On influence of acoustic survey methodology improvement on krill biomass estimation. (A comparison of results of acoustic surveys based on single-frequency and double-frequency algorithms)

Substantial improvements in data collection and analytical methodologies of acoustic krill surveys have taken place for the recent twenty years. It has been attempted to determine the influence of such improvements on krill biomass estimation. The letter seems to become useful in comparative analysis of krill biomass data from the results of different acoustic surveys.
There have been presented the results of krill biomass comparative estimation by single-frequency and double-frequency algorithms that were obtained by processing data on Russian R/V ATLANTIDA surveying in 48.4 Subarea according to CCAMLR 2000 Krill Survey .
It has been demonstrated that application of different methods to krill species identification realized by single-frequency and double-frequency algorithms could cause a marked difference in krill biomass estimates. A difference was more than 1.8 times in the case under consideration.
Judging from significant differences in biomass estimates attributed to only introducing a new method of krill species identification, one may suggest that other improvements for recent twenty years could also have a considerable influence on biomass estimates obtained . Therefore. it is expected that the analysis of interannual and interseasonal krill biomass variability by results of acoustic survey is to be done taking into account improvements in data collection and analytical methodologies.
One may not exclude that differences in FIBEX-1981 and CCAMLR-2000 krill biomass estimations are rather attributed to the improvements in acoustic sampling and processing survey data than to the variations in krill stock of Subarea 48.