DEPARTMENT OF FISHERIES ANNUAL REPORT TO THE ...

AgENCy PERFORMANCE � CASE STUDy 2
Hi-tech tagging helps manage Cockburn
Sound snapper stocks
Department of Fisheries research carried out in
Cockburn Sound during 2010/11 has used high
technology acoustic tags to track the movements of
pink snapper to and from the area. Cockburn Sound
is the only significant spawning area for pink snapper
in the West Coast Bioregion – the stretch of coast
running from east of Augusta to the Zuytdorp Cliffs,
north of Kalbarri.
Every year, some time between August
and December, thousands of adult pink snapper
congregate in Cockburn Sound to release their eggs
and sperm, as part of what are known as ‘spawning
aggregations’. As a result, there is an annual seasonal
Fisheries researcher with a pink snapper (Inset: pink snapper
with tags near dorsal fin).
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closure to pink snapper fishing in the area (extended
as part of a package of management changes in
2005), which runs from October 1 to December 15 to
protect these spawning fish.
Fish that join the spawning aggregation in
Cockburn Sound reach sexual maturity when they
are about six years old and 600 mm in length.
These fish are much larger relative to those from
other areas in the West Coast Bioregion – which
means they can produce relatively larger numbers of
eggs – and are thus very important for pink snapper
stocks in the entire bioregion.
The Department of Fisheries has been
conducting surveys since 2001 to estimate
the spawning biomass of snapper that form
the aggregations in Cockburn Sound each year.
Preliminary estimates suggest the biomass was
declining prior to the management changes in 2005,
but has subsequently increased as the result of
factors such as changing the timing and extending
the length of the closure from six to ten weeks, and
adjusting the daily bag limit so that a maximum of
one fish over 70 cm in length could be taken.
Other factors that have helped to increase
the spawning biomass include an influx of mature
pink snapper into the Cockburn Sound spawning
population from the strong stock recruitment that
occurred in 1999.