Past studies in the Pitcairn Islands exclusive economic zone concur that fish stocks are low and that large-scale commercial fishing is not economically viable. Pitcairn lies in an area of the Pacific that is low in nutrients and therefore lacks the conditions necessary to support commercially significant fish biomass. Although it is possible that the available biomass for tuna may change in the future due to climate change, there is little evidence upon which to make a solid prediction and other climate change related factors may in any case preclude this from happening. Furthermore, evidence from fisheries elsewhere shows that the sustainability of stocks can only be ensured through the use of on-board observers to monitor all activities and catches. This is economically viable only in non-marginal fishing areas, which therefore precludes Pitcairn waters.