A note on relating krill CPUE measures to abundance trends

A crude mathematical framework is developed to describe krill abundance in terms of selected parameters of various aggregation behaviours exhibited by krill (Euphausia superba Dana). The relationship of combinations of these parameters to various possible measures of catch-per-unit-effort (CPUE) for the Antarctic krill fishery is considered. The combined index of catch-per-hour of trawling divided by average inter-concentration search time is suggested as a possible measure of krill abundance; such an index should be stratified both spatially and by krill aggregation type - this has implications for routine data collection. Models should be constructed to investigate how substantial non-linearities in the relationship between the index and krill abundance might be.