NOAA Protocols for Fisheries Acoustics Surveys and Related ...

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S v Calibrations The NEFSC acoustics manual (NEFSC_aqstx-acoustics_manual.doc) details S v calibration protocols. The tolerance of the 38-kHz S v calibration is ±0.4 dB (G 0 : ±0.2 dB). Transceiver settings are equivalent to those used during the survey. Oceanographic Data A vertical temperature and salinity (CTD) profile is collected prior to calibrations that are conducted offshore. For inshore calibrations, such as those that are conducted at the Woods Hole Oceanographic Institution’s pier, either CTD profiles or the 3-m temperature and salinity hull-mounted sensor are used for the physical data. CTD profiles encompass the calibration depths. Refer to the Sampling->Oceanographic Data section for details on operating the CTD. Temperature and salinity measurements are compared between the CTD profiler and hullmounted sensors during the calibrations. Considerations Remediation If the 38-kHz TS or S v gain values (G 0 ) are outside of the tolerances defined above, the survey will not commence until the cause of the error is resolved. The Simrad manual (Simrad, 1996) provides diagnostic tests to evaluate the EK500 echo sounder. If temperature and salinity measurements are not comparable between the CTD profiler and hull-mounted sensors, the Fisheries Oceanography Investigation (FOI) and the ship’s electronic technician should be contacted to determine the cause of the discrepancy. System Performance Techniques The ‘test’ values and passive noise values for the Simrad EK500 echo sounder are documented for every calibration and at the beginning of each survey ‘leg’ (two-week portion of a survey). Test and passive noise values are documented for the 18, 38, and 120-kHz frequencies. During the survey, individual target locations in the acoustic beam (EK500 TS Detection Menu) are evaluated to ensure that individual target locations appear in all quadrants. Considerations Remediation Survey operations should be suspended if the ‘Test’ values are out of tolerance and the cause of the errors diagnosed. The Simrad manual provides diagnostic and evaluation procedures (Simrad, 1996). After the problem is resolved, the survey can continue. If individual targets do not appear in all quadrants, survey operations should be suspended and the problem diagnosed. After the problem is resolved, the survey can continue. Data Management The calibration LOBE data, EK500 telegram data, parameter settings, and associated metadata are stored on board until such time is appropriate for downloading to a shore-based computer. The LOBE data are stored on the laptop computer that was used for the calibrations. The EK500 telegram data are stored on the backup SCS server, which is RAID configured to 58
minimize potential loss of data. These data are archived by the Data Management Service branch at the NEFSC after the data are downloaded to shore. Volume Backscattering Measurements (E i ) Data Collection Techniques Echo Sounder Parameters Echo sounder parameters are set relative to the goals of the survey and in some cases are a compromise between data quality and preferred values, where data quality has paramount priority. Transceiver settings for the Simrad EK500 echo sounder are provided in Table 2. The S v gain (G 0 ) is obtained from the echo sounder calibration (Calibration section). Simrad provides the power and two-way integrated beam pattern and these values are not modified unless a transducer is changed. The sound speed and sound attenuation are not modified from the default values for the fall Atlantic herring survey. The bandwidth value (‘auto’) is set according to the Simrad recommendations. The pulse durations for the 38-kHz and the 120-kHz systems are set equivalently (i.e., the ‘medium’ 38-kHz pulse duration is equivalent to the 120-kHz ‘long’ pulse duration) as per the recommendation of Demer et al. (1999) for improving acoustical discrimination of individual targets using multi-frequency methods. The 1 ms pulse duration was chosen for the 38-kHz echo sounder as the optimal setting for the depth ranges encountered during the fall Atlantic herring survey (maximum range of approximately 500 m) and the vertical resolution of the integrated data (1 m). The ‘medium’ pulse durations of the 12 and 18-kHz systems were chosen to avoid poor performance detected at the ‘short’ setting. Table 2. EK500 echo sounder transceiver parameter settings. Frequency Sound Speed Pulse Length Bandwidt Power [kHz] [m s -1 ] h [Watts] 12 1500 Medium (3.0) Auto -15.8 1 4000 18 1500 Medium (2.0) Auto -16.9 3 2000 38 1500 Medium (1.0) Auto -15.8 10 1000 120 1500 Long (1.0) Auto -20.7 38 1000 is the two-way integrated beam pattern [dB], and is the sound attenuation [dB m -1 ]. The pulse length is given as the Simrad setting (Medium or Long) and the duration (given in milliseconds). Note the 12-kHz echo sounder was replace by the 18-kHz echo sounder in 2002. The echo sounder is calibrated with the same transceiver settings used during the survey, and the transceiver settings are not modified during the survey. Other EK500 echo sounder parameters for S v data collection are provided in Table 3. These parameter settings are common among all frequencies (12, 18, 38, and 120 kHz). Parameters not listed in Table 3 are left to the discretion of the operator and do not affect data collection. Table 3. EK500 echo sounder S v data collection parameters. Parameter Setting Operation Menu/Ping Auto Start Off Operation Menu/Ping Interval 2.0 59
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NOAA Protocols for Fisheries Acoust
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Echo Sounder Parameters ...........
