NOAA Protocols for Fisheries Acoustics Surveys and Related ...

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Bubble Attenuation Vessel speed is reduced when heavy seas cause substantial bubble sweep down along the hull and across the transducer face (although slowing the vessel reduces bubbles caused by the pounding of the hull but not by the waves themselves). In extreme weather, survey operations are suspended. However, if surveying in areas where landmasses can offer protection from severe weather, operations are moved into protected areas, and survey operations in the exposed areas are resumed when the weather subsides. Most noise caused by bubble sweep down is excluded during post processing. No attempt is made to correct for bubble attenuation. Transducer Motion Vessel speed is reduced when transducer motion becomes excessive, which helps during extreme pitching but not during extreme rolling. In severe weather, survey operations are suspended. If land masses can offer protection from severe weather, operations are moved into protected areas, and survey operations in the exposed areas are resumed when the weather subsides. Bio-fouling The NOAA Ship Miller Freeman is moored in fresh water between field seasons, which suppresses the growth of any saltwater organisms (e.g. barnacles) on the transducer face. Transducers are inspected (and cleaned, if necessary) during most sphere calibrations before a survey is started. Target Strength (σ i ) Target strength (TS) describes the acoustic reflectivity of a single target. The measurement is needed to scale acoustic estimates (e.g., volume backscattering) into numbers or weight of the target species per unit area. A more detailed description of target strength is presented in the National TS Protocol section. Dedicated efforts at AFSC to collect TS measurements have been directed at fishes. Thus, the following AFSC Regional TS sampling protocols refer to situations where fishes not invertebrates are the target species. As discussed in the National TS Protocols section, TS measurements can be collected on either immobile fish, fish confined to a cage (ex situ), or free-swimming fish in their natural habitat (in situ). The focus at AFSC has been to collect in situ TS measurements, and attempts to do this are routinely made during AFSC acoustic – trawl surveys. The measurements are used to assess whether modifications should be made to the currently accepted model, which describes the TS to fish length relationship for walleye pollock (Traynor 1996). Models Definition & Importance The model that is currently used to describe the relationship between walleye pollock fork length (L) and TS is TS = 20 log L – 66 (Traynor 1996). The data used to generate the model were in situ TS data collected at 38 kHz from dual-beam and split-beam systems as well as estimates from swimbladder morphology studies. Several other species, besides walleye pollock, 92
are often detected acoustically during AFSC acoustic-trawl surveys (e.g., Sebastes spp., Myctophidae, Osmeridae). Few TS to length relationships have been described for these other species (e.g., Stanley et al. 2000; Benoit-Bird et al. 2001). With the exception of eulachon (Thaleichthys pacificus (Osmeridae)), however, these other species can be discriminated acoustically from the target species, walleye pollock, based on echosign morphology. Research is currently underway to describe the TS to length relationship for eulachon. This information will enable the echo integration data to be more accurately partitioned between pollock and eulachon based on the catch composition of these species and following methods described in MacLennan and Simmonds (1992). Techniques Validation Additional in situ TS observations at fish lengths where data are sparse or non-existent (i.e.,
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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
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 58 and 59: S v Calibrations The NEFSC acoustic
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 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 118 and 119: Biological Data Data from catch pro
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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