This project developed a food-web model to explore the potential ecosystem effects of changes to small and medium-sized pelagic fish (including jack mackerels, anchovy, pilchards, sprat, yelloweye mullet, blue mackerel, yellow-tailed scad/kōheru) in the Hauraki Gulf. We found that the response of the ecosystem to changes in the abundances of pelagic fishes depended strongly on the extent to which top predators (seabirds, whales/dolphins, fish) are flexible in their diets.