a,b, Automatic-identification-systems (AIS)-derived annual vessel-days for Kiribati (a) and for all of the PNA (b) by 318 tuna purse seine vessels. Annual effort is broken down by displaced (n = 64) and non-displaced (n = 254) vessels. The dashed horizontal lines represent the total allowable vessel-days in Kiribati (11,000 vessel-days (ref. 30)) and the PNA (45,000 vessel-days). c, Annual revenue from fishing licence fees by country and year (2008–2016). d, The correspondence between FFA-reported revenues and AIS-derived vessel-day observations (2012–2016). The dashed line in d represents a line of best fit, and the shaded area represents the s.e. around the regression. The colours in c and d represent ISO3 country codes for PNA members.