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7 January 2010


CRUISE RESULTS


NOAA Fisheries Research Vessel DELAWARE II Cruise DE 09-10 (Parts 1 - 3)

Atlantic Herring Acoustic Survey


CRUISE PERIOD AND AREA


Cruise operations were conducted on the continental shelf (depths to 350 m) in the Gulf of Maine and northern Georges Bank regions, including the Canadian Exclusive Economic Zone on eastern Georges Bank. The 2009 Fall Atlantic Herring Acoustic Survey was conducted during three parts between 12 September and 15 October 2009 (Figures 1-3). Part 1 of the survey (12-17 September) was dedicated to calibrating the scientific echo sounders on the FSV Delaware II, collecting acoustic and optical data with the Advanced Fisheries Tow Vehicle (AFTV), and conducting an abbreviated survey of Atlantic herring in the Georges Bank region. The annual systematic acoustic and biological survey of Atlantic herring was conducted in the Georges Bank region during Part 2 (21 September to 2 October) and into Part 3. Part 3 of the cruise (6-15 October) was dedicated to completing the herring survey, a fine-scale acoustic survey and experimental acoustic and optical measurements in the Georges Bank region as well as a systematic survey of Atlantic herring in the Jeffrey's Ledge and Nantucket Shoals regions.


OBJECTIVES


The Northeast Fisheries Science Center (NEFSC) conducts annual Atlantic Herring acoustic surveys each autumn on the historical spawning grounds of Atlantic herring (Clupea harengus) in the Georges Bank and Gulf of Maine regions. The main goal of this cruise was to provide timely and accurate fisheries-independent estimates of herring spawning stock biomass using state-of-the-art technologies. Operational objectives were to (1) calibrate the EK60 Scientific Sounder, (2) collect acoustic and optic data with the Advanced Fisheries Tow Vehicle, (3) conduct systematic acoustic surveys of selected Atlantic herring spawning stocks, (4) collect in situ target strength data with the EK60, and (5) collect biological data to verify species-specific acoustic measurements using midwater trawls and underwater video.


METHODS


Calibrations and Ambient Noise Tests of the EK60:

Calibrations are required during each survey to ensure data quality and verify echo sounder performance. On the Delaware II, the EK500 was recently replaced with the more advanced EK60 echosounder system. The EK60 was calibrated by suspending standard calibration spheres of known target strength under each transducer from three monofilament lines. A calibration sphere was centered in the far field of each transducer and moved throughout the acoustic beam beneath the vessel using remotely controlled downriggers. The 18-, 38-, and 120-kHz split-beam transducers were calibrated in Cape Cod Bay. Noise tests of the EK60 were conducted dockside and while the vessel was underway at 10 knots (survey speed).


Simrad EK60 Scientific Sounder:

The Simrad EK60 Scientific Sounder was the primary sampling gear used during the acoustic surveys for providing species-specific abundance estimates. The EK60 operated three hull-mounted transducers (18-, 38-, and 120-kHz split-beam transducers). The EK60 was interfaced via TCP/IP Ethernet to the FSV Delaware’s SCS server for data logging. RS232 connections were used for navigational (Differential GPS) input. The SCS Event Log was used to record all operational events (e.g., begin and end points of transects, stations, gear deployments, and other events that affect the track cruise and vessel speed) during the cruise.


Advanced Fisheries Towed Vehicle (AFTV):

The AFTV is designed to deploy integrated acoustical, optical, and environmental sensors for verifying acoustic backscatter from the water column and seafloor. The AFTV is deployed using a portable fiber optic winch system equipped with 2000 m of 0.322 cable, and has an overall weight of about 5,000 lb. The cable has three single mode fiber optic and three copper conductors, and has an 11,000 lb/ft breaking strength rating. The AFTV towbody weighs about 900 lb and is approximately 7 ft in length. The AFTV also has a 100 lb counter weight arranged about 20 m in front of the towbody to dampen the vessel motion for maintaining the horizontal stability of the towbody. This requires a two point deployment approach using the vessel’s A-frame and articulating crane on the aft deck. The AFTV is configured with an EK60 38 kHz, CTD, motion sensor, and various underwater cameras and lighting. The AFTV was towed intermittently at relatively slow speeds (1-3 knots) above the seafloor and throughout the water column to collect in situ target strength data and verify acoustic backscatter.


