NOAA Protocols for Fisheries Acoustics Surveys and Related ...

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Biological Data Data from catch processing and haul operations are recorded to PCs during a survey. Catch, haul, length, and specimen files should be backed up routinely onto external hard drives or networked servers. Files can also be burned onto CD or DVD for added redundancy. Upon survey completion, these files are permanently archived onto an Oracle server at the Seattle FRAM facility after undergoing a battery of error checks. Oceanographic Data Vertical profiles of temperature and salinity collected with conductivity-temperature-depth (CTD) systems and temperature and depth profile data collected from portable, microbathythermographs are recorded to PCs during a survey. Ocean current velocity profile data from Acoustic Doppler Current Profilers (ADCP) are also written to a PC. Oceanographic data should be backed up routinely onto external hard drives or networked servers during a survey. Data can also be burned onto CD or DVD for added redundancy. Upon survey completion, all files are downloaded to a server in the Seattle FRAM facility. An Oracle-based adatabase for oceanographic data has yet to be developed. Currently, post-cruise quality control/quality assurance procedures and analysis of these data are done in collaboration with partners in the oceanographic field, e.g. at Oregon State University and/or DFO, Institute of Oceanographic Sciences. Protocol 3 – Target Strength (σ i ) Models The backscattering characteristics of detected Pacific hake, required to scale the measured volume backscattering (see Protocol 4), are predicted by applying an empirically derived TSlength relation to the appropriate size distribution of sampled fish. In situ measurements are not used owing to the combination of depth (distance from the transducer) and the rather high densities Pacific hake aggregations typically exhibit during survey conditions (see Techniques section and Improvements section, below). • The Traynor (1996) relation of backscattering to fish size for Pacific hake at 38 kHz is given as TS dB = 20 log L − 68 , where TS dB is target strength in decibels and L is fish length in centimeters. The following are conventions to be followed: • Target strength (TS), the logarithmic form of the measured backscattering cross section ( σ bs), is given as: ( ) dB re1 Pa TS ≡ 10log10 µ σ bs 118
in Maclennan et al. (2002). • Backscattering cross section is further distinguished from omni directional or spherical scattering cross-section by: σ = 4πσ sp bs where the 4π term must be included in the scaling of volume backscattering by σ bs when applied to nautical area scattering coefficient (m 2 /nm 2 ), denoted as s A (Maclennan et al., 2002). Techniques The expected backscattering cross section ( σ bs ) for a given assemblage of Pacific hake is based on the empirical relation suggested by Traynor (1996) as: σ bs = ∑ j f ij {[ −68+ 20logL ]/10} 10 ij for the frequency f of length L of the length class i in composite catch sample j . Validation – To date, the empirical equation reported by Traynor (1996) represents the best understanding of in situ backscattering properties of Pacific hake that relates target strength to fish length at 38 kHz. This work represents an extension of initial in situ measurements on Pacific hake made by (Williamson and Traynor, 1984). These and other studies that attempt to define the in situ target strength characteristics of Pacific hake (e.g. Hamano et al., 1996) all suffer from the ability to find appropriate day and nighttime concentrations of hake at moderate depths. Collectively, these studies are consistent within their results, though variability in their measurements suggests further refinements are in order. Error Error in the predicted TS values will affect the overall uncertainty in the derived abundance estimates. While this error will never be eliminated, the degree that variability in backscattering characteristics that occurs should be recognized in view of the resulting level of tolerance of error based on survey goals. Under typical survey conditions, MacLennan and Simmonds (1992) suggest error in TS may range 0 – 50%, which at the upper end, may contribute extensively to the overall error budget. One source of potential error in predicted TS from application of the Traynor (1996) equation is the inability to incorporate effects on backscattering from changes in behavior and vertical distribution of Pacific hake. The conditions that characterized the hake during the acquisition of the in situ measurements and used to develop the relation must necessarily be assumed to be the same for subsequent application in any given survey – deviations from those behaviors present in the fish used in developing the relation (e.g., tilt angle distributions) and those encountered during a survey will induce errors in the length-specific predicted TS values. Moreover, this 119
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NOAA Protocols for Fisheries Acoust
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Echo Sounder Parameters ...........
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Trawls ............................
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Introduction In response to Vice Ad
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Advanced Survey Technologies Progra
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Techniques Before conducting a cali
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Considerations Remediation Echo sou
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transmission loss. To correct for s
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unavoidably discarded, just as some
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factors such as orientation are not
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A schedule for calibration and main
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Techniques Noise Acoustical A commo
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⎛ I ⎞ r TS ≡ 10 log10 ⎜ ⎟
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Considerations Remediation If a TS-
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Techniques Beam Pattern Transducers
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during vertical migration, will cau
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A schedule for calibration and main
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degradation are external to the ech
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permanently archived for each surve
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Numerical Density to Biomass Densit
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An electronic ‘event log’ can b
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References Demer, D.A., M.A. Soule,
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Regional Protocols Because of the d
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Table of Contents Introduction.....
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Electrical ........................
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Center Background NEFSC The Northea
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S v Calibrations The NEFSC acoustic
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Operation Menu/Transmit Power Norma
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Software The echo sounder firmware
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ii. Minimum Sv for good pick: -50.0
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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......................
Page 108 and 109: ackscattering cross-section (σ i )
Page 110 and 111: o For the 38 kHz transducer operati
Page 112 and 113: • Two-way integrated beam pattern
Page 114 and 115: Classification Techniques Single Fr
Page 116 and 117: Performance Degradation Definition
Page 120 and 121: elation also assumes that backscatt
Page 122 and 123: finer than the 13.5-18.9 nmi (25-35
Page 124 and 125: Improvements - The annual hake migr
Page 126 and 127: Techniques The primary source of th
Page 128 and 129: Hamano, A., Sasakura, T., Kieser, R
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