Page 6 and 7:
Trawls ............................
Page 9: Introduction In response to Vice Ad
Page 12 and 13: Advanced Survey Technologies Progra
Page 14 and 15: Techniques Before conducting a cali
Page 16 and 17: Considerations Remediation Echo sou
Page 18 and 19: transmission loss. To correct for s
Page 20 and 21: unavoidably discarded, just as some
Page 22 and 23: factors such as orientation are not
Page 24 and 25: A schedule for calibration and main
Page 26 and 27: Techniques Noise Acoustical A commo
Page 28 and 29: ⎛ I ⎞ r TS ≡ 10 log10 ⎜ ⎟
Page 30 and 31: Considerations Remediation If a TS-
Page 32 and 33: Techniques Beam Pattern Transducers
Page 34 and 35: during vertical migration, will cau
Page 36 and 37: A schedule for calibration and main
Page 38 and 39: degradation are external to the ech
Page 40 and 41: permanently archived for each surve
Page 42 and 43: Numerical Density to Biomass Densit
Page 44 and 45: An electronic ‘event log’ can b
Page 46 and 47: References Demer, D.A., M.A. Soule,
Page 48 and 49: Regional Protocols Because of the d
Page 51 and 52: Table of Contents Introduction.....
Page 53: Electrical ........................
Page 56 and 57: Center Background NEFSC The Northea
Page 60 and 61: Operation Menu/Transmit Power Norma
Page 62 and 63: Software The echo sounder firmware
Page 64 and 65: ii. Minimum Sv for good pick: -50.0
Page 66 and 67: Net mensuration sensors are attache
Page 68 and 69: We remove backscattering by surface
Page 70 and 71: GPS The primary Global Positioning
Page 72 and 73: Electrical Electrical noise protoco
Page 74 and 75: Scientific Computer System (SCS) Fi
Page 77: Appendix 2 March 11, 2005 NOAA Prot
Page 80 and 81: Techniques ........................
Page 82 and 83: Center Background AFSC The Alaska F
Page 84 and 85: On-axis sensitivity and S v calibra
Page 86 and 87: Volume Backscattering Measurements
Page 88 and 89: Mid-water juvenile pollock (max sa=
Page 90 and 91: Biological Sampling Mid-water and n
Page 92 and 93: Bubble Attenuation Vessel speed is
Page 94 and 95: Data Collection Since 1990 to the p
Page 96 and 97: sampling resolution of scattering l
Page 98 and 99: A decision must be made as to wheth
Page 100 and 101: design. If fish abundance in this a
Page 102 and 103: Simrad. 2001. Simrad EK60 scientifi
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Page 106 and 107: Acoustic Data......................
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ackscattering cross-section (σ i )
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o For the 38 kHz transducer operati
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• Two-way integrated beam pattern
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Classification Techniques Single Fr
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Performance Degradation Definition
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Biological Data Data from catch pro
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elation also assumes that backscatt
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finer than the 13.5-18.9 nmi (25-35
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Improvements - The annual hake migr
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Techniques The primary source of th
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Hamano, A., Sasakura, T., Kieser, R
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