Dual-frequency IDentification SONar (DIDSON):

A DIDSON sonar was installed on the AFTV during Part I and Part III of the cruise. The DIDSON uses acoustic lens technology to collect very high resolution acoustic data. Using the DIDSON, individual fish and their behavior can be monitored. The DIDSON was located in the forward portion of the AFTV and was mounted on a Sidus pan and tilt assembly to allow for a variety of viewing angles.


Acoustic Survey Operations:

EK60 data were collected continuously throughout the cruise. During the surveys, a constant ship speed of 10±1 knots was maintained. Vessel speed was reduced to no less than 8 knots during rough seas. EK60 operations were generally suspended when seas exceeded 2 m. Each transect was assigned a sequential number throughout the cruise. A transect was defined as a portion of the cruise track with a constant heading and ship speed. All scientific gear deployments were also assigned a unique, sequential deployment number.


EK60 Target Strength Measurements:

Target strength measurements with the hull- mounted EK60 split-beam transducers and with the AFTV-mounted 38-kHz EK60 split- beam transducer (ES38-DD) were collected on selected fish aggregations. The vessel was positioned over aggregations, and the towbody was deployed from the vessel’s aft A- frame while drifting for 30-60 minutes.


Myriax Echoview Post-processor:

Echoview (Myriax Ltd.) software v. 4.7. was used for data acquisition and post-processing of EK60 data during the cruise. Echoview was used to conduct preliminary post-processing of EK60 data at sea, which involved removing extraneous bottom echoes and/or water column noise. Echoview was also used to partition acoustic backscatter to Atlantic herring. EK60 data and Echoview files were logged and archived directly to the SCS system via a TCP/IP Ethernet connection. Three computers were set up for the acoustic data. One computer was used for EK60 data acquisition. This computer was located in the SCS room and was part of the SCS system. The other two computers were set up in the dry lab, with one computer used for post- processing and the other used for viewing data in real time.


Irish Herring Midwater Trawl (IHMT):

The IMHT midwater trawl was used to collect biological samples and verify species composition of acoustic backscatter. The IMHT was designed to be fished at speeds of about 4 knots. The IMHT was deployed during survey operations, and targeted on acoustic backscatter. The IMHT was towed at about 4 knots, depending on trawl performance and water currents. The duration and depth of the trawls were not standardized, and the Chief Scientist or Watch Chief communicated with the bridge officers as to the haul duration and depths. The Simrad FS903 was deployed with every haul. Officers recorded the time, date, navigational, and station data in FSCS, while the scientists recorded the catch and ITI data for each station deployment. Catch data was recorded using the FSCS on-board entry system.


Simrad FS903 Trawl Monitoring and Third-wire Winch System:

The trawl was monitored during fishing operations using the FS903. The Simrad FS903 Trawl Monitoring System was a third-wire device that provided real-time trawl performance information through its sonar images of the trawl opening. The scientific party recorded measurements on hardcopy forms at specified intervals during each deployment.


Scientific Computer System (SCS) and Fisheries Scientific Computer System (FSCS):

The SCS system is a PC-based server, which continuously collects and distributes scientific data from various navigational, oceanographic, meteorological, and sampling sensors throughout the cruise. The SCS Event Log program was configured for NEFSC Fisheries Acoustic Survey operations, and was used by the scientists to document all operational events (e.g., begin and end of transects and deployments). Dates and times were synchronized using the vessel’s GPS master clock and Dimension IV software. The FSCS system was used for on-board data logging of the biological and catch data.


Conductivity-Temperature-Depth (CTD) Profiler:

A Seabird CTD profiler was deployed at the beginning and ending of each transect, and at the beginning of each scientific gear deployment to define the hydrographic conditions in the study area. Water bottle casts were also deployed twice per day to collect salinity samples.


Vemco Minilog Probes:

Temperature-depth probes (set at a 2 sec sampling rate) were attached to the midwater trawl headrope and footrope during trawl hauls.


