Sardine Acoustic Attenuation and Target Strength Experiment in South African Waters, False Bay, 21-29 April 2002.Entry ID: NatMIRC_20020614_13208
Abstract: Data on attenuation and target strength were collected on a
survey carried in South African water, False Bay on the 21st to 29th
April 2002. Two EK500 echosounders (Ver. 5.30) firing through the
keel-mounted split-beam transducers operating at nominal frequencies
of 18, 38, 120 kHz (EK1) and a single-beam transducer at 200 kHz (EK2)
were utilized. Data were logged continuously during the ... experiments
utilizing both Sonardata_Echolog (Ver. 2.00.21) and Bergen Echo
Integrator (BEI) (Sun Unix) logging platforms.
The Simrad SA950 sonar was manned and the vessel was manoeuvred over
schools in order to obtain as many samples as possible for attenuation
experiment. The schools used in the analysis were discrete and
mono-specific and in areas where no significant amounts of scattered
fish occurred. A school was defined as the area encompassed by echoes
when the SV threshold was raised to 65 dB. The signal below the school
was not removed, as this was likely to contain part of the multiple
scattering echo or 'tail'. The bottom echo in the vicinity of the
school was analysed to determine whether there was a significant
reduction in the bottom echo under the school compared to either side
of the school.
Data on sardine target strength were collected at three frequencies;
38 kHz, 120 kHz and 200 kHz. Prior to collecting target strength data
a trawl was conducted to ensure that the species composition was
largely sardine. Up to approximately 10% of other species was
permitted in the sample.
Raw EK500 exported data were copied onto CD`s and distributed to
Angola, MCM and MFMR personnel for deposition in their relevant data
centres. A copy of all data was also stored in the on-board BEI
(Click for Interactive Map)
Data Set Citation
Dataset Originator/Creator: Ministry of Fisheries and Marine Resources
Dataset Title: Sardine Acoustic Attenuation and Target Strength Experiment in South African Waters, False Bay, 21-29 April 2002.
Data Presentation Form: None
Start Date: 2002-04-21Stop Date: 2002-04-29
Quality The data were to be sampled in Namibian water. However, the
data were sampled in South African water becuase of low biomass
estimate repoted prior to this experimental survey in Namibia.
Access Constraints Release with permission of the appropriate parties
Use Constraints prior permission should be obtained from the
Permanent Secretary of Ministry of Fisheries and Marine Resources.
Data Set Progress
Distribution Media: CD-ROM
Distribution Format: Not Known
Role: DIF AUTHOR
Email: btjizoo at mfmr.gov.na
P. O. Box 912 Swakopmund
Creation and Review Dates
DIF Creation Date: 2002-06-14
Last DIF Revision Date: 2004-03-10