Modeling Interannual Krill Availability (MIKA) in the Central-Northern California Current, 1990–2009

Krill are a main food for many marine species and, because of this, krill shortages can have a profound effect on certain fishes and seabird chick populations. In this project, researchers are seeking to link krill distributions to fish recruitment and survivorship using physical oceanographic data and direct measurements of nutrients, plankton and zooplankton concentrations in the central-northern California Current ecosystem. Output from the model is now being analyzed and compared to acoustically derived estimates of krill availability and to direct observations of predator recruitment and survival (for species such as salmon, sardine and rockfish). The modeling work has also included a 20-year hindcast of ocean conditions vis-à-vis an existing “oceanographic-ecosystem-krill” model adapted and calibrated with field observations from 1990 to 2009. The hypothesis is that measured krill parameters are positively correlated with each other and to higher trophic level (i.e., fisheries) productivity. Results will be of direct application to ecosystem-based fisheries management and to explaining boom-bust cycles in salmon numbers and seabird reproductive success.