INSTITUTE FOR MARINE AND ANTARCTIC STUDIES
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Transcript of INSTITUTE FOR MARINE AND ANTARCTIC STUDIES
INSTITUTE FOR MARINE AND ANTARCTIC STUDIES2012 May/June BSCZSF Surveys
www.imas.utas.edu.au
IMAS - in collaboration with the Tasmanian State Government
• 234* sample tows conducted by 2 vessels in the BSCZSF in May/June 2012. • Three main areas: 1 (Western Protected Area), 2 (2009 open area and viable area 10), 3 (Southern Protected Area), Area 4, Area 5* (not shown) and Area 6 (Lady Miriam – Edge of 2011 Area)
Area 1 (Western Protected Area):
• 48 shots (NS only)• Average density 14 kg/1000 m2
• Ave New dead shell per shot 6%
Nov 2011 2012Area (km2) 123 147Upper 95% CI (t) 2707 6880Mean (t) 2247 5887Lower 95% CI (t) 1787 4894
Biomass Estimate (33% efficiency)
Area 1 (Western Protected Area)
Size Frequency (2385 scallops NS only)
November 2011 Size Frequency (965 scallops)
Area 2 (2009 Open Area and Viable Area 10):
• 40 shots (Anne B only)• Average density 10 kg/1000 m2
• Ave new dead shell per shot 16%
Biomass Estimate (33% efficiency)
Nov 2011 2012Area (km2) 102 61Upper 95% CI (t) 3985 2425Mean (t) 3068 1868Lower 95% CI (t) 2150 1312
Size Frequency (1463 scallops AB only)
November 2011 Size Frequency (1053 scallops)
Area 3 (Southern Protected Area):
• 48 shots• Average density 9 kg/1000 m2
• Ave New dead shell per shot 23%
Biomass Estimate (33% efficiency)
July 2011 Nov 2011 2012Area (km2) 140 43 92Upper 95% CI (t) 2700 4922 3172Mean (t) 1880 4043 2368Lower 95% CI (t) 1060 3164 1564
Size Frequency (761 scallops)
November 2011 Size Frequency (694 scallops)
Area 4: Size Frequency (386 scallops)
• Average density
5 kg/1000 m2
Area 4: November 2011 Size Frequency (137 scallops)
• Average density 5.4 kg/1000 m2
Summary• Only Area 4 was below the discard rate, but had
low densities.
• Area 1 scallops ranged from 69 to 123 mm and the discard rate was 25.1%. A large number of the undersized scallops were in the 80-89 mm size classes.
• Area 1 had an average scallop density of 14 kg per 1000m2. This equates to approximately 0.15 scallops per m2 of the benthos.
• Area 3 appears to have declined since November 2011.