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And there's Western Australia's world-leading method
for predicting and managing rock lobster populations - a shining
example of cooperation between scientists, managers and fishers.
These are among the many insights into the mysterious
life of nature's most delectable crustacean, the lobster, in a new
book from CSIRO Publishing. Lobster Biology and Management is
a special issue of the journal of Marine & Freshwater Research,
containing the proceedings of the 6th International
Conference on lobster biology and management.
The lobster mass-suicides were reported by a South
African scientist, Dr Andrew Cockroft. Five have been observed in
recent years, involving the stranding of an estimated total of 2263
tonnes of lobsters!
They were triggered by 'red tides' - massive blooms
of toxic dinoflagellates - which deplete the oxygen in the deeper
waters, forcing the desperate crustaceans into a 'last gasp'
migration into the shallows where they are stranded by the tide.
Anxious researchers rescued several tonnes of lobsters and trucked
them along the coast to an unaffected area where they were released
back into the sea.
The 'trap that wasn't' was discovered by US
scientists studying the behaviour of lobsters in traps, using a
video camera.
It turned out the lobsters were a lot smarter than
the people who designed the traps - only 6 per cent of those that
entered were actually caught, while 94 per cent got away. And those
that actually entered the trap were only 4 per cent of all the
lobsters that approached it!
The trap used was the US Government's
officially-approved lobster catching device, underlining the fact
that officialdom doesn't know a lot about lobster behaviour.
Furthermore, of the escaping lobsters, 72 per cent exited by the
'front door' - which they should not have been able to do.
One of the world's most-admired systems for modelling
and sustainably managing a fishery, that developed for the WA rock
lobster industry, is soon to be trialled on the $90M/year Southern
Australian rock lobster fishery, says CSIRO marine researcher Dr
David Griffin.
The method depends on studying ocean currents and
winds to forecast the number of baby lobsters that will be swept in
from the open sea to settle on the coast. Changes in these
conditions can cause settlement by larval lobsters to fluctuate as
much as fivefold.
In WA a clear correlation between natural conditions
and lobster settlement has been defined, and researchers are hopeful
that similar rules may apply to east- and south-coast lobsters -
though at the moment, the determining conditions are a complete
mystery, says Dr Griffin.
"We believe that variations in lobster settlement are
best explained by changes in conditions in the ocean, rather than
along the coast. These variations in settlement strongly determine
the catch a few years later, causing it to vary as much as 100 per
cent from year to year and making it difficult for fishermen and
managers.
"We need to understand the governing factors if we
are to ensure the fishery is sustainably managed. At the moment it's
a completely open question - there isn't even a decent hypothesis,"
Dr Griffin says.
Australian fisheries and marine scientists
contributed 20 per cent of the papers to Lobster Biology and
Management, the second largest contribution by any country after
the US.
The special issue of Marine & Freshwater Research,
Lobster Biology and Management, is available from CSIRO
Publishing for $95.
More
information:
Dr
David Griffin, CSIRO Marine Research 03 6232 5244
Ann
Grant, CSIRO Publishing 03 9662 7618
Email:
ann.grant@csiro.au
www.publish.csiro.au
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