Filtration rates of Euphausia superba Dana: under- or overestimates?
Filtration rates of adolescent Euphausia superba obtained by both constant volume and flow-through techniques are presented. Filtration rate data for a range of particle sizes are presented. An increase in the number of large particles in the water by enrichment with artificial microcapsules results in a shift of the filtration rate efficiency to a larger size range. This is expressed comparatively by the calculation of selection indices and discussed in terms of the filtration mechanism of krill. A marked difference between the values for filtration rates of krill is found when data from constant volume and flow-through techniques are compared. This is examined by comparison with other published data and alternative estimates of filtration rate are extrapolated from oxygen consumption values, energetics data, and filtering basket sweep frequency. The proposed high level of filtration rate for krill is discussed in relation to the filtration mechanism.