NOAA Protocols for Fisheries Acoustics Surveys and Related ...

Considerations
Remediation
Echo sounder manufacturers should provide detailed diagnostic and evaluation routines.
General diagnoses for the EK500 are:
The ‘test’ values for the EK500 are a measure of the transducer performance and are
acquired for each transducer. A ‘test’ value not within the specified tolerance (refer to the
Simrad EK500 manual for values and tolerances) is an indication of a broken connection in one
or more of the wires to the transducer. Impedance and continuity tests should be performed to
determine which wires are severed, and the connections must be repaired. The cause of the
broken connection should be determined and rectified.
If the TS and/or Sv gains (G 0 ) are not within tolerance, ‘test’ values (for the EK500) may
indicate a problem with the transducer or transducer cable. If this is not the problem, then a full
set of diagnostics must be completed on the echo sounder to determine the cause of the problem.
The survey should not continue until the problem is rectified.
Improvements
Improvements in calibrations include the ability to measure the angular location of the target
independent of the echo sounder.
System Performance
Definition & Importance
System performance is the evaluation of echo sounder and transducer performance during a
survey.
Periodic monitoring and evaluating of system performance is necessary for ensuring highquality
acoustical data during surveys. System performance deals with the internal electronics
and processors and transducer and cable, not with interference introduced from external sources
(System Degradation section).
Techniques
Error
Reduced or variable system performance will affect target strength and volume scattering
measurements, and ultimately population estimates. Systematic errors in system performance
include a change in transducer sensitivity over time or with other shipboard operations. Random
errors can be very difficult to diagnose, but every effort should be made to diagnose the
problems. If systematic and/or random errors are found, evaluation of the effects of these errors
should be done during or after the survey.
Considerations
Remediation
Echo sounder manufacturers should provide detailed diagnostic and evaluation routines.
These routines should be used to identify and evaluate the problem.
For the EK500, survey operations should be suspended if the ‘Test’ values are out of
tolerance (refer to the Remediation section under Calibrations). After the problem is resolved,
the survey can continue.
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