The National Institute of Water and Atmospheric Research says it may be possible to breed a species of giant whitebait in captivity.
NIWA scientists released 30 of the native kokopu species into a stream north of Auckland in December each fitted with a tiny transponder.
None of the fish could be located in March, as water ran low, caused by the drought.
But 11 kokopu which are about 20cm long have returned to the research site in Orewa.
NIWA says the experiment suggests it may be possible to breed the species in captivity.