Biological Sampling:

Trawl catches were sorted by species, weighed and measured (to the nearest cm FL) according to standard NEFSC procedures. For Atlantic herring, subsamples were taken for each trawl haul for detailed lengths (FL in mm), individual weights (to nearest 0.1 g), sex/maturity staging, and otolith samples (freeze herring whole). Subsampling protocol was 1 fish per centimeter length class for herring less than 25 cm and 3 fish per centimeter length class for herring 25 cm and longer. The FSCS system was used for on-board entry and auditing of trawl station and biological data. Biological data were transferred to the NEFSC for auditing.


RESULTS


Part 1

Part 1 was dedicated to calibrating the hull-mounted EK60 transducers, collecting data with the Advanced Fisheries Tow Vehicle (AFTV), and conducting a systematic survey of Atlantic Herring on Georges Bank. The AFTV was loaded on the Delaware II, and initial testing, trouble shooting, and evaluation was completed on the 8th and 9th of September. A test deployment of the AFTV was conducted on 9 September to educate new deck crew members on the intricacies of deploying and retrieving the AFTV. The Delaware II departed the Fisheries dock on Sept. 12 after repairs were made to the vessel, and headed to Cape Cod Bay to calibrate the EK60.


The 18-, 38-, and 120-kHz EK60 echo sounders were successfully calibrated in Cape Cod Bay. Sv and TS gain setting changes were within tolerance levels (± .25 dB). A CTD profile was collected at the calibration site. The calibration site was located about five miles southwest of Provincetown, MA. After the calibrations, the vessel steamed to Georges Bank to begin the systematic survey of Atlantic Herring. The survey consisted of parallel transects oriented in a North to South direction with 8 nmi spacing between transects (Fig. 1). CTD profiles were conducted at the beginning and ending of each transect, with water samples taken twice daily. The AFTV was deployed once on 14 September. We were able to collect good data with the onboard EK60 transducer, video, and the DIDSON sonar systems. During the retrieval process, the towbody bounced off of the side of the rear deck well which in turn damaged some electronics internal to the AFTV. The towbody could not be repaired on the boat, so any further AFTV deployments were canceled. At the conclusion of the survey, the Delaware II steamed back to Woods Hole and arrived the morning of Sept. 17. The AFTV was offloaded so that repairs could be made prior to the start of Part 3 of the Herring survey.


During this portion of the cruise 46 deployments (1 AFTV, 33 CTD, and 12 trawl deployments) and 21 transects were completed.


Part 2

The goal of Part 2 was to conduct the annual systematic acoustic survey of Atlantic herring along the northern edge of Georges Bank and southern Gulf of Maine. Survey operations included EK60 acoustic data acquisition, midwater trawl hauls, and CTD profiles. The vessel departed Woods Hole on Sept. 21 and steamed to the northeast peak of Georges Bank. The vessel arrived on station on Sept. 22 and commenced the survey (Fig. 2). The survey consisted on parallel transects oriented north-south with 8 nmi spacing between transects. Survey speed was consistently 10±1 knots. CTD profiles were completed at the beginning and end of each transect and immediately prior to or immediately after each trawl haul. Trawl location were selected on an ad hoc basis to sample the acoustic backscatter.


Due to weather conditions, the survey on Georges Bank was suspended on Sept. 27 and we steamed to Jeffreys Ledge to begin a systematic survey. This survey commenced on Sept. 28 and consisted of parallel transects oriented east-west with 4 nmi spacing between transects. On Sept. 29, the weather calmed down enough to go back to Georges Bank to reconvene that survey. On Oct. 2, this survey was suspended due to the end of the leg.


This portion of the survey was completed on Oct. 2, with a total of 36 trawls, 67 CTD profiles and 38 transects (parallel and crossover) completed.


Part 3

The first portion of Part 3 was dedicated to completing the herring survey in Georges Bank and Jeffrey's Ledge (Fig. 3). On October 2nd, the AFTV was loaded back onto the Delaware II, and all systems were tested. The vessel departed Woods Hole on October 6th. Due to unfavorable seas on Georges Bank at the start of Part 3, we began the survey on Jeffrey's Ledge to finish up transects from Part 2 of the survey. This survey consisted of parallel transects, oriented east to west, with 4 nmi spacing between each parallel transect. CTD profiles were collected at the beginning and ending of each transect, with a water sample taken twice daily. We completed all transects on Jeffrey's Ledge on the evening of October 8th. During this portion of the survey, we completed 19 CTD profiles, and 8 IHMT trawls.


