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Sperm whales (Physeter macrocephalus) interaction with long line


Stephen Cotterell <[log in to unmask]>


Scientific forum on fish and fisheries <[log in to unmask]>


Wed, 21 Feb 2001 14:46:56 GMT





text/plain (1 lines)

Greeting Fish-Sciers, Fish-ecologyers, and Marine Biology Forum subscribers

This morning I've had an interseting conversation with a Canadian fisherman
regarding a potentially very serious bycatch problem.

He's a longliner working out of a British Columbia port, and fishes quite deep,
around 300 ftm I seem to remember. His problem is that when he hauls his gear
he finds its been striped by sperm whales. He certain it is sperm whales
because he's seen them when hauling and indeed he's had one entangled in his
back line, which subsequently died.

I am certianly no expert on this, but he has heard of some acoustic work going
on in this lab and approached me in the first instance.

I beleive he's looking for an acoustic device to keep away the sperm whales
when hauling. He reported no problem when shooting his gear so it seem likely
that its the struggling of the lip caught fish which is attracting the whales,
though we didn't discuss which species of fish he's catching, he said after a
six hour set they are still very much alive. The depth may mean that this
sound is propogated a great distrance. I cannot remember exactly how deep is
the sofar layer. Also, the boat's echosounder may play a part in attracting
the whales to the area but he said this is running all the time. I'm aware
that sperm whales use echolocation to find prey so perhaps a generated signal
which interferes with this on a local scale may be useful. I also suggested he
turnes off his echosounder when hauling may be useful, though even the noise of
the hauler pulling up the line could attract the whales. Does anyone know?

I'd imagine that sperm whales use quite low frequency sounds to communicate but
perhaps higher frequency sounds to echlocate as they get closer to their prey.
I wouldn't imagine that sperm whales are messy eaters and also that they exist
soley on a diet of giant squid. Does anyone know what is the frequency range
of sperm whales? Which sounds accompany different bahaviours? And has anyone
tried blocking sperm whale's echolocation?

Maybe there is another apporach intirely. I'm aware of the electrical shark
repellent systems used by divers. It might be possible to discharge a current
through the fishing gear to deter the whales, but I'd imagine the sensory
systems of sharks and whales to be very different and the practicalities of
discharginging sufficient current might leave little room on a fishing vessel
for the catch and put in jeopardy the lives of the crew!

This is a serious request for information. I said I'd pass on any thoughts
generated by this message. Please feel free to discuss this but it is probably
best if you contact me directly. I'll post a full set of contributions if and
when I get something.

With thanks


-Stephen Cotterell
-Fishery Science Lab
-Rm 4 22 Portland Square
-Institute of Marine Studies
-University of Plymouth
-Drake Circus
-PL4 8AA
-Tel +44 (0)1752 232411
-Fax +44 (0)1752 232406
-e-mail [log in to unmask]

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