>
> Why don't fish just go through the bubble nets when whales make
> them? Do the bubbles stun them, or are they just scared? Or have they
> already tested that if you try to swim through the bubbles, you will get
> stuck. We saw about the bubble nets in a movie at the planetarium, and
> I was wondering. My name is Chris and I am 7 years old. Please tell me
> soon.
>
> Thank you.
>
> Chris Rockwell

-- 
The Society for Marine Mammalogy will be holding its 14th Biennial
Conference from 28 November to 3 December 2001, in Vancouver, BC.  Visit
the conference Web site at www.smmconference.org for full details of
this important meeting.

Phillip J. Clapham, Ph.D. Large Whale Biology Program Protected Species Branch Northeast Fisheries Science Center 166 Water Street Woods Hole, MA 02543, U.S.A.

tel. 508 495-2316 fax 508 495-2066 email: phillip.clapham@noaa.gov



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