We then steamed to Georges Bank to finish up the transects that were left from Part 2 of the survey. We arrived at Georges Bank on 9 October, and commenced parallel transects. We finished this portion of the survey on the Great South Channel on 12 October. This concluded all of the transects that were part of the annual systematic Atlantic Herring acoustic survey. During this portion of the survey, we completed 22 CTD profiles, 1 AFTV deployment, and 13 IHMT trawls.


With the Atlantic Herring survey completed and the weather conditions deteriorating on Georges Bank, we proceeded to the Nantucket Shoals area to conduct a mini survey of Atlantic Herring distribution in this region. We began this mini survey on 12 October, performing parallel transects in an East to West direction, with 4 nmi spacing between transects. We finished this mini survey on 13 October, with 13 CTD profiles, 3 AFTV deployments, and 6 IHMT trawls completed.


Since the weather was improving along Georges Bank, we decided to steam back to Georges Bank to continue investigating the herring distribution along the bank. We were able to complete two south – north parallel transects before time ran out. We completed 5 CTD profiles, and 3 IHMT trawls during this portion of the survey. The Delaware II commenced steaming back to Woods Hole in the morning of October 15, arriving back at Woods Hole on the 16th of October.


This survey was completed on Oct. 15, with a total of 30 trawls, 59 CTD profiles, 4 AFTV deployments, and 21 transects completed during Part III.


DISPOSITION OF DATA


Data and results were archived at the Northeast Fisheries Science Center (NEFSC). Data and results are available on CD-ROM or other media. Cruise reports and results are also available at the NEFSC website:

http://www.nefsc.noaa.gov/femad/ecosurvey/acoustics/



SCIENTIFIC PERSONNEL


National Marine Fisheries Service, NEFSC, Woods Hole, MA

Michael Jech

Research Fisheries Biologist

Parts 1, 2, 3

(Chief Scientist - Parts 1)

Joseph Godlewski

Electronics Engineer

Parts 1, 3

(Chief Scientist - Part 3)

Richard Raynes

Gear Specialist

Part 1

Takashi Arbusto

Gear Specialist

Part 2

Robert Gamble

Operations Research Analyst

Part 3


Contractors, NEFSC, Woods Hole, MA

Francine Stroman

Fisheries Biologist

Parts 1, 2, 3

(Chief Scientist - Part 2)

Tyler Staples

Fisheries Liaison

Part 2


City University of New York, New York, NY

Marie-Caroline Martin

Graduate Student

Parts 1, 2, 3

Holly Goyert

Graduate Student

Part 1

Timothy P. White

Graduate Student

Parts 2, 3


Volunteers

Caroline Robinson

Dover, NH

Part 1

Sara Melton

Washington, DC

Part 1

Kate Mulvaney

Washington, DC

Part 2

Rebeca Rant

Newmarket, NH

Part 2

Per Rudstam

Ithaca, NY

Part 2

Judy Mandle

Harrington, CT

Part 3

Alex Ware

Manchester, MA

Part 3



Part 1: 12 - 17 September 2009

Part 2: 21 September - 2 October 2009

Part 3: 6 - 15 October 2009


For further information please contact: Michael Jech, National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, Massachusetts 02543-1097. Telephone (508) 495-2000.

Email: Michael.Jech@noaa.gov


Graphic showing area of operations and cruise tracks for Part 1 of Herring Survey DE 09-10.

Figure 1. Part 1 (September 12-17, 2009) area of operations and cruise track for DE200910, Atlantic Herring Acoustic Survey.


Graphic showing area of operations and cruise tracks for Part 2 of Herring Survey DE 09-10.

Figure 2. Part 2 (September 21 to October 2, 2009) area of operations and cruise track for DE200910, Atlantic Herring Acoustic Survey.


Graphic showing area of operations and cruise tracks for Part 3 of Herring Survey DE 09-10.

Figure 3. Part 3 (October 6-15, 2009) area of operations and cruise track for DE200910, Atlantic Herring Acoustic Survey.




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