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.