bioacoustics 9192pal 11dec91-27feb92 Vertically integrated acoustic biomass averaged over the transect distance. The vertical extent is from about 10 m below surface (varies with study) to 200 m or the bottom, whichever is shallower analog voltage signal The primary derived variable is acoustic biomass. Two acoustic transects of about 3.5 to 5 km each were conducted weekly, from Arthur Harbor out to the 200 m contour line (A-E), and on the east side of Wylie Bay, along the outside of the islands (Humble to Spume Islands) near Palmer Station and within the 3.7 km boating limit (F-J). The Palmer LTER uses Biosonics equipment to collect hydroacoustic data, and several software programs to analyze the data. (1) collection of data The acoustic system consisted of a BioSonics Model 102 echo sounder connected to a downward looking 120 kHz transducer on a tow body. The tow body was deployed with a Mark V zodiac 1 m below the surface. Echo integration of the returned acoustic signal was done with the BioSonics Model 221 Echo Signal Processor, and ESP version 2 (1990). The system was configured to integrate voltage measurements over 2-m depth intervals and several pings. These integrated values were used to generate a two-dimensional matrix of volume scattering data (VSD, m^2 m^-3) for each acoustic transect, according to algorithms described in Appendix C of BioSonics (1990). (2) archival process The analog voltage signals received by the echosounder are processed in the field through an interface tape unit which records a digitized version of each signal onto a digital audio tape (DAT). The DAT tapes can be replayed with the Biosonics Echo Signal Processing (ESP) software package for calculation of Sum Squared Voltage (SSV) data. (2) primary processing of data: echo integration of the returned signal was done with the BioSonics software ESP v 2. (1990) during playback of the DAT tapes at UCSB, using the bottom algorithm to eliminate bottom return. (3) post processing included: removal of a background noise level of -81 decibels (dB) from all acoustic observations; this is equivalent to 0.05 g m^-3 of krill biomass (Lascara, 1996) moval of acoustic scattering produced by abiotic factors such as sea ice, air bubbles, wave action at the surface, ocean bottom, and acoustic noise from ship or zodiac equipment; this removal process is faciliatated by notes taken on sea ice, wind speed etc. during the collection of the data. use of a target strength relationship used to convert echo integration data to acoustic biomass (mg/m^3) TS120 (target strength at 120 kHz) = -98.64 + 10.28 logWWt (wet weight) was based on the empirical relationship of Wiebe et al (1990) as modified by Greene et al. (1991) for 120 kHz. the length-weight regression from 91 Nov and a standard krill length frequency distribution was used to estimate the target strength distribution (4) calibration of the system was done by BioSonics ( Seattle, WA) in a tank on 11 Oct 1991 with the original rented deck/tow cables. BeamPatternFactor 0.002653 Rcvr1_G120logR -156.568 Rcvr1_G140logR -185.413 Rcvr2_G120logR -157.599 Rcvr2_G140logR -186.320 Rcvr3_G120logR -160.122 SrcLevel_at0dB 222.459 SrcLevel_at-3dB 219.397 SrcLevel_at-6dB 216.688 SrcLevel_at-10dB 212.832 SrcLevel_at-13dB 209.950 20/40CrossoverPt 27.686 Acoustic transects were done within 6 hours of a series of LTER stations along the same transect. Data from these stations includes hydrographic, optical, and pigment. Targeted tows in the same week confirmed the composition of possible acoustic scatterers. Antarctic krill are usually the dominant sound scatterer in the Southern Ocean. Target and standard tows during the week verify the composition of the dominant scatterers. During 9192pal Antarctic krill were the dominant scatterer present. Test trials are not included in acoEvent.dat. Evt27 (bad recording) and evt 229 (caltone error) are not included in acoBiomass.dat. Events 15201 and 15202 are different acoustic transects run on the same day, the first on A-E and the second on F-J. bioacoustics, acoustic biomass, antarctic krill, palmer lter ascii, comma separated variable format (number of columns)! (study name) one row per column with the column header, R (real) or I (integer), and the units of the parameter data follow in csv format ~lter/lterdata robin's mac (1) acoEvent.dat is a listing of acoustic events with information gathered both from the acoustic transect record and each Biosonics rawdata file, i.e. set up and sounder parameters in addition to counts of strata etc. There are 27 variables: event number, strata record count (StrCnt, from Biosonics file) and horizontal cell record count (RecCnt, from Biosonics file), total distance (TotDist, km calculated from start and end positions) and time (TotMin, minutes), cell length (meters, calculated from Distance*1000/event.RecordCnt), starting (S) and ending (E) date (MonthDayYear), time (GMT HrMin), latitude (lat, degrees) and longitude (lon, degrees), julian day (jday) and minute (jmin), a flag to control the value of the multiplier field which is used during the computation of VSD (TvgFlag, 0-no correction needed, 1-convert 40 to 20logR), total pings for this tow (TotPings, from Biosonics file), the sounder source level (SrcLvl, from Biosonics file), receiver gain of echosounder during data collection (Rgain, db, from Biosonics file), pulse width (ms, pulse width of echosounder, from Biosonics file), speed of sound (Sos, m/sec, from Biosonics file), BlankDist (distance to starting strata from face of transducer, meters, from Biosonics file), transducer offset (TransOffset, meters, from Biosonics file), and station (grid designator for station location, e.g. 624.038). (2) acoBiomass.dat is the vertically integrated average acoustic biomass for each transect in grams per m^2. There are 7 variables: Event number, Station (Palmer LTER grid location), Date (MoDaYr), Time (GMT, HrMin), TransectLength (km), MeanBiomass (g/m^2), NearshoreTransectID (A-E = 1; F-J=2; Bismarck=3; Palmer Basin = 4) Transect length is calculated as the sum of the distances of the segments with recorded locations for beginning and ends. Usually there were 4 segments in a slightly curved transect. Robin M. Ross, Langdon B. Quetin Cathy M. Lascara Robin M. Ross, Langdon B. Quetin Tim Newberger with the assistance of Robin Ross, Phil Handley, Karen Haberman, Karen Hacecky, Jacqeline Mahoney, Margaret Amsler Tim Newberger replayed the DAT tapes and did the primary processing at UCSB; Tim Newberger and Cathy Lascara did the post- processing. Janice Jones revised the transect length data by calculating the sum of the segments. Tim Newberger, Cathy M. Lascara, Robin M. Ross Robin M. Ross and Langdon B. Quetin Langdon B. Quetin 29 Dec 1996 BioSonics (1990) BioSonics Echo Signal Processor Operators Manual. BioSonics, Inc., Seattle, WA, 373 pp. Lascara (1996) Seasonal and mesoscale variability in the distribution of Antarctic krill, Euphausia superba, west of the Antarctic Peninsula. Ph. D. Thesis, Old Dominion University. 167 pp. Greene, C. H., T. K. Stanton, P. H. Wiebe and S. McClatchie (1991) Acoustic estimates of Antarctic krill. Nature 349: 110. Nero, R. W. and J. J. Magnuson (1989) Characterization of patches along transects using high resolution 70 kHz integrated acoustic data. Canadian Journal of Fisheries and Aquatic Sciences 46: 2056-2064. Wiebe, P. H., C. H. Greene, T. K. Stanton and J. Burczynski (1990) Sound scattering by live zooplankton and micronekton: empirical studies with a dual-beam acoustical system. Journal of Acoustical Society of America 88: 2346-2360. Yearly calibrations are conducted to ensure that the equipment has not changed markedly during the period of use.

Datafile Form V1.2 for describing a data file.