bioacoustics 93mar 03apr93-09may93 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 to three short (1-2 km) acoustic transects were conducted in conjunction with net tows at each Palmer LTER station occupied during a cruise. 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 consists of a BioSonics Model 102 echo sounder connected to a downward looking 120 kHz transducer which was deployed with a tow body several meters below the surface. The two body was deployed either with the research vessel RV Nathaniel B. Palmer. Echo integration of the returned acoustic energy was done with the BioSonics Model 221 Echo Signal Processor, and ESP version 2 (1990). The system was configured to integrate voltage measurments 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) recorder. The DAT tapes were 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 collection of the data (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) ¥ removal 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 93mar and a krill length frequency distributions matched to acoustic transects were used to estimate the target strength distribution (4) calibration of the system was done by BioSonics ( Seattle, WA) on with the original rented deck/tow cables in a tank. Acoustic measurements were made along several short (1-2 km) transects which were centered over a discrete location. Transects were conducted within 4 hours of the time other LTER data sets were collected. Each acoustic transect was matched with a net tow to allow identification of potential scatterers and the size distribution of Euphausia superba, the dominant scatterer. Antarctic krill are usually the dominant sound scatterer in the Southern Ocean. However salps were common in the northern section of the region this cruise. Test trials are not included. bioacoustics, acoustic biomass, antarctic krill, palmer lter ascii space delimited (number of columns) the same number of rows shows the column headers with R (real) or I (integer) and the units of the parameter data follow ~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) acoCalib.dat calibration information. used by post-processing software (3) acoMatchMulti.dat associated event numbers for each acoustic event; net samples with length frequency distributions (4) swarmHdr.dat aggregation transect parameters for each event, including average biomass (g per m^2) over the transect Robin M. Ross, Langdon B. Quetin Eileen E. Hofmann Robin M. Ross, Langdon B. Quetin UCSB (S-028), Old Dominion teams Cathy Lascara Cathy Lascara, Ph. D. thesis (1996) Langdon B. Quetin 31 December 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. The data are being reformated to include a standard file for each study; acoBiomass.dat is the vertically integrated average acoustic biomass for each transect in grams per m^2. There will be 7 variables: Event number, Station (Palmer LTER grid location), Date (MoDaYr), Time (GMT, HrMin), TransectLength (km), MeanBiomass (g/m^2)

Datafile Form V1.2 for describing a data file.