Many large oceanic fishes migrate seasonally between New Zealand and subtropical or tropical waters of the south-west Pacific. Commercial catch data and tagging data were used to determine the timing and routes of the migrations of some of these species, providing new insights into their behaviour and habitats. Albacore tuna (Thunnus alalunga) and skipjack tuna (Katsuwonus pelamis) are caught around New Zealand in summer and return to the tropics in autumn. Other large tropical oceanic species such as whale shark (Rhincodon typus), oceanic whitetip shark (Carcharhinus longimanus), tiger shark (Galeocerdo cuvier), giant manta ray (Manta birostris), wahoo (Acanthocybium solandri), and yellowfin tuna (T. albacares) appear in northern North Island waters in summer, and are presumed to migrate between the tropical Pacific and New Zealand. Electronically tagged juvenile shortfin mako sharks (Isurus oxyrinchus), spinetail devilrays (Mobula japanica), striped marlin (Kajikia audax) and broadbill swordfish (Xiphias gladius) migrated from northern New Zealand to the tropical South Pacific and the Kermadec Ridge. Great white sharks (Carcharodon carcharias) migrated from southern New Zealand to the tropical South Pacific and north-eastern Australia in winter–spring. The movement of large numbers of many species of large-bodied teleosts and chondrichthyans results in the seasonal transfer of large amounts of biomass between tropical and temperate waters.