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NEFSC/Industry Cooperative Survey Gear Study 28 October – 6 November, 2002 PowerPoint PPT Presentation


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NEFSC/Industry Cooperative Survey Gear Study 28 October – 6 November, 2002. OBJECTIVE.

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NEFSC/Industry Cooperative Survey Gear Study 28 October – 6 November, 2002

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NEFSC/Industry Cooperative Survey Gear Study

28 October – 6 November, 2002

OBJECTIVE

To examine differences in catch rates of the R/V Albatross IV using standard Yankee #36 trawls in two configurations; one configuration that conformed to standard specifications and a second configuration that was known not to meet specifications, including offset trawl warps.

Source Document: Specifications for Construction of NEFSC Standard #36 Bottom Trawl


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SAMPLING AREAS

  • General sampling areas provided by industry

  • Specific areas determined onboard the ship

    shallow - approximately 87 m (47.5 fm) in depth

    mid-depth - approximately 139 m (76 fm)

    deep - approximately 198 m (108 fm)

  • Areas selected in order to cover a range of depths and to sample

  • as many species as possible

  • Original plan was to sample 2 areas in 1 depth zone then 2 areas

    in a second depth zone

  • Weather prevented occupation of 4 areas; therefore a third

    ‘shallow’ area was sampled


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Area 2

100m

Area 1

Area 3

NEFSC/Industry Cooperative

Survey Gear Study – Part I

28 October – 6 November, 2002

Location of Sampling Areas

Closed Area I


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BOTTOM PHOTO from NW CAI (Area 1)

Albatross Cruise 99-08, July 1998, Site I2

Image provided by Page Valentine, USGS, Woods Hole Field Center


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BOTTOM PHOTO from NE CAI (Area 2)

Albatross Cruise 99-08, July 1998, Site I2

Image provided by Page Valentine, USGS, Woods Hole Field Center


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STATION SELECTION

  • The areas were 5-minutes by 5-minutes (approximately 25 nm2)

  • Each area was subdivided into 25 blocks, each 1-minute by 1-minute

  • Each block was further subdivided into four quadrants

  • Sixteen blocks were chosen, the maximum possible number of

  • stations that could be performed during one 24 hour period,

  • using uniformly distributed random numbers

  • Stations were then placed in a randomly selected quadrant within

  • each block


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4.75

4.25

3.75

3.25

2.75

2.25

1.75

1.25

0.75

0.25

GRID USED TO POSITION TOW STARTING POINTS


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TOWING PROTOCOLS

  • Each area sampled for 48 hours

  • Order of gear configurations used determined by coin toss

  • One randomly chosen gear configuration was used for 24 hours,

  • then configurations switched and tows made at the same locations

  • the following day

  • Tows offset by approximately 1 additional hour to account for tide

  • and light conditions

  • Direction of tows determined by the Captain of the F/V Sea Breeze

  • Constant scope used for all tows within an area. Scope chosen

  • was that used for the deepest likely depth in an area


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SCOPE AND TRAWL WARP OFFSETS USED IN EACH SAMPLING AREA


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GEAR SPECIFICATIONS - R/V Albatross

‘Optimal’ (OPT)

  • Net #21, constructed prior to the experiment and inspected to meet

  • the specifications by industry representatives

  • Doors used (Pair #38) were inspected by industry representatives

  • to meet tuned door specifications

  • Backstraps used were fitted with swivels (with the appropriate

  • number of links removed to maintain standard specification) to

  • ensure that there were no twists in the chain while the net was

  • fishing

  • Even trawl warps; re-measured and certified the day of sailing


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GEAR SPECIFICATIONS - R/V Albatross

‘Worst Case Scenario’ (WCS)

  • Net #14, used during the 24-27 October, 2002 ‘video cruise’

  • (the last 4 days of Leg II of AL 02-09, Autumn Bottom Trawl

  • Survey)

  • Pair #37 doors considered to be performing poorly during the

  • ‘video cruise’

  • Backstraps with no swivels and intentionally twisted 2 times

  • Trawl warps offset to match the mis-marked warps used during

  • 2001-2002 surveys


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GEAR SPECIFICATIONS - F/V Sea Breeze

  • Standard 6" mesh groundfish net

  • 16” (with 12” at wings) rockhopper footrope with 2” cookies

  • 110' sweep

  • 30 fm groundcable used in Area 1

  • 50 fm groundcable used in Areas 2 and 3

  • 2.4” (6 cm) mesh codend liner


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GEAR SPECIFICATIONS


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 1: NW Closed Area I

‘Optimal’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 1: NW Closed Area I

‘Worst Case Scenario’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 1: NW Closed Area I

29-30 October, 2002


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 2: East of Cape Cod

‘Optimal’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 2: East of Cape Cod

‘Worst Case Scenario’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 2: NW Closed Area I

31 October-3 November, 2002


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 3: NE Closed Area I

‘Optimal’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 3; NE Closed Area I

‘Worst Case Scenario’ Configuration


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Albatross IV Tows

Sea Breeze Tows

Location of Paired Tows

Area 3: NW Closed Area I

3-5 November, 2002


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SAMPLING PROTOCOLS

  • Albatross

  • Catch sorted by species and weighed (nearest 0.001 kg) using

  • motion compensated digital scales

  • Lengths of all fish measured (nearest cm)

  • All catch and biological data were recorded using the shipboard

  • automated data entry system

  • Sea Breeze

  • Catch sorted by species and weighed using same scales

  • Individual fish lengths were taken on a subsample of the catch

  • when time allowed

  • Catch weights were recorded on standard fisheries observer program

  • logsheets and transmitted to the Albatross

  • Catch numbers and individual fish length data were also recorded on

  • fisheries observer program logsheets and processed at the Woods

  • Hole Laboratory the day after the cruise ended


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SUMMARY OF TOWS CONDUCTED

IN EACH SAMPLING AREA


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