Krill (Euphausia) represents, in all systems where it occurs, a major element of the diet of commercial fishes, and/or of marine mammals, and would be an important group to study even if they had no direct use as feedstock for mariculture. The biomass and dynamics of krill are difficult to estimate directly using direct sampling or acoustic methods, and it is proposed that these can be inferred indirectly based on the predation rates of krill consumers, and estimates of the production/biomass ratio of krill. The mass-balance approach implemented in the ECOPATH 2 software can be used for this, and an application example is presented, pertaining to the Georgia Strait, British Columbia, for which a trophic model has recently been constructed. It is suggested that such estimates of biomass will compare favourably, both in precision and accuracy, with estimates extrapolated from catch samples, or from hydroacoustics. (D.B.O.).