Source:Â NIWA A lack of information about New Zealand oceanic shark populations is making it difficult to assess how well they are doing, says a NIWA researcher. New research published in premier science journal Nature last week, with input from NIWA, showed the global population of oceanic sharks and rays has declined by more than 70 per cent in the past 50 years, with ongoing decline likely to lead to the extinction of some species. NIWA fisheries scientist Dr Brit Finucci says New Zealand waters are home to about 113 shark species and their relatives, of which 20 are considered oceanic, meaning they spend most of their time in the open ocean.