Global Overfishing? Using Indicators as Measures of Ocean Health

The Sea Around Us project maintains a global database of spatially allocated marine catch, landed values, fishing effort, biodiversity, and related features, which is unique in that it is global, and is therefore the key source of spatial fisheries information used in numerous scientific studies.  This database is instrumental in developing various indicators of the impact of fishing at regional and global scales such as global catch-per-unit-effort (CPUE), fisheries subsidies relative to the landed value of the catch, the marine trophic level of the catch, and the proportion of fish stocks in an overfished or collapsed state.  These indicators are crucial to an evaluation of the health of the ocean both because fishing heavily impacts marine ecosystems and because these indicators can be calculated at a number of different spatial scales. 

As a means of addressing the question of global overfishing, newly conceived ‘Stock-Catch Status Plots’ are presented, which document graphically, both the increase in the number of stock that have moved from fully exploited to overexploited and collapsed stages, and the relative biomass of fish extracted from stocks in these various phases.  Additionally we analyze progression time of the number of stocks within each fishery stage, and show that generally there has been an increase in the speed at which stocks are classified as ‘overexploited’ and ‘collapsed.’  These preliminary results indicate that overfishing is likely to continue to be a problem for more stocks. Despite this, there have been increases in the number and biomass of stocks that have been rebuilt.