Using different sources of krill length frequency to convert acoustic backscatter to estimates of krill biomass in Subarea 48.3

Krill length frequency data is essential to convert acoustic signal to krill biomass. There are several sources of krill length frequency data collected by the fishery, monitoring programmes and scientific research cruises. However, there is an inherent degree of bias with all sampling systems, and it is unclear what effect these are likely to have on acoustic estimates of krill biomass. In addition, krill length data are often collected in limited locations and seasons, whereas the use of autonomous systems requires data that spans longer time scales. Here we investigate the effect of using krill length frequency data from a range of krill samplers in Area 48.3, including fishery observers, scientific net samples, and higher predator diet data, to determine the effect of the method of data acquisition on the conversion factor used to convert acoustic signal to krill biomass.