Some large migratory whales might stop passing through New Zealand's warming coastal waters, because there'll be less food - like phytoplankton - available.
But tropical and subtropical marine mammals might take their place -- increasing competition for the dwindling food supplies.
Marine scientist Jim Roberts from Anemone consultants co-authored a report for the Department of Conservation on how climate change might affect our marine mammals.
Dr Roberts spoke to Māni Dunlop about what the future might hold.
